misc: mic: SCIF DMA and CPU copy interface

SCIF allows users to read from or write to registered remote memory
via CPU copies or DMA. The API verifies that both local and remote
windows are valid before initiating the CPU or DMA transfers. SCIF has
optimized algorithms for handling byte aligned as well as cache line
aligned DMA engines. A registration cache is maintained to avoid the
overhead of pinning pages repeatedly if buffers are reused. The
registration cache is invalidated upon receipt of MMU notifier
callbacks. SCIF windows are destroyed and the pages are unpinned only
once all prior DMAs initiated using that window are drained. Users can
request synchronous DMA operations as well as tail byte ordering if
required. CPU copies are always performed synchronously.

Reviewed-by: Ashutosh Dixit <[e-mail]>
Reviewed-by: Nikhil Rao <[e-mail]>
Signed-off-by: Sudeep Dutt <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/mic/scif/scif_dma.c

···
+/*
+ * Intel MIC Platform Software Stack (MPSS)
+ *
+ * Copyright(c) 2015 Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * Intel SCIF driver.
+ *
+ */
+#include "scif_main.h"
+#include "scif_map.h"
+
+/*
+ * struct scif_dma_comp_cb - SCIF DMA completion callback
+ *
+ * @dma_completion_func: DMA completion callback
+ * @cb_cookie: DMA completion callback cookie
+ * @temp_buf: Temporary buffer
+ * @temp_buf_to_free: Temporary buffer to be freed
+ * @is_cache: Is a kmem_cache allocated buffer
+ * @dst_offset: Destination registration offset
+ * @dst_window: Destination registration window
+ * @len: Length of the temp buffer
+ * @temp_phys: DMA address of the temp buffer
+ * @sdev: The SCIF device
+ * @header_padding: padding for cache line alignment
+ */
+struct scif_dma_comp_cb {
+	void (*dma_completion_func)(void *cookie);
+	void *cb_cookie;
+	u8 *temp_buf;
+	u8 *temp_buf_to_free;
+	bool is_cache;
+	s64 dst_offset;
+	struct scif_window *dst_window;
+	size_t len;
+	dma_addr_t temp_phys;
+	struct scif_dev *sdev;
+	int header_padding;
+};
+
+/**
+ * struct scif_copy_work - Work for DMA copy
+ *
+ * @src_offset: Starting source offset
+ * @dst_offset: Starting destination offset
+ * @src_window: Starting src registered window
+ * @dst_window: Starting dst registered window
+ * @loopback: true if this is a loopback DMA transfer
+ * @len: Length of the transfer
+ * @comp_cb: DMA copy completion callback
+ * @remote_dev: The remote SCIF peer device
+ * @fence_type: polling or interrupt based
+ * @ordered: is this a tail byte ordered DMA transfer
+ */
+struct scif_copy_work {
+	s64 src_offset;
+	s64 dst_offset;
+	struct scif_window *src_window;
+	struct scif_window *dst_window;
+	int loopback;
+	size_t len;
+	struct scif_dma_comp_cb   *comp_cb;
+	struct scif_dev	*remote_dev;
+	int fence_type;
+	bool ordered;
+};
+
+#ifndef list_entry_next
+#define list_entry_next(pos, member) \
+	list_entry(pos->member.next, typeof(*pos), member)
+#endif
+
+/**
+ * scif_reserve_dma_chan:
+ * @ep: Endpoint Descriptor.
+ *
+ * This routine reserves a DMA channel for a particular
+ * endpoint. All DMA transfers for an endpoint are always
+ * programmed on the same DMA channel.
+ */
+int scif_reserve_dma_chan(struct scif_endpt *ep)
+{
+	int err = 0;
+	struct scif_dev *scifdev;
+	struct scif_hw_dev *sdev;
+	struct dma_chan *chan;
+
+	/* Loopback DMAs are not supported on the management node */
+	if (!scif_info.nodeid && scifdev_self(ep->remote_dev))
+		return 0;
+	if (scif_info.nodeid)
+		scifdev = &scif_dev[0];
+	else
+		scifdev = ep->remote_dev;
+	sdev = scifdev->sdev;
+	if (!sdev->num_dma_ch)
+		return -ENODEV;
+	chan = sdev->dma_ch[scifdev->dma_ch_idx];
+	scifdev->dma_ch_idx = (scifdev->dma_ch_idx + 1) % sdev->num_dma_ch;
+	mutex_lock(&ep->rma_info.rma_lock);
+	ep->rma_info.dma_chan = chan;
+	mutex_unlock(&ep->rma_info.rma_lock);
+	return err;
+}
+
+#ifdef CONFIG_MMU_NOTIFIER
+/**
+ * scif_rma_destroy_tcw:
+ *
+ * This routine destroys temporary cached windows
+ */
+static
+void __scif_rma_destroy_tcw(struct scif_mmu_notif *mmn,
+			    struct scif_endpt *ep,
+			    u64 start, u64 len)
+{
+	struct list_head *item, *tmp;
+	struct scif_window *window;
+	u64 start_va, end_va;
+	u64 end = start + len;
+
+	if (end <= start)
+		return;
+
+	list_for_each_safe(item, tmp, &mmn->tc_reg_list) {
+		window = list_entry(item, struct scif_window, list);
+		ep = (struct scif_endpt *)window->ep;
+		if (!len)
+			break;
+		start_va = window->va_for_temp;
+		end_va = start_va + (window->nr_pages << PAGE_SHIFT);
+		if (start < start_va && end <= start_va)
+			break;
+		if (start >= end_va)
+			continue;
+		__scif_rma_destroy_tcw_helper(window);
+	}
+}
+
+static void scif_rma_destroy_tcw(struct scif_mmu_notif *mmn, u64 start, u64 len)
+{
+	struct scif_endpt *ep = mmn->ep;
+
+	spin_lock(&ep->rma_info.tc_lock);
+	__scif_rma_destroy_tcw(mmn, ep, start, len);
+	spin_unlock(&ep->rma_info.tc_lock);
+}
+
+static void scif_rma_destroy_tcw_ep(struct scif_endpt *ep)
+{
+	struct list_head *item, *tmp;
+	struct scif_mmu_notif *mmn;
+
+	list_for_each_safe(item, tmp, &ep->rma_info.mmn_list) {
+		mmn = list_entry(item, struct scif_mmu_notif, list);
+		scif_rma_destroy_tcw(mmn, 0, ULONG_MAX);
+	}
+}
+
+static void __scif_rma_destroy_tcw_ep(struct scif_endpt *ep)
+{
+	struct list_head *item, *tmp;
+	struct scif_mmu_notif *mmn;
+
+	spin_lock(&ep->rma_info.tc_lock);
+	list_for_each_safe(item, tmp, &ep->rma_info.mmn_list) {
+		mmn = list_entry(item, struct scif_mmu_notif, list);
+		__scif_rma_destroy_tcw(mmn, ep, 0, ULONG_MAX);
+	}
+	spin_unlock(&ep->rma_info.tc_lock);
+}
+
+static bool scif_rma_tc_can_cache(struct scif_endpt *ep, size_t cur_bytes)
+{
+	if ((cur_bytes >> PAGE_SHIFT) > scif_info.rma_tc_limit)
+		return false;
+	if ((atomic_read(&ep->rma_info.tcw_total_pages)
+			+ (cur_bytes >> PAGE_SHIFT)) >
+			scif_info.rma_tc_limit) {
+		dev_info(scif_info.mdev.this_device,
+			 "%s %d total=%d, current=%zu reached max\n",
+			 __func__, __LINE__,
+			 atomic_read(&ep->rma_info.tcw_total_pages),
+			 (1 + (cur_bytes >> PAGE_SHIFT)));
+		scif_rma_destroy_tcw_invalid();
+		__scif_rma_destroy_tcw_ep(ep);
+	}
+	return true;
+}
+
+static void scif_mmu_notifier_release(struct mmu_notifier *mn,
+				      struct mm_struct *mm)
+{
+	struct scif_mmu_notif	*mmn;
+
+	mmn = container_of(mn, struct scif_mmu_notif, ep_mmu_notifier);
+	scif_rma_destroy_tcw(mmn, 0, ULONG_MAX);
+	schedule_work(&scif_info.misc_work);
+}
+
+static void scif_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
+					      struct mm_struct *mm,
+					      unsigned long address)
+{
+	struct scif_mmu_notif	*mmn;
+
+	mmn = container_of(mn, struct scif_mmu_notif, ep_mmu_notifier);
+	scif_rma_destroy_tcw(mmn, address, PAGE_SIZE);
+}
+
+static void scif_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
+						     struct mm_struct *mm,
+						     unsigned long start,
+						     unsigned long end)
+{
+	struct scif_mmu_notif	*mmn;
+
+	mmn = container_of(mn, struct scif_mmu_notif, ep_mmu_notifier);
+	scif_rma_destroy_tcw(mmn, start, end - start);
+}
+
+static void scif_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
+						   struct mm_struct *mm,
+						   unsigned long start,
+						   unsigned long end)
+{
+	/*
+	 * Nothing to do here, everything needed was done in
+	 * invalidate_range_start.
+	 */
+}
+
+static const struct mmu_notifier_ops scif_mmu_notifier_ops = {
+	.release = scif_mmu_notifier_release,
+	.clear_flush_young = NULL,
+	.invalidate_page = scif_mmu_notifier_invalidate_page,
+	.invalidate_range_start = scif_mmu_notifier_invalidate_range_start,
+	.invalidate_range_end = scif_mmu_notifier_invalidate_range_end};
+
+static void scif_ep_unregister_mmu_notifier(struct scif_endpt *ep)
+{
+	struct scif_endpt_rma_info *rma = &ep->rma_info;
+	struct scif_mmu_notif *mmn = NULL;
+	struct list_head *item, *tmp;
+
+	mutex_lock(&ep->rma_info.mmn_lock);
+	list_for_each_safe(item, tmp, &rma->mmn_list) {
+		mmn = list_entry(item, struct scif_mmu_notif, list);
+		mmu_notifier_unregister(&mmn->ep_mmu_notifier, mmn->mm);
+		list_del(item);
+		kfree(mmn);
+	}
+	mutex_unlock(&ep->rma_info.mmn_lock);
+}
+
+static void scif_init_mmu_notifier(struct scif_mmu_notif *mmn,
+				   struct mm_struct *mm, struct scif_endpt *ep)
+{
+	mmn->ep = ep;
+	mmn->mm = mm;
+	mmn->ep_mmu_notifier.ops = &scif_mmu_notifier_ops;
+	INIT_LIST_HEAD(&mmn->list);
+	INIT_LIST_HEAD(&mmn->tc_reg_list);
+}
+
+static struct scif_mmu_notif *
+scif_find_mmu_notifier(struct mm_struct *mm, struct scif_endpt_rma_info *rma)
+{
+	struct scif_mmu_notif *mmn;
+	struct list_head *item;
+
+	list_for_each(item, &rma->mmn_list) {
+		mmn = list_entry(item, struct scif_mmu_notif, list);
+		if (mmn->mm == mm)
+			return mmn;
+	}
+	return NULL;
+}
+
+static struct scif_mmu_notif *
+scif_add_mmu_notifier(struct mm_struct *mm, struct scif_endpt *ep)
+{
+	struct scif_mmu_notif *mmn
+		 = kzalloc(sizeof(*mmn), GFP_KERNEL);
+
+	if (!mmn)
+		return ERR_PTR(ENOMEM);
+
+	scif_init_mmu_notifier(mmn, current->mm, ep);
+	if (mmu_notifier_register(&mmn->ep_mmu_notifier,
+				  current->mm)) {
+		kfree(mmn);
+		return ERR_PTR(EBUSY);
+	}
+	list_add(&mmn->list, &ep->rma_info.mmn_list);
+	return mmn;
+}
+
+/*
+ * Called from the misc thread to destroy temporary cached windows and
+ * unregister the MMU notifier for the SCIF endpoint.
+ */
+void scif_mmu_notif_handler(struct work_struct *work)
+{
+	struct list_head *pos, *tmpq;
+	struct scif_endpt *ep;
+restart:
+	scif_rma_destroy_tcw_invalid();
+	spin_lock(&scif_info.rmalock);
+	list_for_each_safe(pos, tmpq, &scif_info.mmu_notif_cleanup) {
+		ep = list_entry(pos, struct scif_endpt, mmu_list);
+		list_del(&ep->mmu_list);
+		spin_unlock(&scif_info.rmalock);
+		scif_rma_destroy_tcw_ep(ep);
+		scif_ep_unregister_mmu_notifier(ep);
+		goto restart;
+	}
+	spin_unlock(&scif_info.rmalock);
+}
+
+static bool scif_is_set_reg_cache(int flags)
+{
+	return !!(flags & SCIF_RMA_USECACHE);
+}
+#else
+static struct scif_mmu_notif *
+scif_find_mmu_notifier(struct mm_struct *mm,
+		       struct scif_endpt_rma_info *rma)
+{
+	return NULL;
+}
+
+static struct scif_mmu_notif *
+scif_add_mmu_notifier(struct mm_struct *mm, struct scif_endpt *ep)
+{
+	return NULL;
+}
+
+void scif_mmu_notif_handler(struct work_struct *work)
+{
+}
+
+static bool scif_is_set_reg_cache(int flags)
+{
+	return false;
+}
+
+static bool scif_rma_tc_can_cache(struct scif_endpt *ep, size_t cur_bytes)
+{
+	return false;
+}
+#endif
+
+/**
+ * scif_register_temp:
+ * @epd: End Point Descriptor.
+ * @addr: virtual address to/from which to copy
+ * @len: length of range to copy
+ * @out_offset: computed offset returned by reference.
+ * @out_window: allocated registered window returned by reference.
+ *
+ * Create a temporary registered window. The peer will not know about this
+ * window. This API is used for scif_vreadfrom()/scif_vwriteto() API's.
+ */
+static int
+scif_register_temp(scif_epd_t epd, unsigned long addr, size_t len, int prot,
+		   off_t *out_offset, struct scif_window **out_window)
+{
+	struct scif_endpt *ep = (struct scif_endpt *)epd;
+	int err;
+	scif_pinned_pages_t pinned_pages;
+	size_t aligned_len;
+
+	aligned_len = ALIGN(len, PAGE_SIZE);
+
+	err = __scif_pin_pages((void *)(addr & PAGE_MASK),
+			       aligned_len, &prot, 0, &pinned_pages);
+	if (err)
+		return err;
+
+	pinned_pages->prot = prot;
+
+	/* Compute the offset for this registration */
+	err = scif_get_window_offset(ep, 0, 0,
+				     aligned_len >> PAGE_SHIFT,
+				     (s64 *)out_offset);
+	if (err)
+		goto error_unpin;
+
+	/* Allocate and prepare self registration window */
+	*out_window = scif_create_window(ep, aligned_len >> PAGE_SHIFT,
+					*out_offset, true);
+	if (!*out_window) {
+		scif_free_window_offset(ep, NULL, *out_offset);
+		err = -ENOMEM;
+		goto error_unpin;
+	}
+
+	(*out_window)->pinned_pages = pinned_pages;
+	(*out_window)->nr_pages = pinned_pages->nr_pages;
+	(*out_window)->prot = pinned_pages->prot;
+
+	(*out_window)->va_for_temp = addr & PAGE_MASK;
+	err = scif_map_window(ep->remote_dev, *out_window);
+	if (err) {
+		/* Something went wrong! Rollback */
+		scif_destroy_window(ep, *out_window);
+		*out_window = NULL;
+	} else {
+		*out_offset |= (addr - (*out_window)->va_for_temp);
+	}
+	return err;
+error_unpin:
+	if (err)
+		dev_err(&ep->remote_dev->sdev->dev,
+			"%s %d err %d\n", __func__, __LINE__, err);
+	scif_unpin_pages(pinned_pages);
+	return err;
+}
+
+#define SCIF_DMA_TO (3 * HZ)
+
+/*
+ * scif_sync_dma - Program a DMA without an interrupt descriptor
+ *
+ * @dev - The address of the pointer to the device instance used
+ * for DMA registration.
+ * @chan - DMA channel to be used.
+ * @sync_wait: Wait for DMA to complete?
+ *
+ * Return 0 on success and -errno on error.
+ */
+static int scif_sync_dma(struct scif_hw_dev *sdev, struct dma_chan *chan,
+			 bool sync_wait)
+{
+	int err = 0;
+	struct dma_async_tx_descriptor *tx = NULL;
+	enum dma_ctrl_flags flags = DMA_PREP_FENCE;
+	dma_cookie_t cookie;
+	struct dma_device *ddev;
+
+	if (!chan) {
+		err = -EIO;
+		dev_err(&sdev->dev, "%s %d err %d\n",
+			__func__, __LINE__, err);
+		return err;
+	}
+	ddev = chan->device;
+
+	tx = ddev->device_prep_dma_memcpy(chan, 0, 0, 0, flags);
+	if (!tx) {
+		err = -ENOMEM;
+		dev_err(&sdev->dev, "%s %d err %d\n",
+			__func__, __LINE__, err);
+		goto release;
+	}
+	cookie = tx->tx_submit(tx);
+
+	if (dma_submit_error(cookie)) {
+		err = -ENOMEM;
+		dev_err(&sdev->dev, "%s %d err %d\n",
+			__func__, __LINE__, err);
+		goto release;
+	}
+	if (!sync_wait) {
+		dma_async_issue_pending(chan);
+	} else {
+		if (dma_sync_wait(chan, cookie) == DMA_COMPLETE) {
+			err = 0;
+		} else {
+			err = -EIO;
+			dev_err(&sdev->dev, "%s %d err %d\n",
+				__func__, __LINE__, err);
+		}
+	}
+release:
+	return err;
+}
+
+static void scif_dma_callback(void *arg)
+{
+	struct completion *done = (struct completion *)arg;
+
+	complete(done);
+}
+
+#define SCIF_DMA_SYNC_WAIT true
+#define SCIF_DMA_POLL BIT(0)
+#define SCIF_DMA_INTR BIT(1)
+
+/*
+ * scif_async_dma - Program a DMA with an interrupt descriptor
+ *
+ * @dev - The address of the pointer to the device instance used
+ * for DMA registration.
+ * @chan - DMA channel to be used.
+ * Return 0 on success and -errno on error.
+ */
+static int scif_async_dma(struct scif_hw_dev *sdev, struct dma_chan *chan)
+{
+	int err = 0;
+	struct dma_device *ddev;
+	struct dma_async_tx_descriptor *tx = NULL;
+	enum dma_ctrl_flags flags = DMA_PREP_INTERRUPT | DMA_PREP_FENCE;
+	DECLARE_COMPLETION_ONSTACK(done_wait);
+	dma_cookie_t cookie;
+	enum dma_status status;
+
+	if (!chan) {
+		err = -EIO;
+		dev_err(&sdev->dev, "%s %d err %d\n",
+			__func__, __LINE__, err);
+		return err;
+	}
+	ddev = chan->device;
+
+	tx = ddev->device_prep_dma_memcpy(chan, 0, 0, 0, flags);
+	if (!tx) {
+		err = -ENOMEM;
+		dev_err(&sdev->dev, "%s %d err %d\n",
+			__func__, __LINE__, err);
+		goto release;
+	}
+	reinit_completion(&done_wait);
+	tx->callback = scif_dma_callback;
+	tx->callback_param = &done_wait;
+	cookie = tx->tx_submit(tx);
+
+	if (dma_submit_error(cookie)) {
+		err = -ENOMEM;
+		dev_err(&sdev->dev, "%s %d err %d\n",
+			__func__, __LINE__, err);
+		goto release;
+	}
+	dma_async_issue_pending(chan);
+
+	err = wait_for_completion_timeout(&done_wait, SCIF_DMA_TO);
+	if (!err) {
+		err = -EIO;
+		dev_err(&sdev->dev, "%s %d err %d\n",
+			__func__, __LINE__, err);
+		goto release;
+	}
+	err = 0;
+	status = dma_async_is_tx_complete(chan, cookie, NULL, NULL);
+	if (status != DMA_COMPLETE) {
+		err = -EIO;
+		dev_err(&sdev->dev, "%s %d err %d\n",
+			__func__, __LINE__, err);
+		goto release;
+	}
+release:
+	return err;
+}
+
+/*
+ * scif_drain_dma_poll - Drain all outstanding DMA operations for a particular
+ * DMA channel via polling.
+ *
+ * @sdev - The SCIF device
+ * @chan - DMA channel
+ * Return 0 on success and -errno on error.
+ */
+static int scif_drain_dma_poll(struct scif_hw_dev *sdev, struct dma_chan *chan)
+{
+	if (!chan)
+		return -EINVAL;
+	return scif_sync_dma(sdev, chan, SCIF_DMA_SYNC_WAIT);
+}
+
+/*
+ * scif_drain_dma_intr - Drain all outstanding DMA operations for a particular
+ * DMA channel via interrupt based blocking wait.
+ *
+ * @sdev - The SCIF device
+ * @chan - DMA channel
+ * Return 0 on success and -errno on error.
+ */
+int scif_drain_dma_intr(struct scif_hw_dev *sdev, struct dma_chan *chan)
+{
+	if (!chan)
+		return -EINVAL;
+	return scif_async_dma(sdev, chan);
+}
+
+/**
+ * scif_rma_destroy_windows:
+ *
+ * This routine destroys all windows queued for cleanup
+ */
+void scif_rma_destroy_windows(void)
+{
+	struct list_head *item, *tmp;
+	struct scif_window *window;
+	struct scif_endpt *ep;
+	struct dma_chan *chan;
+
+	might_sleep();
+restart:
+	spin_lock(&scif_info.rmalock);
+	list_for_each_safe(item, tmp, &scif_info.rma) {
+		window = list_entry(item, struct scif_window,
+				    list);
+		ep = (struct scif_endpt *)window->ep;
+		chan = ep->rma_info.dma_chan;
+
+		list_del_init(&window->list);
+		spin_unlock(&scif_info.rmalock);
+		if (!chan || !scifdev_alive(ep) ||
+		    !scif_drain_dma_intr(ep->remote_dev->sdev,
+					 ep->rma_info.dma_chan))
+			/* Remove window from global list */
+			window->unreg_state = OP_COMPLETED;
+		else
+			dev_warn(&ep->remote_dev->sdev->dev,
+				 "DMA engine hung?\n");
+		if (window->unreg_state == OP_COMPLETED) {
+			if (window->type == SCIF_WINDOW_SELF)
+				scif_destroy_window(ep, window);
+			else
+				scif_destroy_remote_window(window);
+			atomic_dec(&ep->rma_info.tw_refcount);
+		}
+		goto restart;
+	}
+	spin_unlock(&scif_info.rmalock);
+}
+
+/**
+ * scif_rma_destroy_tcw:
+ *
+ * This routine destroys temporary cached registered windows
+ * which have been queued for cleanup.
+ */
+void scif_rma_destroy_tcw_invalid(void)
+{
+	struct list_head *item, *tmp;
+	struct scif_window *window;
+	struct scif_endpt *ep;
+	struct dma_chan *chan;
+
+	might_sleep();
+restart:
+	spin_lock(&scif_info.rmalock);
+	list_for_each_safe(item, tmp, &scif_info.rma_tc) {
+		window = list_entry(item, struct scif_window, list);
+		ep = (struct scif_endpt *)window->ep;
+		chan = ep->rma_info.dma_chan;
+		list_del_init(&window->list);
+		spin_unlock(&scif_info.rmalock);
+		mutex_lock(&ep->rma_info.rma_lock);
+		if (!chan || !scifdev_alive(ep) ||
+		    !scif_drain_dma_intr(ep->remote_dev->sdev,
+					 ep->rma_info.dma_chan)) {
+			atomic_sub(window->nr_pages,
+				   &ep->rma_info.tcw_total_pages);
+			scif_destroy_window(ep, window);
+			atomic_dec(&ep->rma_info.tcw_refcount);
+		} else {
+			dev_warn(&ep->remote_dev->sdev->dev,
+				 "DMA engine hung?\n");
+		}
+		mutex_unlock(&ep->rma_info.rma_lock);
+		goto restart;
+	}
+	spin_unlock(&scif_info.rmalock);
+}
+
+static inline
+void *_get_local_va(off_t off, struct scif_window *window, size_t len)
+{
+	int page_nr = (off - window->offset) >> PAGE_SHIFT;
+	off_t page_off = off & ~PAGE_MASK;
+	void *va = NULL;
+
+	if (window->type == SCIF_WINDOW_SELF) {
+		struct page **pages = window->pinned_pages->pages;
+
+		va = page_address(pages[page_nr]) + page_off;
+	}
+	return va;
+}
+
+static inline
+void *ioremap_remote(off_t off, struct scif_window *window,
+		     size_t len, struct scif_dev *dev,
+		     struct scif_window_iter *iter)
+{
+	dma_addr_t phys = scif_off_to_dma_addr(window, off, NULL, iter);
+
+	/*
+	 * If the DMA address is not card relative then we need the DMA
+	 * addresses to be an offset into the bar. The aperture base was already
+	 * added so subtract it here since scif_ioremap is going to add it again
+	 */
+	if (!scifdev_self(dev) && window->type == SCIF_WINDOW_PEER &&
+	    dev->sdev->aper && !dev->sdev->card_rel_da)
+		phys = phys - dev->sdev->aper->pa;
+	return scif_ioremap(phys, len, dev);
+}
+
+static inline void
+iounmap_remote(void *virt, size_t size, struct scif_copy_work *work)
+{
+	scif_iounmap(virt, size, work->remote_dev);
+}
+
+/*
+ * Takes care of ordering issue caused by
+ * 1. Hardware:  Only in the case of cpu copy from mgmt node to card
+ * because of WC memory.
+ * 2. Software: If memcpy reorders copy instructions for optimization.
+ * This could happen at both mgmt node and card.
+ */
+static inline void
+scif_ordered_memcpy_toio(char *dst, const char *src, size_t count)
+{
+	if (!count)
+		return;
+
+	memcpy_toio((void __iomem __force *)dst, src, --count);
+	/* Order the last byte with the previous stores */
+	wmb();
+	*(dst + count) = *(src + count);
+}
+
+static inline void scif_unaligned_cpy_toio(char *dst, const char *src,
+					   size_t count, bool ordered)
+{
+	if (ordered)
+		scif_ordered_memcpy_toio(dst, src, count);
+	else
+		memcpy_toio((void __iomem __force *)dst, src, count);
+}
+
+static inline
+void scif_ordered_memcpy_fromio(char *dst, const char *src, size_t count)
+{
+	if (!count)
+		return;
+
+	memcpy_fromio(dst, (void __iomem __force *)src, --count);
+	/* Order the last byte with the previous loads */
+	rmb();
+	*(dst + count) = *(src + count);
+}
+
+static inline void scif_unaligned_cpy_fromio(char *dst, const char *src,
+					     size_t count, bool ordered)
+{
+	if (ordered)
+		scif_ordered_memcpy_fromio(dst, src, count);
+	else
+		memcpy_fromio(dst, (void __iomem __force *)src, count);
+}
+
+#define SCIF_RMA_ERROR_CODE (~(dma_addr_t)0x0)
+
+/*
+ * scif_off_to_dma_addr:
+ * Obtain the dma_addr given the window and the offset.
+ * @window: Registered window.
+ * @off: Window offset.
+ * @nr_bytes: Return the number of contiguous bytes till next DMA addr index.
+ * @index: Return the index of the dma_addr array found.
+ * @start_off: start offset of index of the dma addr array found.
+ * The nr_bytes provides the callee an estimate of the maximum possible
+ * DMA xfer possible while the index/start_off provide faster lookups
+ * for the next iteration.
+ */
+dma_addr_t scif_off_to_dma_addr(struct scif_window *window, s64 off,
+				size_t *nr_bytes, struct scif_window_iter *iter)
+{
+	int i, page_nr;
+	s64 start, end;
+	off_t page_off;
+
+	if (window->nr_pages == window->nr_contig_chunks) {
+		page_nr = (off - window->offset) >> PAGE_SHIFT;
+		page_off = off & ~PAGE_MASK;
+
+		if (nr_bytes)
+			*nr_bytes = PAGE_SIZE - page_off;
+		return window->dma_addr[page_nr] | page_off;
+	}
+	if (iter) {
+		i = iter->index;
+		start = iter->offset;
+	} else {
+		i =  0;
+		start =  window->offset;
+	}
+	for (; i < window->nr_contig_chunks; i++) {
+		end = start + (window->num_pages[i] << PAGE_SHIFT);
+		if (off >= start && off < end) {
+			if (iter) {
+				iter->index = i;
+				iter->offset = start;
+			}
+			if (nr_bytes)
+				*nr_bytes = end - off;
+			return (window->dma_addr[i] + (off - start));
+		}
+		start += (window->num_pages[i] << PAGE_SHIFT);
+	}
+	dev_err(scif_info.mdev.this_device,
+		"%s %d BUG. Addr not found? window %p off 0x%llx\n",
+		__func__, __LINE__, window, off);
+	return SCIF_RMA_ERROR_CODE;
+}
+
+/*
+ * Copy between rma window and temporary buffer
+ */
+static void scif_rma_local_cpu_copy(s64 offset, struct scif_window *window,
+				    u8 *temp, size_t rem_len, bool to_temp)
+{
+	void *window_virt;
+	size_t loop_len;
+	int offset_in_page;
+	s64 end_offset;
+
+	offset_in_page = offset & ~PAGE_MASK;
+	loop_len = PAGE_SIZE - offset_in_page;
+
+	if (rem_len < loop_len)
+		loop_len = rem_len;
+
+	window_virt = _get_local_va(offset, window, loop_len);
+	if (!window_virt)
+		return;
+	if (to_temp)
+		memcpy(temp, window_virt, loop_len);
+	else
+		memcpy(window_virt, temp, loop_len);
+
+	offset += loop_len;
+	temp += loop_len;
+	rem_len -= loop_len;
+
+	end_offset = window->offset +
+		(window->nr_pages << PAGE_SHIFT);
+	while (rem_len) {
+		if (offset == end_offset) {
+			window = list_entry_next(window, list);
+			end_offset = window->offset +
+				(window->nr_pages << PAGE_SHIFT);
+		}
+		loop_len = min(PAGE_SIZE, rem_len);
+		window_virt = _get_local_va(offset, window, loop_len);
+		if (!window_virt)
+			return;
+		if (to_temp)
+			memcpy(temp, window_virt, loop_len);
+		else
+			memcpy(window_virt, temp, loop_len);
+		offset	+= loop_len;
+		temp	+= loop_len;
+		rem_len	-= loop_len;
+	}
+}
+
+/**
+ * scif_rma_completion_cb:
+ * @data: RMA cookie
+ *
+ * RMA interrupt completion callback.
+ */
+static void scif_rma_completion_cb(void *data)
+{
+	struct scif_dma_comp_cb *comp_cb = data;
+
+	/* Free DMA Completion CB. */
+	if (comp_cb->dst_window)
+		scif_rma_local_cpu_copy(comp_cb->dst_offset,
+					comp_cb->dst_window,
+					comp_cb->temp_buf +
+					comp_cb->header_padding,
+					comp_cb->len, false);
+	scif_unmap_single(comp_cb->temp_phys, comp_cb->sdev,
+			  SCIF_KMEM_UNALIGNED_BUF_SIZE);
+	if (comp_cb->is_cache)
+		kmem_cache_free(unaligned_cache,
+				comp_cb->temp_buf_to_free);
+	else
+		kfree(comp_cb->temp_buf_to_free);
+}
+
+/* Copies between temporary buffer and offsets provided in work */
+static int
+scif_rma_list_dma_copy_unaligned(struct scif_copy_work *work,
+				 u8 *temp, struct dma_chan *chan,
+				 bool src_local)
+{
+	struct scif_dma_comp_cb *comp_cb = work->comp_cb;
+	dma_addr_t window_dma_addr, temp_dma_addr;
+	dma_addr_t temp_phys = comp_cb->temp_phys;
+	size_t loop_len, nr_contig_bytes = 0, remaining_len = work->len;
+	int offset_in_ca, ret = 0;
+	s64 end_offset, offset;
+	struct scif_window *window;
+	void *window_virt_addr;
+	size_t tail_len;
+	struct dma_async_tx_descriptor *tx;
+	struct dma_device *dev = chan->device;
+	dma_cookie_t cookie;
+
+	if (src_local) {
+		offset = work->dst_offset;
+		window = work->dst_window;
+	} else {
+		offset = work->src_offset;
+		window = work->src_window;
+	}
+
+	offset_in_ca = offset & (L1_CACHE_BYTES - 1);
+	if (offset_in_ca) {
+		loop_len = L1_CACHE_BYTES - offset_in_ca;
+		loop_len = min(loop_len, remaining_len);
+		window_virt_addr = ioremap_remote(offset, window,
+						  loop_len,
+						  work->remote_dev,
+						  NULL);
+		if (!window_virt_addr)
+			return -ENOMEM;
+		if (src_local)
+			scif_unaligned_cpy_toio(window_virt_addr, temp,
+						loop_len,
+						work->ordered &&
+						!(remaining_len - loop_len));
+		else
+			scif_unaligned_cpy_fromio(temp, window_virt_addr,
+						  loop_len, work->ordered &&
+						  !(remaining_len - loop_len));
+		iounmap_remote(window_virt_addr, loop_len, work);
+
+		offset += loop_len;
+		temp += loop_len;
+		temp_phys += loop_len;
+		remaining_len -= loop_len;
+	}
+
+	offset_in_ca = offset & ~PAGE_MASK;
+	end_offset = window->offset +
+		(window->nr_pages << PAGE_SHIFT);
+
+	tail_len = remaining_len & (L1_CACHE_BYTES - 1);
+	remaining_len -= tail_len;
+	while (remaining_len) {
+		if (offset == end_offset) {
+			window = list_entry_next(window, list);
+			end_offset = window->offset +
+				(window->nr_pages << PAGE_SHIFT);
+		}
+		if (scif_is_mgmt_node())
+			temp_dma_addr = temp_phys;
+		else
+			/* Fix if we ever enable IOMMU on the card */
+			temp_dma_addr = (dma_addr_t)virt_to_phys(temp);
+		window_dma_addr = scif_off_to_dma_addr(window, offset,
+						       &nr_contig_bytes,
+						       NULL);
+		loop_len = min(nr_contig_bytes, remaining_len);
+		if (src_local) {
+			if (work->ordered && !tail_len &&
+			    !(remaining_len - loop_len) &&
+			    loop_len != L1_CACHE_BYTES) {
+				/*
+				 * Break up the last chunk of the transfer into
+				 * two steps. if there is no tail to guarantee
+				 * DMA ordering. SCIF_DMA_POLLING inserts
+				 * a status update descriptor in step 1 which
+				 * acts as a double sided synchronization fence
+				 * for the DMA engine to ensure that the last
+				 * cache line in step 2 is updated last.
+				 */
+				/* Step 1) DMA: Body Length - L1_CACHE_BYTES. */
+				tx =
+				dev->device_prep_dma_memcpy(chan,
+							    window_dma_addr,
+							    temp_dma_addr,
+							    loop_len -
+							    L1_CACHE_BYTES,
+							    DMA_PREP_FENCE);
+				if (!tx) {
+					ret = -ENOMEM;
+					goto err;
+				}
+				cookie = tx->tx_submit(tx);
+				if (dma_submit_error(cookie)) {
+					ret = -ENOMEM;
+					goto err;
+				}
+				dma_async_issue_pending(chan);
+				offset += (loop_len - L1_CACHE_BYTES);
+				temp_dma_addr += (loop_len - L1_CACHE_BYTES);
+				window_dma_addr += (loop_len - L1_CACHE_BYTES);
+				remaining_len -= (loop_len - L1_CACHE_BYTES);
+				loop_len = remaining_len;
+
+				/* Step 2) DMA: L1_CACHE_BYTES */
+				tx =
+				dev->device_prep_dma_memcpy(chan,
+							    window_dma_addr,
+							    temp_dma_addr,
+							    loop_len, 0);
+				if (!tx) {
+					ret = -ENOMEM;
+					goto err;
+				}
+				cookie = tx->tx_submit(tx);
+				if (dma_submit_error(cookie)) {
+					ret = -ENOMEM;
+					goto err;
+				}
+				dma_async_issue_pending(chan);
+			} else {
+				tx =
+				dev->device_prep_dma_memcpy(chan,
+							    window_dma_addr,
+							    temp_dma_addr,
+							    loop_len, 0);
+				if (!tx) {
+					ret = -ENOMEM;
+					goto err;
+				}
+				cookie = tx->tx_submit(tx);
+				if (dma_submit_error(cookie)) {
+					ret = -ENOMEM;
+					goto err;
+				}
+				dma_async_issue_pending(chan);
+			}
+		} else {
+			tx = dev->device_prep_dma_memcpy(chan, temp_dma_addr,
+					window_dma_addr, loop_len, 0);
+			if (!tx) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			cookie = tx->tx_submit(tx);
+			if (dma_submit_error(cookie)) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			dma_async_issue_pending(chan);
+		}
+		if (ret < 0)
+			goto err;
+		offset += loop_len;
+		temp += loop_len;
+		temp_phys += loop_len;
+		remaining_len -= loop_len;
+		offset_in_ca = 0;
+	}
+	if (tail_len) {
+		if (offset == end_offset) {
+			window = list_entry_next(window, list);
+			end_offset = window->offset +
+				(window->nr_pages << PAGE_SHIFT);
+		}
+		window_virt_addr = ioremap_remote(offset, window, tail_len,
+						  work->remote_dev,
+						  NULL);
+		if (!window_virt_addr)
+			return -ENOMEM;
+		/*
+		 * The CPU copy for the tail bytes must be initiated only once
+		 * previous DMA transfers for this endpoint have completed
+		 * to guarantee ordering.
+		 */
+		if (work->ordered) {
+			struct scif_dev *rdev = work->remote_dev;
+
+			ret = scif_drain_dma_intr(rdev->sdev, chan);
+			if (ret)
+				return ret;
+		}
+		if (src_local)
+			scif_unaligned_cpy_toio(window_virt_addr, temp,
+						tail_len, work->ordered);
+		else
+			scif_unaligned_cpy_fromio(temp, window_virt_addr,
+						  tail_len, work->ordered);
+		iounmap_remote(window_virt_addr, tail_len, work);
+	}
+	tx = dev->device_prep_dma_memcpy(chan, 0, 0, 0, DMA_PREP_INTERRUPT);
+	if (!tx) {
+		ret = -ENOMEM;
+		return ret;
+	}
+	tx->callback = &scif_rma_completion_cb;
+	tx->callback_param = comp_cb;
+	cookie = tx->tx_submit(tx);
+
+	if (dma_submit_error(cookie)) {
+		ret = -ENOMEM;
+		return ret;
+	}
+	dma_async_issue_pending(chan);
+	return 0;
+err:
+	dev_err(scif_info.mdev.this_device,
+		"%s %d Desc Prog Failed ret %d\n",
+		__func__, __LINE__, ret);
+	return ret;
+}
+
+/*
+ * _scif_rma_list_dma_copy_aligned:
+ *
+ * Traverse all the windows and perform DMA copy.
+ */
+static int _scif_rma_list_dma_copy_aligned(struct scif_copy_work *work,
+					   struct dma_chan *chan)
+{
+	dma_addr_t src_dma_addr, dst_dma_addr;
+	size_t loop_len, remaining_len, src_contig_bytes = 0;
+	size_t dst_contig_bytes = 0;
+	struct scif_window_iter src_win_iter;
+	struct scif_window_iter dst_win_iter;
+	s64 end_src_offset, end_dst_offset;
+	struct scif_window *src_window = work->src_window;
+	struct scif_window *dst_window = work->dst_window;
+	s64 src_offset = work->src_offset, dst_offset = work->dst_offset;
+	int ret = 0;
+	struct dma_async_tx_descriptor *tx;
+	struct dma_device *dev = chan->device;
+	dma_cookie_t cookie;
+
+	remaining_len = work->len;
+
+	scif_init_window_iter(src_window, &src_win_iter);
+	scif_init_window_iter(dst_window, &dst_win_iter);
+	end_src_offset = src_window->offset +
+		(src_window->nr_pages << PAGE_SHIFT);
+	end_dst_offset = dst_window->offset +
+		(dst_window->nr_pages << PAGE_SHIFT);
+	while (remaining_len) {
+		if (src_offset == end_src_offset) {
+			src_window = list_entry_next(src_window, list);
+			end_src_offset = src_window->offset +
+				(src_window->nr_pages << PAGE_SHIFT);
+			scif_init_window_iter(src_window, &src_win_iter);
+		}
+		if (dst_offset == end_dst_offset) {
+			dst_window = list_entry_next(dst_window, list);
+			end_dst_offset = dst_window->offset +
+				(dst_window->nr_pages << PAGE_SHIFT);
+			scif_init_window_iter(dst_window, &dst_win_iter);
+		}
+
+		/* compute dma addresses for transfer */
+		src_dma_addr = scif_off_to_dma_addr(src_window, src_offset,
+						    &src_contig_bytes,
+						    &src_win_iter);
+		dst_dma_addr = scif_off_to_dma_addr(dst_window, dst_offset,
+						    &dst_contig_bytes,
+						    &dst_win_iter);
+		loop_len = min(src_contig_bytes, dst_contig_bytes);
+		loop_len = min(loop_len, remaining_len);
+		if (work->ordered && !(remaining_len - loop_len)) {
+			/*
+			 * Break up the last chunk of the transfer into two
+			 * steps to ensure that the last byte in step 2 is
+			 * updated last.
+			 */
+			/* Step 1) DMA: Body Length - 1 */
+			tx = dev->device_prep_dma_memcpy(chan, dst_dma_addr,
+							 src_dma_addr,
+							 loop_len - 1,
+							 DMA_PREP_FENCE);
+			if (!tx) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			cookie = tx->tx_submit(tx);
+			if (dma_submit_error(cookie)) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			src_offset += (loop_len - 1);
+			dst_offset += (loop_len - 1);
+			src_dma_addr += (loop_len - 1);
+			dst_dma_addr += (loop_len - 1);
+			remaining_len -= (loop_len - 1);
+			loop_len = remaining_len;
+
+			/* Step 2) DMA: 1 BYTES */
+			tx = dev->device_prep_dma_memcpy(chan, dst_dma_addr,
+					src_dma_addr, loop_len, 0);
+			if (!tx) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			cookie = tx->tx_submit(tx);
+			if (dma_submit_error(cookie)) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			dma_async_issue_pending(chan);
+		} else {
+			tx = dev->device_prep_dma_memcpy(chan, dst_dma_addr,
+					src_dma_addr, loop_len, 0);
+			if (!tx) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			cookie = tx->tx_submit(tx);
+			if (dma_submit_error(cookie)) {
+				ret = -ENOMEM;
+				goto err;
+			}
+		}
+		src_offset += loop_len;
+		dst_offset += loop_len;
+		remaining_len -= loop_len;
+	}
+	return ret;
+err:
+	dev_err(scif_info.mdev.this_device,
+		"%s %d Desc Prog Failed ret %d\n",
+		__func__, __LINE__, ret);
+	return ret;
+}
+
+/*
+ * scif_rma_list_dma_copy_aligned:
+ *
+ * Traverse all the windows and perform DMA copy.
+ */
+static int scif_rma_list_dma_copy_aligned(struct scif_copy_work *work,
+					  struct dma_chan *chan)
+{
+	dma_addr_t src_dma_addr, dst_dma_addr;
+	size_t loop_len, remaining_len, tail_len, src_contig_bytes = 0;
+	size_t dst_contig_bytes = 0;
+	int src_cache_off;
+	s64 end_src_offset, end_dst_offset;
+	struct scif_window_iter src_win_iter;
+	struct scif_window_iter dst_win_iter;
+	void *src_virt, *dst_virt;
+	struct scif_window *src_window = work->src_window;
+	struct scif_window *dst_window = work->dst_window;
+	s64 src_offset = work->src_offset, dst_offset = work->dst_offset;
+	int ret = 0;
+	struct dma_async_tx_descriptor *tx;
+	struct dma_device *dev = chan->device;
+	dma_cookie_t cookie;
+
+	remaining_len = work->len;
+	scif_init_window_iter(src_window, &src_win_iter);
+	scif_init_window_iter(dst_window, &dst_win_iter);
+
+	src_cache_off = src_offset & (L1_CACHE_BYTES - 1);
+	if (src_cache_off != 0) {
+		/* Head */
+		loop_len = L1_CACHE_BYTES - src_cache_off;
+		loop_len = min(loop_len, remaining_len);
+		src_dma_addr = __scif_off_to_dma_addr(src_window, src_offset);
+		dst_dma_addr = __scif_off_to_dma_addr(dst_window, dst_offset);
+		if (src_window->type == SCIF_WINDOW_SELF)
+			src_virt = _get_local_va(src_offset, src_window,
+						 loop_len);
+		else
+			src_virt = ioremap_remote(src_offset, src_window,
+						  loop_len,
+						  work->remote_dev, NULL);
+		if (!src_virt)
+			return -ENOMEM;
+		if (dst_window->type == SCIF_WINDOW_SELF)
+			dst_virt = _get_local_va(dst_offset, dst_window,
+						 loop_len);
+		else
+			dst_virt = ioremap_remote(dst_offset, dst_window,
+						  loop_len,
+						  work->remote_dev, NULL);
+		if (!dst_virt) {
+			if (src_window->type != SCIF_WINDOW_SELF)
+				iounmap_remote(src_virt, loop_len, work);
+			return -ENOMEM;
+		}
+		if (src_window->type == SCIF_WINDOW_SELF)
+			scif_unaligned_cpy_toio(dst_virt, src_virt, loop_len,
+						remaining_len == loop_len ?
+						work->ordered : false);
+		else
+			scif_unaligned_cpy_fromio(dst_virt, src_virt, loop_len,
+						  remaining_len == loop_len ?
+						  work->ordered : false);
+		if (src_window->type != SCIF_WINDOW_SELF)
+			iounmap_remote(src_virt, loop_len, work);
+		if (dst_window->type != SCIF_WINDOW_SELF)
+			iounmap_remote(dst_virt, loop_len, work);
+		src_offset += loop_len;
+		dst_offset += loop_len;
+		remaining_len -= loop_len;
+	}
+
+	end_src_offset = src_window->offset +
+		(src_window->nr_pages << PAGE_SHIFT);
+	end_dst_offset = dst_window->offset +
+		(dst_window->nr_pages << PAGE_SHIFT);
+	tail_len = remaining_len & (L1_CACHE_BYTES - 1);
+	remaining_len -= tail_len;
+	while (remaining_len) {
+		if (src_offset == end_src_offset) {
+			src_window = list_entry_next(src_window, list);
+			end_src_offset = src_window->offset +
+				(src_window->nr_pages << PAGE_SHIFT);
+			scif_init_window_iter(src_window, &src_win_iter);
+		}
+		if (dst_offset == end_dst_offset) {
+			dst_window = list_entry_next(dst_window, list);
+			end_dst_offset = dst_window->offset +
+				(dst_window->nr_pages << PAGE_SHIFT);
+			scif_init_window_iter(dst_window, &dst_win_iter);
+		}
+
+		/* compute dma addresses for transfer */
+		src_dma_addr = scif_off_to_dma_addr(src_window, src_offset,
+						    &src_contig_bytes,
+						    &src_win_iter);
+		dst_dma_addr = scif_off_to_dma_addr(dst_window, dst_offset,
+						    &dst_contig_bytes,
+						    &dst_win_iter);
+		loop_len = min(src_contig_bytes, dst_contig_bytes);
+		loop_len = min(loop_len, remaining_len);
+		if (work->ordered && !tail_len &&
+		    !(remaining_len - loop_len)) {
+			/*
+			 * Break up the last chunk of the transfer into two
+			 * steps. if there is no tail to gurantee DMA ordering.
+			 * Passing SCIF_DMA_POLLING inserts a status update
+			 * descriptor in step 1 which acts as a double sided
+			 * synchronization fence for the DMA engine to ensure
+			 * that the last cache line in step 2 is updated last.
+			 */
+			/* Step 1) DMA: Body Length - L1_CACHE_BYTES. */
+			tx = dev->device_prep_dma_memcpy(chan, dst_dma_addr,
+							 src_dma_addr,
+							 loop_len -
+							 L1_CACHE_BYTES,
+							 DMA_PREP_FENCE);
+			if (!tx) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			cookie = tx->tx_submit(tx);
+			if (dma_submit_error(cookie)) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			dma_async_issue_pending(chan);
+			src_offset += (loop_len - L1_CACHE_BYTES);
+			dst_offset += (loop_len - L1_CACHE_BYTES);
+			src_dma_addr += (loop_len - L1_CACHE_BYTES);
+			dst_dma_addr += (loop_len - L1_CACHE_BYTES);
+			remaining_len -= (loop_len - L1_CACHE_BYTES);
+			loop_len = remaining_len;
+
+			/* Step 2) DMA: L1_CACHE_BYTES */
+			tx = dev->device_prep_dma_memcpy(chan, dst_dma_addr,
+							 src_dma_addr,
+							 loop_len, 0);
+			if (!tx) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			cookie = tx->tx_submit(tx);
+			if (dma_submit_error(cookie)) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			dma_async_issue_pending(chan);
+		} else {
+			tx = dev->device_prep_dma_memcpy(chan, dst_dma_addr,
+							 src_dma_addr,
+							 loop_len, 0);
+			if (!tx) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			cookie = tx->tx_submit(tx);
+			if (dma_submit_error(cookie)) {
+				ret = -ENOMEM;
+				goto err;
+			}
+			dma_async_issue_pending(chan);
+		}
+		src_offset += loop_len;
+		dst_offset += loop_len;
+		remaining_len -= loop_len;
+	}
+	remaining_len = tail_len;
+	if (remaining_len) {
+		loop_len = remaining_len;
+		if (src_offset == end_src_offset)
+			src_window = list_entry_next(src_window, list);
+		if (dst_offset == end_dst_offset)
+			dst_window = list_entry_next(dst_window, list);
+
+		src_dma_addr = __scif_off_to_dma_addr(src_window, src_offset);
+		dst_dma_addr = __scif_off_to_dma_addr(dst_window, dst_offset);
+		/*
+		 * The CPU copy for the tail bytes must be initiated only once
+		 * previous DMA transfers for this endpoint have completed to
+		 * guarantee ordering.
+		 */
+		if (work->ordered) {
+			struct scif_dev *rdev = work->remote_dev;
+
+			ret = scif_drain_dma_poll(rdev->sdev, chan);
+			if (ret)
+				return ret;
+		}
+		if (src_window->type == SCIF_WINDOW_SELF)
+			src_virt = _get_local_va(src_offset, src_window,
+						 loop_len);
+		else
+			src_virt = ioremap_remote(src_offset, src_window,
+						  loop_len,
+						  work->remote_dev, NULL);
+		if (!src_virt)
+			return -ENOMEM;
+
+		if (dst_window->type == SCIF_WINDOW_SELF)
+			dst_virt = _get_local_va(dst_offset, dst_window,
+						 loop_len);
+		else
+			dst_virt = ioremap_remote(dst_offset, dst_window,
+						  loop_len,
+						  work->remote_dev, NULL);
+		if (!dst_virt) {
+			if (src_window->type != SCIF_WINDOW_SELF)
+				iounmap_remote(src_virt, loop_len, work);
+			return -ENOMEM;
+		}
+
+		if (src_window->type == SCIF_WINDOW_SELF)
+			scif_unaligned_cpy_toio(dst_virt, src_virt, loop_len,
+						work->ordered);
+		else
+			scif_unaligned_cpy_fromio(dst_virt, src_virt,
+						  loop_len, work->ordered);
+		if (src_window->type != SCIF_WINDOW_SELF)
+			iounmap_remote(src_virt, loop_len, work);
+
+		if (dst_window->type != SCIF_WINDOW_SELF)
+			iounmap_remote(dst_virt, loop_len, work);
+		remaining_len -= loop_len;
+	}
+	return ret;
+err:
+	dev_err(scif_info.mdev.this_device,
+		"%s %d Desc Prog Failed ret %d\n",
+		__func__, __LINE__, ret);
+	return ret;
+}
+
+/*
+ * scif_rma_list_cpu_copy:
+ *
+ * Traverse all the windows and perform CPU copy.
+ */
+static int scif_rma_list_cpu_copy(struct scif_copy_work *work)
+{
+	void *src_virt, *dst_virt;
+	size_t loop_len, remaining_len;
+	int src_page_off, dst_page_off;
+	s64 src_offset = work->src_offset, dst_offset = work->dst_offset;
+	struct scif_window *src_window = work->src_window;
+	struct scif_window *dst_window = work->dst_window;
+	s64 end_src_offset, end_dst_offset;
+	int ret = 0;
+	struct scif_window_iter src_win_iter;
+	struct scif_window_iter dst_win_iter;
+
+	remaining_len = work->len;
+
+	scif_init_window_iter(src_window, &src_win_iter);
+	scif_init_window_iter(dst_window, &dst_win_iter);
+	while (remaining_len) {
+		src_page_off = src_offset & ~PAGE_MASK;
+		dst_page_off = dst_offset & ~PAGE_MASK;
+		loop_len = min(PAGE_SIZE -
+			       max(src_page_off, dst_page_off),
+			       remaining_len);
+
+		if (src_window->type == SCIF_WINDOW_SELF)
+			src_virt = _get_local_va(src_offset, src_window,
+						 loop_len);
+		else
+			src_virt = ioremap_remote(src_offset, src_window,
+						  loop_len,
+						  work->remote_dev,
+						  &src_win_iter);
+		if (!src_virt) {
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		if (dst_window->type == SCIF_WINDOW_SELF)
+			dst_virt = _get_local_va(dst_offset, dst_window,
+						 loop_len);
+		else
+			dst_virt = ioremap_remote(dst_offset, dst_window,
+						  loop_len,
+						  work->remote_dev,
+						  &dst_win_iter);
+		if (!dst_virt) {
+			if (src_window->type == SCIF_WINDOW_PEER)
+				iounmap_remote(src_virt, loop_len, work);
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		if (work->loopback) {
+			memcpy(dst_virt, src_virt, loop_len);
+		} else {
+			if (src_window->type == SCIF_WINDOW_SELF)
+				memcpy_toio((void __iomem __force *)dst_virt,
+					    src_virt, loop_len);
+			else
+				memcpy_fromio(dst_virt,
+					      (void __iomem __force *)src_virt,
+					      loop_len);
+		}
+		if (src_window->type == SCIF_WINDOW_PEER)
+			iounmap_remote(src_virt, loop_len, work);
+
+		if (dst_window->type == SCIF_WINDOW_PEER)
+			iounmap_remote(dst_virt, loop_len, work);
+
+		src_offset += loop_len;
+		dst_offset += loop_len;
+		remaining_len -= loop_len;
+		if (remaining_len) {
+			end_src_offset = src_window->offset +
+				(src_window->nr_pages << PAGE_SHIFT);
+			end_dst_offset = dst_window->offset +
+				(dst_window->nr_pages << PAGE_SHIFT);
+			if (src_offset == end_src_offset) {
+				src_window = list_entry_next(src_window, list);
+				scif_init_window_iter(src_window,
+						      &src_win_iter);
+			}
+			if (dst_offset == end_dst_offset) {
+				dst_window = list_entry_next(dst_window, list);
+				scif_init_window_iter(dst_window,
+						      &dst_win_iter);
+			}
+		}
+	}
+error:
+	return ret;
+}
+
+static int scif_rma_list_dma_copy_wrapper(struct scif_endpt *epd,
+					  struct scif_copy_work *work,
+					  struct dma_chan *chan, off_t loffset)
+{
+	int src_cache_off, dst_cache_off;
+	s64 src_offset = work->src_offset, dst_offset = work->dst_offset;
+	u8 *temp = NULL;
+	bool src_local = true, dst_local = false;
+	struct scif_dma_comp_cb *comp_cb;
+	dma_addr_t src_dma_addr, dst_dma_addr;
+	int err;
+
+	if (is_dma_copy_aligned(chan->device, 1, 1, 1))
+		return _scif_rma_list_dma_copy_aligned(work, chan);
+
+	src_cache_off = src_offset & (L1_CACHE_BYTES - 1);
+	dst_cache_off = dst_offset & (L1_CACHE_BYTES - 1);
+
+	if (dst_cache_off == src_cache_off)
+		return scif_rma_list_dma_copy_aligned(work, chan);
+
+	if (work->loopback)
+		return scif_rma_list_cpu_copy(work);
+	src_dma_addr = __scif_off_to_dma_addr(work->src_window, src_offset);
+	dst_dma_addr = __scif_off_to_dma_addr(work->dst_window, dst_offset);
+	src_local = work->src_window->type == SCIF_WINDOW_SELF;
+	dst_local = work->dst_window->type == SCIF_WINDOW_SELF;
+
+	dst_local = dst_local;
+	/* Allocate dma_completion cb */
+	comp_cb = kzalloc(sizeof(*comp_cb), GFP_KERNEL);
+	if (!comp_cb)
+		goto error;
+
+	work->comp_cb = comp_cb;
+	comp_cb->cb_cookie = comp_cb;
+	comp_cb->dma_completion_func = &scif_rma_completion_cb;
+
+	if (work->len + (L1_CACHE_BYTES << 1) < SCIF_KMEM_UNALIGNED_BUF_SIZE) {
+		comp_cb->is_cache = false;
+		/* Allocate padding bytes to align to a cache line */
+		temp = kmalloc(work->len + (L1_CACHE_BYTES << 1),
+			       GFP_KERNEL);
+		if (!temp)
+			goto free_comp_cb;
+		comp_cb->temp_buf_to_free = temp;
+		/* kmalloc(..) does not guarantee cache line alignment */
+		if (!IS_ALIGNED((u64)temp, L1_CACHE_BYTES))
+			temp = PTR_ALIGN(temp, L1_CACHE_BYTES);
+	} else {
+		comp_cb->is_cache = true;
+		temp = kmem_cache_alloc(unaligned_cache, GFP_KERNEL);
+		if (!temp)
+			goto free_comp_cb;
+		comp_cb->temp_buf_to_free = temp;
+	}
+
+	if (src_local) {
+		temp += dst_cache_off;
+		scif_rma_local_cpu_copy(work->src_offset, work->src_window,
+					temp, work->len, true);
+	} else {
+		comp_cb->dst_window = work->dst_window;
+		comp_cb->dst_offset = work->dst_offset;
+		work->src_offset = work->src_offset - src_cache_off;
+		comp_cb->len = work->len;
+		work->len = ALIGN(work->len + src_cache_off, L1_CACHE_BYTES);
+		comp_cb->header_padding = src_cache_off;
+	}
+	comp_cb->temp_buf = temp;
+
+	err = scif_map_single(&comp_cb->temp_phys, temp,
+			      work->remote_dev, SCIF_KMEM_UNALIGNED_BUF_SIZE);
+	if (err)
+		goto free_temp_buf;
+	comp_cb->sdev = work->remote_dev;
+	if (scif_rma_list_dma_copy_unaligned(work, temp, chan, src_local) < 0)
+		goto free_temp_buf;
+	if (!src_local)
+		work->fence_type = SCIF_DMA_INTR;
+	return 0;
+free_temp_buf:
+	if (comp_cb->is_cache)
+		kmem_cache_free(unaligned_cache, comp_cb->temp_buf_to_free);
+	else
+		kfree(comp_cb->temp_buf_to_free);
+free_comp_cb:
+	kfree(comp_cb);
+error:
+	return -ENOMEM;
+}
+
+/**
+ * scif_rma_copy:
+ * @epd: end point descriptor.
+ * @loffset: offset in local registered address space to/from which to copy
+ * @addr: user virtual address to/from which to copy
+ * @len: length of range to copy
+ * @roffset: offset in remote registered address space to/from which to copy
+ * @flags: flags
+ * @dir: LOCAL->REMOTE or vice versa.
+ * @last_chunk: true if this is the last chunk of a larger transfer
+ *
+ * Validate parameters, check if src/dst registered ranges requested for copy
+ * are valid and initiate either CPU or DMA copy.
+ */
+static int scif_rma_copy(scif_epd_t epd, off_t loffset, unsigned long addr,
+			 size_t len, off_t roffset, int flags,
+			 enum scif_rma_dir dir, bool last_chunk)
+{
+	struct scif_endpt *ep = (struct scif_endpt *)epd;
+	struct scif_rma_req remote_req;
+	struct scif_rma_req req;
+	struct scif_window *local_window = NULL;
+	struct scif_window *remote_window = NULL;
+	struct scif_copy_work copy_work;
+	bool loopback;
+	int err = 0;
+	struct dma_chan *chan;
+	struct scif_mmu_notif *mmn = NULL;
+	bool cache = false;
+	struct device *spdev;
+
+	err = scif_verify_epd(ep);
+	if (err)
+		return err;
+
+	if (flags && !(flags & (SCIF_RMA_USECPU | SCIF_RMA_USECACHE |
+				SCIF_RMA_SYNC | SCIF_RMA_ORDERED)))
+		return -EINVAL;
+
+	loopback = scifdev_self(ep->remote_dev) ? true : false;
+	copy_work.fence_type = ((flags & SCIF_RMA_SYNC) && last_chunk) ?
+				SCIF_DMA_POLL : 0;
+	copy_work.ordered = !!((flags & SCIF_RMA_ORDERED) && last_chunk);
+
+	/* Use CPU for Mgmt node <-> Mgmt node copies */
+	if (loopback && scif_is_mgmt_node()) {
+		flags |= SCIF_RMA_USECPU;
+		copy_work.fence_type = 0x0;
+	}
+
+	cache = scif_is_set_reg_cache(flags);
+
+	remote_req.out_window = &remote_window;
+	remote_req.offset = roffset;
+	remote_req.nr_bytes = len;
+	/*
+	 * If transfer is from local to remote then the remote window
+	 * must be writeable and vice versa.
+	 */
+	remote_req.prot = dir == SCIF_LOCAL_TO_REMOTE ? VM_WRITE : VM_READ;
+	remote_req.type = SCIF_WINDOW_PARTIAL;
+	remote_req.head = &ep->rma_info.remote_reg_list;
+
+	spdev = scif_get_peer_dev(ep->remote_dev);
+	if (IS_ERR(spdev)) {
+		err = PTR_ERR(spdev);
+		return err;
+	}
+
+	if (addr && cache) {
+		mutex_lock(&ep->rma_info.mmn_lock);
+		mmn = scif_find_mmu_notifier(current->mm, &ep->rma_info);
+		if (!mmn)
+			scif_add_mmu_notifier(current->mm, ep);
+		mutex_unlock(&ep->rma_info.mmn_lock);
+		if (IS_ERR(mmn)) {
+			scif_put_peer_dev(spdev);
+			return PTR_ERR(mmn);
+		}
+		cache = cache && !scif_rma_tc_can_cache(ep, len);
+	}
+	mutex_lock(&ep->rma_info.rma_lock);
+	if (addr) {
+		req.out_window = &local_window;
+		req.nr_bytes = ALIGN(len + (addr & ~PAGE_MASK),
+				     PAGE_SIZE);
+		req.va_for_temp = addr & PAGE_MASK;
+		req.prot = (dir == SCIF_LOCAL_TO_REMOTE ?
+			    VM_READ : VM_WRITE | VM_READ);
+		/* Does a valid local window exist? */
+		if (mmn) {
+			spin_lock(&ep->rma_info.tc_lock);
+			req.head = &mmn->tc_reg_list;
+			err = scif_query_tcw(ep, &req);
+			spin_unlock(&ep->rma_info.tc_lock);
+		}
+		if (!mmn || err) {
+			err = scif_register_temp(epd, req.va_for_temp,
+						 req.nr_bytes, req.prot,
+						 &loffset, &local_window);
+			if (err) {
+				mutex_unlock(&ep->rma_info.rma_lock);
+				goto error;
+			}
+			if (!cache)
+				goto skip_cache;
+			atomic_inc(&ep->rma_info.tcw_refcount);
+			atomic_add_return(local_window->nr_pages,
+					  &ep->rma_info.tcw_total_pages);
+			if (mmn) {
+				spin_lock(&ep->rma_info.tc_lock);
+				scif_insert_tcw(local_window,
+						&mmn->tc_reg_list);
+				spin_unlock(&ep->rma_info.tc_lock);
+			}
+		}
+skip_cache:
+		loffset = local_window->offset +
+				(addr - local_window->va_for_temp);
+	} else {
+		req.out_window = &local_window;
+		req.offset = loffset;
+		/*
+		 * If transfer is from local to remote then the self window
+		 * must be readable and vice versa.
+		 */
+		req.prot = dir == SCIF_LOCAL_TO_REMOTE ? VM_READ : VM_WRITE;
+		req.nr_bytes = len;
+		req.type = SCIF_WINDOW_PARTIAL;
+		req.head = &ep->rma_info.reg_list;
+		/* Does a valid local window exist? */
+		err = scif_query_window(&req);
+		if (err) {
+			mutex_unlock(&ep->rma_info.rma_lock);
+			goto error;
+		}
+	}
+
+	/* Does a valid remote window exist? */
+	err = scif_query_window(&remote_req);
+	if (err) {
+		mutex_unlock(&ep->rma_info.rma_lock);
+		goto error;
+	}
+
+	/*
+	 * Prepare copy_work for submitting work to the DMA kernel thread
+	 * or CPU copy routine.
+	 */
+	copy_work.len = len;
+	copy_work.loopback = loopback;
+	copy_work.remote_dev = ep->remote_dev;
+	if (dir == SCIF_LOCAL_TO_REMOTE) {
+		copy_work.src_offset = loffset;
+		copy_work.src_window = local_window;
+		copy_work.dst_offset = roffset;
+		copy_work.dst_window = remote_window;
+	} else {
+		copy_work.src_offset = roffset;
+		copy_work.src_window = remote_window;
+		copy_work.dst_offset = loffset;
+		copy_work.dst_window = local_window;
+	}
+
+	if (flags & SCIF_RMA_USECPU) {
+		scif_rma_list_cpu_copy(&copy_work);
+	} else {
+		chan = ep->rma_info.dma_chan;
+		err = scif_rma_list_dma_copy_wrapper(epd, &copy_work,
+						     chan, loffset);
+	}
+	if (addr && !cache)
+		atomic_inc(&ep->rma_info.tw_refcount);
+
+	mutex_unlock(&ep->rma_info.rma_lock);
+
+	if (last_chunk) {
+		struct scif_dev *rdev = ep->remote_dev;
+
+		if (copy_work.fence_type == SCIF_DMA_POLL)
+			err = scif_drain_dma_poll(rdev->sdev,
+						  ep->rma_info.dma_chan);
+		else if (copy_work.fence_type == SCIF_DMA_INTR)
+			err = scif_drain_dma_intr(rdev->sdev,
+						  ep->rma_info.dma_chan);
+	}
+
+	if (addr && !cache)
+		scif_queue_for_cleanup(local_window, &scif_info.rma);
+	scif_put_peer_dev(spdev);
+	return err;
+error:
+	if (err) {
+		if (addr && local_window && !cache)
+			scif_destroy_window(ep, local_window);
+		dev_err(scif_info.mdev.this_device,
+			"%s %d err %d len 0x%lx\n",
+			__func__, __LINE__, err, len);
+	}
+	scif_put_peer_dev(spdev);
+	return err;
+}
+
+int scif_readfrom(scif_epd_t epd, off_t loffset, size_t len,
+		  off_t roffset, int flags)
+{
+	int err;
+
+	dev_dbg(scif_info.mdev.this_device,
+		"SCIFAPI readfrom: ep %p loffset 0x%lx len 0x%lx offset 0x%lx flags 0x%x\n",
+		epd, loffset, len, roffset, flags);
+	if (scif_unaligned(loffset, roffset)) {
+		while (len > SCIF_MAX_UNALIGNED_BUF_SIZE) {
+			err = scif_rma_copy(epd, loffset, 0x0,
+					    SCIF_MAX_UNALIGNED_BUF_SIZE,
+					    roffset, flags,
+					    SCIF_REMOTE_TO_LOCAL, false);
+			if (err)
+				goto readfrom_err;
+			loffset += SCIF_MAX_UNALIGNED_BUF_SIZE;
+			roffset += SCIF_MAX_UNALIGNED_BUF_SIZE;
+			len -= SCIF_MAX_UNALIGNED_BUF_SIZE;
+		}
+	}
+	err = scif_rma_copy(epd, loffset, 0x0, len,
+			    roffset, flags, SCIF_REMOTE_TO_LOCAL, true);
+readfrom_err:
+	return err;
+}
+EXPORT_SYMBOL_GPL(scif_readfrom);
+
+int scif_writeto(scif_epd_t epd, off_t loffset, size_t len,
+		 off_t roffset, int flags)
+{
+	int err;
+
+	dev_dbg(scif_info.mdev.this_device,
+		"SCIFAPI writeto: ep %p loffset 0x%lx len 0x%lx roffset 0x%lx flags 0x%x\n",
+		epd, loffset, len, roffset, flags);
+	if (scif_unaligned(loffset, roffset)) {
+		while (len > SCIF_MAX_UNALIGNED_BUF_SIZE) {
+			err = scif_rma_copy(epd, loffset, 0x0,
+					    SCIF_MAX_UNALIGNED_BUF_SIZE,
+					    roffset, flags,
+					    SCIF_LOCAL_TO_REMOTE, false);
+			if (err)
+				goto writeto_err;
+			loffset += SCIF_MAX_UNALIGNED_BUF_SIZE;
+			roffset += SCIF_MAX_UNALIGNED_BUF_SIZE;
+			len -= SCIF_MAX_UNALIGNED_BUF_SIZE;
+		}
+	}
+	err = scif_rma_copy(epd, loffset, 0x0, len,
+			    roffset, flags, SCIF_LOCAL_TO_REMOTE, true);
+writeto_err:
+	return err;
+}
+EXPORT_SYMBOL_GPL(scif_writeto);
+
+int scif_vreadfrom(scif_epd_t epd, void *addr, size_t len,
+		   off_t roffset, int flags)
+{
+	int err;
+
+	dev_dbg(scif_info.mdev.this_device,
+		"SCIFAPI vreadfrom: ep %p addr %p len 0x%lx roffset 0x%lx flags 0x%x\n",
+		epd, addr, len, roffset, flags);
+	if (scif_unaligned((off_t __force)addr, roffset)) {
+		if (len > SCIF_MAX_UNALIGNED_BUF_SIZE)
+			flags &= ~SCIF_RMA_USECACHE;
+
+		while (len > SCIF_MAX_UNALIGNED_BUF_SIZE) {
+			err = scif_rma_copy(epd, 0, (u64)addr,
+					    SCIF_MAX_UNALIGNED_BUF_SIZE,
+					    roffset, flags,
+					    SCIF_REMOTE_TO_LOCAL, false);
+			if (err)
+				goto vreadfrom_err;
+			addr += SCIF_MAX_UNALIGNED_BUF_SIZE;
+			roffset += SCIF_MAX_UNALIGNED_BUF_SIZE;
+			len -= SCIF_MAX_UNALIGNED_BUF_SIZE;
+		}
+	}
+	err = scif_rma_copy(epd, 0, (u64)addr, len,
+			    roffset, flags, SCIF_REMOTE_TO_LOCAL, true);
+vreadfrom_err:
+	return err;
+}
+EXPORT_SYMBOL_GPL(scif_vreadfrom);
+
+int scif_vwriteto(scif_epd_t epd, void *addr, size_t len,
+		  off_t roffset, int flags)
+{
+	int err;
+
+	dev_dbg(scif_info.mdev.this_device,
+		"SCIFAPI vwriteto: ep %p addr %p len 0x%lx roffset 0x%lx flags 0x%x\n",
+		epd, addr, len, roffset, flags);
+	if (scif_unaligned((off_t __force)addr, roffset)) {
+		if (len > SCIF_MAX_UNALIGNED_BUF_SIZE)
+			flags &= ~SCIF_RMA_USECACHE;
+
+		while (len > SCIF_MAX_UNALIGNED_BUF_SIZE) {
+			err = scif_rma_copy(epd, 0, (u64)addr,
+					    SCIF_MAX_UNALIGNED_BUF_SIZE,
+					    roffset, flags,
+					    SCIF_LOCAL_TO_REMOTE, false);
+			if (err)
+				goto vwriteto_err;
+			addr += SCIF_MAX_UNALIGNED_BUF_SIZE;
+			roffset += SCIF_MAX_UNALIGNED_BUF_SIZE;
+			len -= SCIF_MAX_UNALIGNED_BUF_SIZE;
+		}
+	}
+	err = scif_rma_copy(epd, 0, (u64)addr, len,
+			    roffset, flags, SCIF_LOCAL_TO_REMOTE, true);
+vwriteto_err:
+	return err;
+}
+EXPORT_SYMBOL_GPL(scif_vwriteto);