tee: add tee_shm_alloc_dma_mem()

Add tee_shm_alloc_dma_mem() to allocate DMA memory. The memory is
represented by a tee_shm object using the new flag TEE_SHM_DMA_MEM to
identify it as DMA memory. The allocated memory will later be lent to
the TEE to be used as protected memory.

Reviewed-by: Sumit Garg <[e-mail]>
Signed-off-by: Jens Wiklander <[e-mail]>

drivers/tee/tee_shm.c

···
 #include <linux/anon_inodes.h>
 #include <linux/device.h>
 #include <linux/dma-buf.h>
+#include <linux/dma-mapping.h>
+#include <linux/highmem.h>
 #include <linux/idr.h>
 #include <linux/io.h>
 #include <linux/mm.h>
···
 #include <linux/tee_core.h>
 #include <linux/uaccess.h>
 #include <linux/uio.h>
-#include <linux/highmem.h>
 #include "tee_private.h"
+
+struct tee_shm_dma_mem {
+	struct tee_shm shm;
+	dma_addr_t dma_addr;
+	struct page *page;
+};
 
 static void shm_put_kernel_pages(struct page **pages, size_t page_count)
 {
···
 {
 	void *p = shm;
 
-	if (shm->flags & TEE_SHM_DMA_BUF) {
+	if (shm->flags & TEE_SHM_DMA_MEM) {
+#if IS_ENABLED(CONFIG_TEE_DMABUF_HEAPS)
+		struct tee_shm_dma_mem *dma_mem;
+
+		dma_mem = container_of(shm, struct tee_shm_dma_mem, shm);
+		p = dma_mem;
+		dma_free_pages(&teedev->dev, shm->size, dma_mem->page,
+			       dma_mem->dma_addr, DMA_BIDIRECTIONAL);
+#endif
+	} else if (shm->flags & TEE_SHM_DMA_BUF) {
 		struct tee_shm_dmabuf_ref *ref;
 
 		ref = container_of(shm, struct tee_shm_dmabuf_ref, shm);
···
 	return shm_alloc_helper(ctx, size, sizeof(long) * 2, flags, -1);
 }
 EXPORT_SYMBOL_GPL(tee_shm_alloc_priv_buf);
+
+#if IS_ENABLED(CONFIG_TEE_DMABUF_HEAPS)
+/**
+ * tee_shm_alloc_dma_mem() - Allocate DMA memory as shared memory object
+ * @ctx:	Context that allocates the shared memory
+ * @page_count:	Number of pages
+ *
+ * The allocated memory is expected to be lent (made inaccessible to the
+ * kernel) to the TEE while it's used and returned (accessible to the
+ * kernel again) before it's freed.
+ *
+ * This function should normally only be used internally in the TEE
+ * drivers.
+ *
+ * @returns a pointer to 'struct tee_shm'
+ */
+struct tee_shm *tee_shm_alloc_dma_mem(struct tee_context *ctx,
+				      size_t page_count)
+{
+	struct tee_device *teedev = ctx->teedev;
+	struct tee_shm_dma_mem *dma_mem;
+	dma_addr_t dma_addr;
+	struct page *page;
+
+	if (!tee_device_get(teedev))
+		return ERR_PTR(-EINVAL);
+
+	page = dma_alloc_pages(&teedev->dev, page_count * PAGE_SIZE,
+			       &dma_addr, DMA_BIDIRECTIONAL, GFP_KERNEL);
+	if (!page)
+		goto err_put_teedev;
+
+	dma_mem = kzalloc(sizeof(*dma_mem), GFP_KERNEL);
+	if (!dma_mem)
+		goto err_free_pages;
+
+	refcount_set(&dma_mem->shm.refcount, 1);
+	dma_mem->shm.ctx = ctx;
+	dma_mem->shm.paddr = page_to_phys(page);
+	dma_mem->dma_addr = dma_addr;
+	dma_mem->page = page;
+	dma_mem->shm.size = page_count * PAGE_SIZE;
+	dma_mem->shm.flags = TEE_SHM_DMA_MEM;
+
+	teedev_ctx_get(ctx);
+
+	return &dma_mem->shm;
+
+err_free_pages:
+	dma_free_pages(&teedev->dev, page_count * PAGE_SIZE, page, dma_addr,
+		       DMA_BIDIRECTIONAL);
+err_put_teedev:
+	tee_device_put(teedev);
+
+	return ERR_PTR(-ENOMEM);
+}
+EXPORT_SYMBOL_GPL(tee_shm_alloc_dma_mem);
+#else
+struct tee_shm *tee_shm_alloc_dma_mem(struct tee_context *ctx,
+				      size_t page_count)
+{
+	return ERR_PTR(-EINVAL);
+}
+EXPORT_SYMBOL_GPL(tee_shm_alloc_dma_mem);
+#endif
 
 int tee_dyn_shm_alloc_helper(struct tee_shm *shm, size_t size, size_t align,
 			     int (*shm_register)(struct tee_context *ctx,

include/linux/tee_core.h

···
 #define TEE_SHM_POOL		BIT(2)  /* Memory allocated from pool */
 #define TEE_SHM_PRIV		BIT(3)  /* Memory private to TEE driver */
 #define TEE_SHM_DMA_BUF		BIT(4)	/* Memory with dma-buf handle */
+#define TEE_SHM_DMA_MEM		BIT(5)	/* Memory allocated with */
+					/* dma_alloc_pages() */
 
 #define TEE_DEVICE_FLAG_REGISTERED	0x1
 #define TEE_MAX_DEV_NAME_LEN		32
···
  * @returns a pointer to 'struct tee_shm' on success or an ERR_PTR on failure
  */
 struct tee_shm *tee_shm_alloc_priv_buf(struct tee_context *ctx, size_t size);
+
+struct tee_shm *tee_shm_alloc_dma_mem(struct tee_context *ctx,
+				      size_t page_count);
 
 int tee_dyn_shm_alloc_helper(struct tee_shm *shm, size_t size, size_t align,
 			     int (*shm_register)(struct tee_context *ctx,