xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE

My recent Xen patch series introduces a new HYPERVISOR_memory_op to
support direct priv-mapping of certain guest resources (such as ioreq
pages, used by emulators) by a tools domain, rather than having to access
such resources via the guest P2M.

This patch adds the necessary infrastructure to the privcmd driver and
Xen MMU code to support direct resource mapping.

NOTE: The adjustment in the MMU code is partially cosmetic. Xen will now
allow a PV tools domain to map guest pages either by GFN or MFN, thus
the term 'mfn' has been swapped for 'pfn' in the lower layers of the
remap code.

Signed-off-by: Paul Durrant <[e-mail]>
Reviewed-by: Boris Ostrovsky <[e-mail]>
Signed-off-by: Juergen Gross <[e-mail]>

arch/arm/xen/enlighten.c

···
 }
 EXPORT_SYMBOL_GPL(xen_unmap_domain_gfn_range);
 
+/* Not used by XENFEAT_auto_translated guests. */
+int xen_remap_domain_mfn_array(struct vm_area_struct *vma,
+			       unsigned long addr,
+			       xen_pfn_t *mfn, int nr,
+			       int *err_ptr, pgprot_t prot,
+			       unsigned int domid, struct page **pages)
+{
+	return -ENOSYS;
+}
+EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_array);
+
 static void xen_read_wallclock(struct timespec64 *ts)
 {
 	u32 version;

arch/x86/xen/mmu.c

···
 #define REMAP_BATCH_SIZE 16
 
 struct remap_data {
-	xen_pfn_t *mfn;
+	xen_pfn_t *pfn;
 	bool contiguous;
+	bool no_translate;
 	pgprot_t prot;
 	struct mmu_update *mmu_update;
 };
 
-static int remap_area_mfn_pte_fn(pte_t *ptep, pgtable_t token,
+static int remap_area_pfn_pte_fn(pte_t *ptep, pgtable_t token,
 				 unsigned long addr, void *data)
 {
 	struct remap_data *rmd = data;
-	pte_t pte = pte_mkspecial(mfn_pte(*rmd->mfn, rmd->prot));
+	pte_t pte = pte_mkspecial(mfn_pte(*rmd->pfn, rmd->prot));
 
-	/* If we have a contiguous range, just update the mfn itself,
-	   else update pointer to be "next mfn". */
+	/*
+	 * If we have a contiguous range, just update the pfn itself,
+	 * else update pointer to be "next pfn".
+	 */
 	if (rmd->contiguous)
-		(*rmd->mfn)++;
+		(*rmd->pfn)++;
 	else
-		rmd->mfn++;
+		rmd->pfn++;
 
-	rmd->mmu_update->ptr = virt_to_machine(ptep).maddr | MMU_NORMAL_PT_UPDATE;
+	rmd->mmu_update->ptr = virt_to_machine(ptep).maddr;
+	rmd->mmu_update->ptr |= rmd->no_translate ?
+		MMU_PT_UPDATE_NO_TRANSLATE :
+		MMU_NORMAL_PT_UPDATE;
 	rmd->mmu_update->val = pte_val_ma(pte);
 	rmd->mmu_update++;
 
 	return 0;
 }
 
-static int do_remap_gfn(struct vm_area_struct *vma,
+static int do_remap_pfn(struct vm_area_struct *vma,
 			unsigned long addr,
-			xen_pfn_t *gfn, int nr,
+			xen_pfn_t *pfn, int nr,
 			int *err_ptr, pgprot_t prot,
-			unsigned domid,
+			unsigned int domid,
+			bool no_translate,
 			struct page **pages)
 {
 	int err = 0;
···
 
 	BUG_ON(!((vma->vm_flags & (VM_PFNMAP | VM_IO)) == (VM_PFNMAP | VM_IO)));
 
-	rmd.mfn = gfn;
+	rmd.pfn = pfn;
 	rmd.prot = prot;
-	/* We use the err_ptr to indicate if there we are doing a contiguous
-	 * mapping or a discontigious mapping. */
+	/*
+	 * We use the err_ptr to indicate if there we are doing a contiguous
+	 * mapping or a discontigious mapping.
+	 */
 	rmd.contiguous = !err_ptr;
+	rmd.no_translate = no_translate;
 
 	while (nr) {
 		int index = 0;
···
 
 		rmd.mmu_update = mmu_update;
 		err = apply_to_page_range(vma->vm_mm, addr, range,
-					  remap_area_mfn_pte_fn, &rmd);
+					  remap_area_pfn_pte_fn, &rmd);
 		if (err)
 			goto out;
 
···
 	if (xen_feature(XENFEAT_auto_translated_physmap))
 		return -EOPNOTSUPP;
 
-	return do_remap_gfn(vma, addr, &gfn, nr, NULL, prot, domid, pages);
+	return do_remap_pfn(vma, addr, &gfn, nr, NULL, prot, domid, false,
+			    pages);
 }
 EXPORT_SYMBOL_GPL(xen_remap_domain_gfn_range);
 
···
 	 * cause of "wrong memory was mapped in".
 	 */
 	BUG_ON(err_ptr == NULL);
-	return do_remap_gfn(vma, addr, gfn, nr, err_ptr, prot, domid, pages);
+	return do_remap_pfn(vma, addr, gfn, nr, err_ptr, prot, domid,
+			    false, pages);
 }
 EXPORT_SYMBOL_GPL(xen_remap_domain_gfn_array);
+
+int xen_remap_domain_mfn_array(struct vm_area_struct *vma,
+			       unsigned long addr,
+			       xen_pfn_t *mfn, int nr,
+			       int *err_ptr, pgprot_t prot,
+			       unsigned int domid, struct page **pages)
+{
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		return -EOPNOTSUPP;
+
+	return do_remap_pfn(vma, addr, mfn, nr, err_ptr, prot, domid,
+			    true, pages);
+}
+EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_array);
 
 /* Returns: 0 success */
 int xen_unmap_domain_gfn_range(struct vm_area_struct *vma,

drivers/xen/privcmd.c

···
 #include <xen/xen.h>
 #include <xen/privcmd.h>
 #include <xen/interface/xen.h>
+#include <xen/interface/memory.h>
 #include <xen/interface/hvm/dm_op.h>
 #include <xen/features.h>
 #include <xen/page.h>
···
 	return 0;
 }
 
+struct remap_pfn {
+	struct mm_struct *mm;
+	struct page **pages;
+	pgprot_t prot;
+	unsigned long i;
+};
+
+static int remap_pfn_fn(pte_t *ptep, pgtable_t token, unsigned long addr,
+			void *data)
+{
+	struct remap_pfn *r = data;
+	struct page *page = r->pages[r->i];
+	pte_t pte = pte_mkspecial(pfn_pte(page_to_pfn(page), r->prot));
+
+	set_pte_at(r->mm, addr, ptep, pte);
+	r->i++;
+
+	return 0;
+}
+
+static long privcmd_ioctl_mmap_resource(struct file *file, void __user *udata)
+{
+	struct privcmd_data *data = file->private_data;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	struct privcmd_mmap_resource kdata;
+	xen_pfn_t *pfns = NULL;
+	struct xen_mem_acquire_resource xdata;
+	int rc;
+
+	if (copy_from_user(&kdata, udata, sizeof(kdata)))
+		return -EFAULT;
+
+	/* If restriction is in place, check the domid matches */
+	if (data->domid != DOMID_INVALID && data->domid != kdata.dom)
+		return -EPERM;
+
+	down_write(&mm->mmap_sem);
+
+	vma = find_vma(mm, kdata.addr);
+	if (!vma || vma->vm_ops != &privcmd_vm_ops) {
+		rc = -EINVAL;
+		goto out;
+	}
+
+	pfns = kcalloc(kdata.num, sizeof(*pfns), GFP_KERNEL);
+	if (!pfns) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	if (xen_feature(XENFEAT_auto_translated_physmap)) {
+		unsigned int nr = DIV_ROUND_UP(kdata.num, XEN_PFN_PER_PAGE);
+		struct page **pages;
+		unsigned int i;
+
+		rc = alloc_empty_pages(vma, nr);
+		if (rc < 0)
+			goto out;
+
+		pages = vma->vm_private_data;
+		for (i = 0; i < kdata.num; i++) {
+			xen_pfn_t pfn =
+				page_to_xen_pfn(pages[i / XEN_PFN_PER_PAGE]);
+
+			pfns[i] = pfn + (i % XEN_PFN_PER_PAGE);
+		}
+	} else
+		vma->vm_private_data = PRIV_VMA_LOCKED;
+
+	memset(&xdata, 0, sizeof(xdata));
+	xdata.domid = kdata.dom;
+	xdata.type = kdata.type;
+	xdata.id = kdata.id;
+	xdata.frame = kdata.idx;
+	xdata.nr_frames = kdata.num;
+	set_xen_guest_handle(xdata.frame_list, pfns);
+
+	xen_preemptible_hcall_begin();
+	rc = HYPERVISOR_memory_op(XENMEM_acquire_resource, &xdata);
+	xen_preemptible_hcall_end();
+
+	if (rc)
+		goto out;
+
+	if (xen_feature(XENFEAT_auto_translated_physmap)) {
+		struct remap_pfn r = {
+			.mm = vma->vm_mm,
+			.pages = vma->vm_private_data,
+			.prot = vma->vm_page_prot,
+		};
+
+		rc = apply_to_page_range(r.mm, kdata.addr,
+					 kdata.num << PAGE_SHIFT,
+					 remap_pfn_fn, &r);
+	} else {
+		unsigned int domid =
+			(xdata.flags & XENMEM_rsrc_acq_caller_owned) ?
+			DOMID_SELF : kdata.dom;
+		int num;
+
+		num = xen_remap_domain_mfn_array(vma,
+						 kdata.addr & PAGE_MASK,
+						 pfns, kdata.num, (int *)pfns,
+						 vma->vm_page_prot,
+						 domid,
+						 vma->vm_private_data);
+		if (num < 0)
+			rc = num;
+		else if (num != kdata.num) {
+			unsigned int i;
+
+			for (i = 0; i < num; i++) {
+				rc = pfns[i];
+				if (rc < 0)
+					break;
+			}
+		} else
+			rc = 0;
+	}
+
+out:
+	up_write(&mm->mmap_sem);
+	kfree(pfns);
+
+	return rc;
+}
+
 static long privcmd_ioctl(struct file *file,
 			  unsigned int cmd, unsigned long data)
 {
···
 
 	case IOCTL_PRIVCMD_RESTRICT:
 		ret = privcmd_ioctl_restrict(file, udata);
+		break;
+
+	case IOCTL_PRIVCMD_MMAP_RESOURCE:
+		ret = privcmd_ioctl_mmap_resource(file, udata);
 		break;
 
 	default:

include/uapi/xen/privcmd.h

···
 	const struct privcmd_dm_op_buf __user *ubufs;
 };
 
+struct privcmd_mmap_resource {
+	domid_t dom;
+	__u32 type;
+	__u32 id;
+	__u32 idx;
+	__u64 num;
+	__u64 addr;
+};
+
 /*
  * @cmd: IOCTL_PRIVCMD_HYPERCALL
  * @arg: &privcmd_hypercall_t
···
 	_IOC(_IOC_NONE, 'P', 5, sizeof(struct privcmd_dm_op))
 #define IOCTL_PRIVCMD_RESTRICT					\
 	_IOC(_IOC_NONE, 'P', 6, sizeof(domid_t))
+#define IOCTL_PRIVCMD_MMAP_RESOURCE				\
+	_IOC(_IOC_NONE, 'P', 7, sizeof(struct privcmd_mmap_resource))
 
 #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */

include/xen/interface/memory.h

···
 };
 DEFINE_GUEST_HANDLE_STRUCT(xen_remove_from_physmap);
 
+/*
+ * Get the pages for a particular guest resource, so that they can be
+ * mapped directly by a tools domain.
+ */
+#define XENMEM_acquire_resource 28
+struct xen_mem_acquire_resource {
+    /* IN - The domain whose resource is to be mapped */
+    domid_t domid;
+    /* IN - the type of resource */
+    uint16_t type;
+
+#define XENMEM_resource_ioreq_server 0
+#define XENMEM_resource_grant_table 1
+
+    /*
+     * IN - a type-specific resource identifier, which must be zero
+     *      unless stated otherwise.
+     *
+     * type == XENMEM_resource_ioreq_server -> id == ioreq server id
+     * type == XENMEM_resource_grant_table -> id defined below
+     */
+    uint32_t id;
+
+#define XENMEM_resource_grant_table_id_shared 0
+#define XENMEM_resource_grant_table_id_status 1
+
+    /* IN/OUT - As an IN parameter number of frames of the resource
+     *          to be mapped. However, if the specified value is 0 and
+     *          frame_list is NULL then this field will be set to the
+     *          maximum value supported by the implementation on return.
+     */
+    uint32_t nr_frames;
+    /*
+     * OUT - Must be zero on entry. On return this may contain a bitwise
+     *       OR of the following values.
+     */
+    uint32_t flags;
+
+    /* The resource pages have been assigned to the calling domain */
+#define _XENMEM_rsrc_acq_caller_owned 0
+#define XENMEM_rsrc_acq_caller_owned (1u << _XENMEM_rsrc_acq_caller_owned)
+
+    /*
+     * IN - the index of the initial frame to be mapped. This parameter
+     *      is ignored if nr_frames is 0.
+     */
+    uint64_t frame;
+
+#define XENMEM_resource_ioreq_server_frame_bufioreq 0
+#define XENMEM_resource_ioreq_server_frame_ioreq(n) (1 + (n))
+
+    /*
+     * IN/OUT - If the tools domain is PV then, upon return, frame_list
+     *          will be populated with the MFNs of the resource.
+     *          If the tools domain is HVM then it is expected that, on
+     *          entry, frame_list will be populated with a list of GFNs
+     *          that will be mapped to the MFNs of the resource.
+     *          If -EIO is returned then the frame_list has only been
+     *          partially mapped and it is up to the caller to unmap all
+     *          the GFNs.
+     *          This parameter may be NULL if nr_frames is 0.
+     */
+    GUEST_HANDLE(xen_pfn_t) frame_list;
+};
+DEFINE_GUEST_HANDLE_STRUCT(xen_mem_acquire_resource);
+
 #endif /* __XEN_PUBLIC_MEMORY_H__ */

include/xen/interface/xen.h

···
  *
  * PAT (bit 7 on) --> PWT (bit 3 on) and clear bit 7.
  */
-#define MMU_NORMAL_PT_UPDATE      0 /* checked '*ptr = val'. ptr is MA.       */
-#define MMU_MACHPHYS_UPDATE       1 /* ptr = MA of frame to modify entry for  */
-#define MMU_PT_UPDATE_PRESERVE_AD 2 /* atomically: *ptr = val | (*ptr&(A|D)) */
+#define MMU_NORMAL_PT_UPDATE       0 /* checked '*ptr = val'. ptr is MA.      */
+#define MMU_MACHPHYS_UPDATE        1 /* ptr = MA of frame to modify entry for */
+#define MMU_PT_UPDATE_PRESERVE_AD  2 /* atomically: *ptr = val | (*ptr&(A|D)) */
+#define MMU_PT_UPDATE_NO_TRANSLATE 3 /* checked '*ptr = val'. ptr is MA.      */
 
 /*
  * MMU EXTENDED OPERATIONS

include/xen/xen-ops.h

···
 struct vm_area_struct;
 
 /*
- * xen_remap_domain_gfn_array() - map an array of foreign frames
+ * xen_remap_domain_gfn_array() - map an array of foreign frames by gfn
  * @vma:     VMA to map the pages into
  * @addr:    Address at which to map the pages
  * @gfn:     Array of GFNs to map
···
 			       int *err_ptr, pgprot_t prot,
 			       unsigned domid,
 			       struct page **pages);
+
+/*
+ * xen_remap_domain_mfn_array() - map an array of foreign frames by mfn
+ * @vma:     VMA to map the pages into
+ * @addr:    Address at which to map the pages
+ * @mfn:     Array of MFNs to map
+ * @nr:      Number entries in the MFN array
+ * @err_ptr: Returns per-MFN error status.
+ * @prot:    page protection mask
+ * @domid:   Domain owning the pages
+ * @pages:   Array of pages if this domain has an auto-translated physmap
+ *
+ * @mfn and @err_ptr may point to the same buffer, the MFNs will be
+ * overwritten by the error codes after they are mapped.
+ *
+ * Returns the number of successfully mapped frames, or a -ve error
+ * code.
+ */
+int xen_remap_domain_mfn_array(struct vm_area_struct *vma,
+			       unsigned long addr, xen_pfn_t *mfn, int nr,
+			       int *err_ptr, pgprot_t prot,
+			       unsigned int domid, struct page **pages);
 
 /* xen_remap_domain_gfn_range() - map a range of foreign frames
  * @vma:     VMA to map the pages into