Merge tag 'vfio-v6.18-rc1-pt2' of https://github.com/awilliam/linux-vfio

Pull more VFIO updates from Alex Williamson:

 - Optimizations for DMA map and unmap opertions through the type1 vfio
   IOMMU backend.

   This uses various means of batching and hints from the mm structures
   to improve efficiency and therefore performance, resulting in a
   significant speedup for huge page use cases (Li Zhe)

 - Expose supported device migration features through debugfs (Cédric Le
   Goater)

* tag 'vfio-v6.18-rc1-pt2' of https://github.com/awilliam/linux-vfio:
  vfio: Dump migration features under debugfs
  vfio/type1: optimize vfio_unpin_pages_remote()
  vfio/type1: introduce a new member has_rsvd for struct vfio_dma
  vfio/type1: batch vfio_find_vpfn() in function vfio_unpin_pages_remote()
  vfio/type1: optimize vfio_pin_pages_remote()
  mm: introduce num_pages_contiguous()

Documentation/ABI/testing/debugfs-vfio

@@ -23,3 +23,9 @@ Contact:	Longfang Liu <liulongfang@huawei.com>
 Description:	Read the live migration status of the vfio device.
 		The contents of the state file reflects the migration state
 		relative to those defined in the vfio_device_mig_state enum
+
+What:		/sys/kernel/debug/vfio/<device>/migration/features
+Date:		Oct 2025
+KernelVersion:	6.18
+Contact:	Cédric Le Goater <clg@redhat.com>
+Description:	Read the migration features of the vfio device.

drivers/vfio/debugfs.c

@@ -58,6 +58,23 @@ static int vfio_device_state_read(struct seq_file *seq, void *data)
 	return 0;
 }
 
+static int vfio_device_features_read(struct seq_file *seq, void *data)
+{
+	struct device *vf_dev = seq->private;
+	struct vfio_device *vdev = container_of(vf_dev, struct vfio_device, device);
+
+	if (vdev->migration_flags & VFIO_MIGRATION_STOP_COPY)
+		seq_puts(seq, "stop-copy\n");
+	if (vdev->migration_flags & VFIO_MIGRATION_P2P)
+		seq_puts(seq, "p2p\n");
+	if (vdev->migration_flags & VFIO_MIGRATION_PRE_COPY)
+		seq_puts(seq, "pre-copy\n");
+	if (vdev->log_ops)
+		seq_puts(seq, "dirty-tracking\n");
+
+	return 0;
+}
+
 void vfio_device_debugfs_init(struct vfio_device *vdev)
 {
 	struct device *dev = &vdev->device;
@@ -72,6 +89,8 @@ void vfio_device_debugfs_init(struct vfio_device *vdev)
 							vdev->debug_root);
 		debugfs_create_devm_seqfile(dev, "state", vfio_dev_migration,
 					    vfio_device_state_read);
+		debugfs_create_devm_seqfile(dev, "features", vfio_dev_migration,
+					    vfio_device_features_read);
 	}
 }
 

drivers/vfio/vfio_iommu_type1.c

@@ -37,6 +37,7 @@
 #include <linux/vfio.h>
 #include <linux/workqueue.h>
 #include <linux/notifier.h>
+#include <linux/mm_inline.h>
 #include "vfio.h"
 
 #define DRIVER_VERSION  "0.2"
@@ -92,6 +93,7 @@ struct vfio_dma {
 	bool			iommu_mapped;
 	bool			lock_cap;	/* capable(CAP_IPC_LOCK) */
 	bool			vaddr_invalid;
+	bool			has_rsvd;	/* has 1 or more rsvd pfns */
 	struct task_struct	*task;
 	struct rb_root		pfn_list;	/* Ex-user pinned pfn list */
 	unsigned long		*bitmap;
@@ -318,7 +320,13 @@ static void vfio_dma_bitmap_free_all(struct vfio_iommu *iommu)
 /*
  * Helper Functions for host iova-pfn list
  */
-static struct vfio_pfn *vfio_find_vpfn(struct vfio_dma *dma, dma_addr_t iova)
+
+/*
+ * Find the highest vfio_pfn that overlapping the range
+ * [iova_start, iova_end) in rb tree.
+ */
+static struct vfio_pfn *vfio_find_vpfn_range(struct vfio_dma *dma,
+		dma_addr_t iova_start, dma_addr_t iova_end)
 {
 	struct vfio_pfn *vpfn;
 	struct rb_node *node = dma->pfn_list.rb_node;
@@ -326,9 +334,9 @@ static struct vfio_pfn *vfio_find_vpfn(struct vfio_dma *dma, dma_addr_t iova)
 	while (node) {
 		vpfn = rb_entry(node, struct vfio_pfn, node);
 
-		if (iova < vpfn->iova)
+		if (iova_end <= vpfn->iova)
 			node = node->rb_left;
-		else if (iova > vpfn->iova)
+		else if (iova_start > vpfn->iova)
 			node = node->rb_right;
 		else
 			return vpfn;
@@ -336,6 +344,11 @@ static struct vfio_pfn *vfio_find_vpfn(struct vfio_dma *dma, dma_addr_t iova)
 	return NULL;
 }
 
+static inline struct vfio_pfn *vfio_find_vpfn(struct vfio_dma *dma, dma_addr_t iova)
+{
+	return vfio_find_vpfn_range(dma, iova, iova + 1);
+}
+
 static void vfio_link_pfn(struct vfio_dma *dma,
 			  struct vfio_pfn *new)
 {
@@ -614,6 +627,39 @@ done:
 	return ret;
 }
 
+
+static long vpfn_pages(struct vfio_dma *dma,
+		dma_addr_t iova_start, long nr_pages)
+{
+	dma_addr_t iova_end = iova_start + (nr_pages << PAGE_SHIFT);
+	struct vfio_pfn *top = vfio_find_vpfn_range(dma, iova_start, iova_end);
+	long ret = 1;
+	struct vfio_pfn *vpfn;
+	struct rb_node *prev;
+	struct rb_node *next;
+
+	if (likely(!top))
+		return 0;
+
+	prev = next = &top->node;
+
+	while ((prev = rb_prev(prev))) {
+		vpfn = rb_entry(prev, struct vfio_pfn, node);
+		if (vpfn->iova < iova_start)
+			break;
+		ret++;
+	}
+
+	while ((next = rb_next(next))) {
+		vpfn = rb_entry(next, struct vfio_pfn, node);
+		if (vpfn->iova >= iova_end)
+			break;
+		ret++;
+	}
+
+	return ret;
+}
+
 /*
  * Attempt to pin pages.  We really don't want to track all the pfns and
  * the iommu can only map chunks of consecutive pfns anyway, so get the
@@ -687,32 +733,47 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
 		 * and rsvd here, and therefore continues to use the batch.
 		 */
 		while (true) {
+			long nr_pages, acct_pages = 0;
+
 			if (pfn != *pfn_base + pinned ||
 			    rsvd != is_invalid_reserved_pfn(pfn))
 				goto out;
 
+			/*
+			 * Using GUP with the FOLL_LONGTERM in
+			 * vaddr_get_pfns() will not return invalid
+			 * or reserved pages.
+			 */
+			nr_pages = num_pages_contiguous(
+					&batch->pages[batch->offset],
+					batch->size);
+			if (!rsvd) {
+				acct_pages = nr_pages;
+				acct_pages -= vpfn_pages(dma, iova, nr_pages);
+			}
+
 			/*
 			 * Reserved pages aren't counted against the user,
 			 * externally pinned pages are already counted against
 			 * the user.
 			 */
-			if (!rsvd && !vfio_find_vpfn(dma, iova)) {
+			if (acct_pages) {
 				if (!dma->lock_cap &&
-				    mm->locked_vm + lock_acct + 1 > limit) {
+				    mm->locked_vm + lock_acct + acct_pages > limit) {
 					pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n",
 						__func__, limit << PAGE_SHIFT);
 					ret = -ENOMEM;
 					goto unpin_out;
 				}
-				lock_acct++;
+				lock_acct += acct_pages;
 			}
 
-			pinned++;
-			npage--;
-			vaddr += PAGE_SIZE;
-			iova += PAGE_SIZE;
-			batch->offset++;
-			batch->size--;
+			pinned += nr_pages;
+			npage -= nr_pages;
+			vaddr += PAGE_SIZE * nr_pages;
+			iova += PAGE_SIZE * nr_pages;
+			batch->offset += nr_pages;
+			batch->size -= nr_pages;
 
 			if (!batch->size)
 				break;
@@ -722,6 +783,7 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
 	}
 
 out:
+	dma->has_rsvd |= rsvd;
 	ret = vfio_lock_acct(dma, lock_acct, false);
 
 unpin_out:
@@ -738,21 +800,29 @@ unpin_out:
 	return pinned;
 }
 
+static inline void put_valid_unreserved_pfns(unsigned long start_pfn,
+		unsigned long npage, int prot)
+{
+	unpin_user_page_range_dirty_lock(pfn_to_page(start_pfn), npage,
+					 prot & IOMMU_WRITE);
+}
+
 static long vfio_unpin_pages_remote(struct vfio_dma *dma, dma_addr_t iova,
 				    unsigned long pfn, unsigned long npage,
 				    bool do_accounting)
 {
-	long unlocked = 0, locked = 0;
-	long i;
+	long unlocked = 0, locked = vpfn_pages(dma, iova, npage);
 
-	for (i = 0; i < npage; i++, iova += PAGE_SIZE) {
-		if (put_pfn(pfn++, dma->prot)) {
-			unlocked++;
-			if (vfio_find_vpfn(dma, iova))
-				locked++;
-		}
+	if (dma->has_rsvd) {
+		unsigned long i;
+
+		for (i = 0; i < npage; i++)
+			if (put_pfn(pfn++, dma->prot))
+				unlocked++;
+	} else {
+		put_valid_unreserved_pfns(pfn, npage, dma->prot);
+		unlocked = npage;
 	}
-
 	if (do_accounting)
 		vfio_lock_acct(dma, locked - unlocked, true);
 

include/linux/mm.h

@@ -1833,7 +1833,12 @@ static inline unsigned long memdesc_section(memdesc_flags_t mdf)
 {
 	return (mdf.f >> SECTIONS_PGSHIFT) & SECTIONS_MASK;
 }
-#endif
+#else /* !SECTION_IN_PAGE_FLAGS */
+static inline unsigned long memdesc_section(memdesc_flags_t mdf)
+{
+	return 0;
+}
+#endif /* SECTION_IN_PAGE_FLAGS */
 
 /**
  * folio_pfn - Return the Page Frame Number of a folio.

include/linux/mm_inline.h

@@ -617,4 +617,40 @@ static inline bool vma_has_recency(const struct vm_area_struct *vma)
 	return true;
 }
 
+/**
+ * num_pages_contiguous() - determine the number of contiguous pages
+ *			    that represent contiguous PFNs
+ * @pages: an array of page pointers
+ * @nr_pages: length of the array, at least 1
+ *
+ * Determine the number of contiguous pages that represent contiguous PFNs
+ * in @pages, starting from the first page.
+ *
+ * In some kernel configs contiguous PFNs will not have contiguous struct
+ * pages. In these configurations num_pages_contiguous() will return a num
+ * smaller than ideal number. The caller should continue to check for pfn
+ * contiguity after each call to num_pages_contiguous().
+ *
+ * Returns the number of contiguous pages.
+ */
+static inline size_t num_pages_contiguous(struct page **pages, size_t nr_pages)
+{
+	struct page *cur_page = pages[0];
+	unsigned long section = memdesc_section(cur_page->flags);
+	size_t i;
+
+	for (i = 1; i < nr_pages; i++) {
+		if (++cur_page != pages[i])
+			break;
+		/*
+		 * In unproblematic kernel configs, page_to_section() == 0 and
+		 * the whole check will get optimized out.
+		 */
+		if (memdesc_section(cur_page->flags) != section)
+			break;
+	}
+
+	return i;
+}
+
 #endif