[PATCH v3 23/32] vfio: use iova_to_phys_length for efficient unmap

[Guanghui Feng]

Use iommu_iova_to_phys_length() to get PTE page size, allowing
traversal by actual mapping granularity instead of PAGE_SIZE steps.

Signed-off-by: Guanghui Feng <guanghuifeng at linux.alibaba.com>
Acked-by: Shiqiang Zhang <shiyu.zsq at linux.alibaba.com>
Acked-by: Simon Guo <wei.guo.simon at linux.alibaba.com>
---
 drivers/vfio/vfio_iommu_type1.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index c8151ba54de3..115d88d7003e 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -1177,25 +1177,42 @@ static long vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma,
 
 	iommu_iotlb_gather_init(&iotlb_gather);
 	while (pos < dma->size) {
-		size_t unmapped, len;
+		size_t unmapped, len, pgsize;
 		phys_addr_t phys, next;
 		dma_addr_t iova = dma->iova + pos;
 
-		phys = iommu_iova_to_phys(domain->domain, iova);
-		if (WARN_ON(!phys)) {
+		/* Single page table walk returns both phys and PTE size */
+		phys = iommu_iova_to_phys_length(domain->domain, iova,
+						  &pgsize);
+		if (WARN_ON(phys == PHYS_ADDR_MAX)) {
 			pos += PAGE_SIZE;
 			continue;
 		}
+		if (WARN_ON(!pgsize || pgsize < PAGE_SIZE))
+			pgsize = PAGE_SIZE;
 
 		/*
 		 * To optimize for fewer iommu_unmap() calls, each of which
 		 * may require hardware cache flushing, try to find the
 		 * largest contiguous physical memory chunk to unmap.
+		 *
+		 * mapped_length already accounts for contiguous entries
+		 * from iova, then try to join following physically
+		 * contiguous PTEs.
 		 */
-		for (len = PAGE_SIZE; pos + len < dma->size; len += PAGE_SIZE) {
-			next = iommu_iova_to_phys(domain->domain, iova + len);
+		len = min_t(size_t, pgsize, dma->size - pos);
+		for (; pos + len < dma->size; ) {
+			size_t next_pgsize;
+
+			next = iommu_iova_to_phys_length(domain->domain,
+							  iova + len,
+							  &next_pgsize);
 			if (next != phys + len)
 				break;
+			if (WARN_ON(!next_pgsize || next_pgsize < PAGE_SIZE))
+				next_pgsize = PAGE_SIZE;
+			len += min_t(size_t, next_pgsize,
+				     dma->size - pos - len);
 		}
 
 		/*
-- 
2.43.7