[PATCH 1/7] vfio: iommu_type1: Clear added dirty bit when unwind pin

[Keqian Zhu <zhukeqian1@xxxxxxxxxx>]

Currently we do not clear added dirty bit of bitmap when unwind
pin, so if pin failed at halfway, we set unnecessary dirty bit
in bitmap. Clearing added dirty bit when unwind pin, userspace
will see less dirty page, which can save much time to handle them.

Note that we should distinguish the bits added by pin and the bits
already set before pin, so introduce bitmap_added to record this.

Signed-off-by: Keqian Zhu <zhukeqian1@xxxxxxxxxx>
---
 drivers/vfio/vfio_iommu_type1.c | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 67e827638995..f129d24a6ec3 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -637,7 +637,11 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 	struct vfio_iommu *iommu = iommu_data;
 	struct vfio_group *group;
 	int i, j, ret;
+	unsigned long pgshift = __ffs(iommu->pgsize_bitmap);
 	unsigned long remote_vaddr;
+	unsigned long bitmap_offset;
+	unsigned long *bitmap_added;
+	dma_addr_t iova;
 	struct vfio_dma *dma;
 	bool do_accounting;
 
@@ -650,6 +654,12 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 
 	mutex_lock(&iommu->lock);
 
+	bitmap_added = bitmap_zalloc(npage, GFP_KERNEL);
+	if (!bitmap_added) {
+		ret = -ENOMEM;
+		goto pin_done;
+	}
+
 	/* Fail if notifier list is empty */
 	if (!iommu->notifier.head) {
 		ret = -EINVAL;
@@ -664,7 +674,6 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 	do_accounting = !IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu);
 
 	for (i = 0; i < npage; i++) {
-		dma_addr_t iova;
 		struct vfio_pfn *vpfn;
 
 		iova = user_pfn[i] << PAGE_SHIFT;
@@ -699,14 +708,10 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 		}
 
 		if (iommu->dirty_page_tracking) {
-			unsigned long pgshift = __ffs(iommu->pgsize_bitmap);
-
-			/*
-			 * Bitmap populated with the smallest supported page
-			 * size
-			 */
-			bitmap_set(dma->bitmap,
-				   (iova - dma->iova) >> pgshift, 1);
+			/* Populated with the smallest supported page size */
+			bitmap_offset = (iova - dma->iova) >> pgshift;
+			if (!test_and_set_bit(bitmap_offset, dma->bitmap))
+				set_bit(i, bitmap_added);
 		}
 	}
 	ret = i;
@@ -722,14 +727,20 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 pin_unwind:
 	phys_pfn[i] = 0;
 	for (j = 0; j < i; j++) {
-		dma_addr_t iova;
-
 		iova = user_pfn[j] << PAGE_SHIFT;
 		dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
 		vfio_unpin_page_external(dma, iova, do_accounting);
 		phys_pfn[j] = 0;
+
+		if (test_bit(j, bitmap_added)) {
+			bitmap_offset = (iova - dma->iova) >> pgshift;
+			clear_bit(bitmap_offset, dma->bitmap);
+		}
 	}
 pin_done:
+	if (bitmap_added)
+		bitmap_free(bitmap_added);
+
 	mutex_unlock(&iommu->lock);
 	return ret;
 }
-- 
2.23.0