[PATCH iommufd] iommufd: Make vfio_compat's unmap succeed if the range is already empty

[Jason Gunthorpe]

iommufd returns ENOENT when attempting to unmap a range that is already
empty, while vfio type1 returns success. Fix vfio_compat to match.

Fixes: d624d6652a65 ("iommufd: vfio container FD ioctl compatibility")
Reported-by: Alex Mastro <amas...@fb.com>
Closes: https://lore.kernel.org/r/ap0s5zf9l3swk...@devgpu012.nha5.facebook.com
Signed-off-by: Jason Gunthorpe <j...@nvidia.com>
---
 drivers/iommu/iommufd/io_pagetable.c    | 12 +++---------
 drivers/iommu/iommufd/ioas.c            |  4 ++++
 tools/testing/selftests/iommu/iommufd.c |  2 ++
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/iommufd/io_pagetable.c 
b/drivers/iommu/iommufd/io_pagetable.c
index c0360c450880b8..75d60f2ad90082 100644
--- a/drivers/iommu/iommufd/io_pagetable.c
+++ b/drivers/iommu/iommufd/io_pagetable.c
@@ -707,7 +707,8 @@ static int iopt_unmap_iova_range(struct io_pagetable *iopt, 
unsigned long start,
        struct iopt_area *area;
        unsigned long unmapped_bytes = 0;
        unsigned int tries = 0;
-       int rc = -ENOENT;
+       /* If there are no mapped entries then success */
+       int rc = 0;
 
        /*
         * The domains_rwsem must be held in read mode any time any area->pages
@@ -777,8 +778,6 @@ static int iopt_unmap_iova_range(struct io_pagetable *iopt, 
unsigned long start,
 
                down_write(&iopt->iova_rwsem);
        }
-       if (unmapped_bytes)
-               rc = 0;
 
 out_unlock_iova:
        up_write(&iopt->iova_rwsem);
@@ -815,13 +814,8 @@ int iopt_unmap_iova(struct io_pagetable *iopt, unsigned 
long iova,
 
 int iopt_unmap_all(struct io_pagetable *iopt, unsigned long *unmapped)
 {
-       int rc;
-
-       rc = iopt_unmap_iova_range(iopt, 0, ULONG_MAX, unmapped);
        /* If the IOVAs are empty then unmap all succeeds */
-       if (rc == -ENOENT)
-               return 0;
-       return rc;
+       return iopt_unmap_iova_range(iopt, 0, ULONG_MAX, unmapped);
 }
 
 /* The caller must always free all the nodes in the allowed_iova rb_root. */
diff --git a/drivers/iommu/iommufd/ioas.c b/drivers/iommu/iommufd/ioas.c
index 1542c5fd10a85c..459a7c5169154b 100644
--- a/drivers/iommu/iommufd/ioas.c
+++ b/drivers/iommu/iommufd/ioas.c
@@ -367,6 +367,10 @@ int iommufd_ioas_unmap(struct iommufd_ucmd *ucmd)
                                     &unmapped);
                if (rc)
                        goto out_put;
+               if (!unmapped) {
+                       rc = -ENOENT;
+                       goto out_put;
+               }
        }
 
        cmd->length = unmapped;
diff --git a/tools/testing/selftests/iommu/iommufd.c 
b/tools/testing/selftests/iommu/iommufd.c
index 3eebf5e3b974f4..bb4d33dde3c899 100644
--- a/tools/testing/selftests/iommu/iommufd.c
+++ b/tools/testing/selftests/iommu/iommufd.c
@@ -2638,6 +2638,8 @@ TEST_F(vfio_compat_mock_domain, map)
        ASSERT_EQ(0, ioctl(self->fd, VFIO_IOMMU_MAP_DMA, &map_cmd));
        ASSERT_EQ(0, ioctl(self->fd, VFIO_IOMMU_UNMAP_DMA, &unmap_cmd));
        ASSERT_EQ(BUFFER_SIZE, unmap_cmd.size);
+       /* Unmap of empty is success */
+       ASSERT_EQ(0, ioctl(self->fd, VFIO_IOMMU_UNMAP_DMA, &unmap_cmd));
 
        /* UNMAP_FLAG_ALL requires 0 iova/size */
        ASSERT_EQ(0, ioctl(self->fd, VFIO_IOMMU_MAP_DMA, &map_cmd));

base-commit: b09ed52db1e688eb8205b1939ca1345179ecd515
-- 
2.43.0