(CC Jason Wang) > From: Jason Gunthorpe > Sent: Thursday, April 7, 2022 11:24 PM > > While the comment was correct that this flag was intended to convey the > block no-snoop support in the IOMMU, it has become widely implemented > and > used to mean the IOMMU supports IOMMU_CACHE as a map flag. Only the > Intel > driver was different. > > Now that the Intel driver is using enforce_cache_coherency() update the > comment to make it clear that IOMMU_CAP_CACHE_COHERENCY is only > about > IOMMU_CACHE. Fix the Intel driver to return true since IOMMU_CACHE > always > works. > > The two places that test this flag, usnic and vdpa, are both assigning > userspace pages to a driver controlled iommu_domain and require > IOMMU_CACHE behavior as they offer no way for userspace to synchronize > caches. > > Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx> btw the comment about vsnic and vdpa matches my thought. But a recent change in Qemu [1] possibly wants confirmation from Jason Wang. [1] https://lore.kernel.org/all/20220304133556.233983-20-mst@xxxxxxxxxx/ Thanks Kevin
