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Previously, commit <304b3bde24b5> ("iommu/vt-d: Remove caching mode >>> check before device TLB flush") removed this redundant check in the >>> domain unmap path. >>> >>> Checking the caching mode before flushing the device TLB after a pasid >>> table entry is updated is unnecessary and can lead to inconsistent >>> behavior. >>> >>> Extends this consistency by removing the caching mode check in the pasid >>> table update path. >> >> I'm wondering if a fix tag is needed here. Before this patch, the guest >> kernel does not issue device TLB invalidation. This may be a problem for >> the emulated devices that support ATS capability. The cache in device >> side would be stale. Although some vIOMMU like QEMU virtual VT-d would >> notify the emulated devices to flush their cache when handling the unmap >> event. [1]. But this is not required by VT-d spec. So it's possible that >> other vIOMMU may not do it. So this patch appears to fix an issue, so a fix >> tag may be necessary. How about your thought? > > It depends on whether this solves any real or potential issues. What about the rule for it? A real issue should already been reported or identified to happen even no one complained yet due to no related tests. :) -- Regards, Yi Liu