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Change History

In the Linux kernel, the following vulnerability has been resolved:

iommu/vt-d: Disallow dirty tracking if incoherent page walk

Dirty page tracking relies on the IOMMU atomically updating the dirty bit
in the paging-structure entry. For this operation to succeed, the paging-
structure memory must be coherent between the IOMMU and the CPU. In
another word, if the iommu page walk is incoherent, dirty page tracking
doesn't work.

The Intel VT-d specification, Section 3.10 "Snoop Behavior" states:

"Remapping hardware encountering the need to atomically update A/EA/D bits
 in a paging-structure entry that is not snooped will result in a non-
 recoverable fault."

To prevent an IOMMU from being incorrectly configured for dirty page
tracking when it is operating in an incoherent mode, mark SSADS as
supported only when both ecap_slads and ecap_smpwc are supported.

https://git.kernel.org/stable/c/57f55048e564dedd8a4546d018e29d6bbfff0a7e

https://git.kernel.org/stable/c/8d096ce0e87bdc361f0b25d7943543bc53aa0b9e

https://git.kernel.org/stable/c/ebe16d245a00626bb87163862a1b07daf5475a3e