On Fri, 22 Sep 2023 22:32:29 +0000, Oliver Upton wrote:
> It is possible for multiple vCPUs to fault on the same IPA and attempt
> to resolve the fault. One of the page table walks will actually update
> the PTE and the rest will return -EAGAIN per our race detection scheme.
> KVM elides the TLB invalidation on the racing threads as the return
> value is nonzero.
>
> Before commit a12ab1378a88 ("KVM: arm64: Use local TLBI on permission
> relaxation") KVM always used broadcast TLB invalidations when handling
> permission faults, which had the convenient property of making the
> stage-2 updates visible to all CPUs in the system. However now we do a
> local invalidation, and TLBI elision leads to vCPUs getting stuck in a
> permission fault loop. Remember that the architecture permits the TLB to
> cache translations that precipitate a permission fault.
>
> [...]
Applied to kvmarm/next, with the fixes and stable tag dropped.
[1/1] KVM: arm64: Always invalidate TLB for stage-2 permission faults
https://git.kernel.org/kvmarm/kvmarm/c/5a6e594fc607
--
Best,
Oliver
