Re: [PATCH v10 5/9] KVM: Use gfn instead of hva for mmu_notifier_retry

On Tue, Dec 06, 2022 at 03:48:50PM +0000, Fuad Tabba wrote:
...
 > >

quoted

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         */
-       if (unlikely(kvm->mmu_invalidate_in_progress) &&
-           hva >= kvm->mmu_invalidate_range_start &&
-           hva < kvm->mmu_invalidate_range_end)
-               return 1;
+       if (unlikely(kvm->mmu_invalidate_in_progress)) {
+               /*
+                * Dropping mmu_lock after bumping mmu_invalidate_in_progress
+                * but before updating the range is a KVM bug.
+                */
+               if (WARN_ON_ONCE(kvm->mmu_invalidate_range_start == INVALID_GPA ||
+                                kvm->mmu_invalidate_range_end == INVALID_GPA))

INVALID_GPA is an x86-specific define in
arch/x86/include/asm/kvm_host.h, so this doesn't build on other
architectures. The obvious fix is to move it to
include/linux/kvm_host.h.

Hmm, INVALID_GPA is defined as ZERO for x86, not 100% confident this is
correct choice for other architectures, but after search it has not been
used for other architectures, so should be safe to make it common.

As Yu posted a patch:
https://lore.kernel.org/all/20221209023622.274715-1-yu.c.zhang@linux.intel.com/ (local)

There is a GPA_INVALID in include/linux/kvm_types.h and I see ARM has already
been using it so sounds that is exactly what I need.

Chao

With this fixed,

Reviewed-by: Fuad Tabba <redacted>
And the necessary work to port to arm64 (on qemu/arm64):
Tested-by: Fuad Tabba <redacted>

Cheers,
/fuad