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SubjectRE: [RFC PATCH v6 037/104] KVM: x86/mmu: Allow non-zero value for non-present SPTE
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> > In addition to the suggestions above, I'd suggest breaking this patch
> > up, since it is doing multiple things:
> >
> > 1. Patch initialize shadow page tables to EMPTY_SPTE (0) and
> > replace TDP MMU hard-coded 0 with EMPTY_SPTE.
> > 2. Patch to change FNAME(sync_page) to not assume EMPTY_SPTE is 0.
> > 3. Patch to set bit 63 in EMPTY_SPTE.
> > 4. Patch to set bit 63 in REMOVED_SPTE.

I think 1/2 can be separate patches, but 3/4 should be done together.

Patch 3 alone is broken as when TDP MMU zaps SPTE and replaces it with REMOVED_SPTE, it loses bit 63. This is not what we want. We always want bit 63 set if it is supposed to be set to a non-present SPTE.

But I also don't see splitting to 3 patches is absolutely worth to do as doing above in one patch is also fine to me.

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