Re: [PATCH 3/4] KVM: x86/mmu: Make sure pfn is not changed for spurious fault

[Sean Christopherson]

On Fri, Feb 07, 2025, Yan Zhao wrote:
> Make sure pfn is not changed for a spurious fault by warning in the TDP
> MMU. For shadow path, only treat a prefetch fault as spurious when pfn is
> not changed, since the rmap removal and add are required when pfn is
> changed.

I like sanity checks, but I don't like special casing "prefetch" faults like this.
KVM should _never_ change the PFN of a shadow-present SPTE.  The TDP MMU already
BUG()s on this, and mmu_spte_update() WARNs on the transition.