Re: [PATCH] KVM: x86/mmu: Guard against collision with KVM-defined PFERR_IMPLICIT_ACCESS

[Huang, Kai]

On Fri, 2023-07-21 at 15:37 -0700, Sean Christopherson wrote:
> Add an assertion in kvm_mmu_page_fault() to ensure the error code provided
> by hardware doesn't conflict with KVM's software-defined IMPLICIT_ACCESS
> flag.  In the unlikely scenario that future hardware starts using bit 48
> for a hardware-defined flag, preserving the bit could result in KVM
> incorrectly interpreting the unknown flag as KVM's IMPLICIT_ACCESS flag.
> 
> WARN so that any such conflict can be surfaced to KVM developers and
> resolved, but otherwise ignore the bit as KVM can't possibly rely on a
> flag it knows nothing about.
> 
> Fixes: 4f4aa80e3b88 ("KVM: X86: Handle implicit supervisor access with SMAP")
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

Acked-by: Kai Huang <kai.huang@xxxxxxxxx>