On Tue, May 14, 2024, Xiaoyao Li wrote: > On 5/14/2024 1:31 AM, Sean Christopherson wrote: > > On Mon, May 13, 2024, Xiaoyao Li wrote: > > > On 5/7/2024 11:58 PM, Paolo Bonzini wrote: > > > > +#define PFERR_SYNTHETIC_MASK (PFERR_IMPLICIT_ACCESS) > > > > #define PFERR_NESTED_GUEST_PAGE (PFERR_GUEST_PAGE_MASK | \ > > > > PFERR_WRITE_MASK | \ > > > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > > > index c72a2033ca96..5562d693880a 100644 > > > > --- a/arch/x86/kvm/mmu/mmu.c > > > > +++ b/arch/x86/kvm/mmu/mmu.c > > > > @@ -4502,6 +4502,9 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code, > > > > return -EFAULT; > > > > #endif > > > > + /* Ensure the above sanity check also covers KVM-defined flags. */ > > > > > > 1. There is no sanity check above related to KVM-defined flags yet. It has > > > to be after Patch 6. > > > > Ya, it's not just the comment, the entire changelog expects this patch to land > > after patch 6. > > > > > > 2. I somehow cannot parse the comment properly, though I know it's to ensure > > > KVM-defined PFERR_SYNTHETIC_MASK not contain any bit below 32-bits. > > > > Hmm, how about this? > > > > /* > > * Ensure that the above sanity check on hardware error code bits 63:32 > > * also prevents false positives on KVM-defined flags. > > */ > > > > Maybe it's just myself inability, I still cannot interpret it well. > > Can't we put it above the sanity check of error code, and just with a > comment like > > /* > * Ensure KVM-defined flags not occupied any bits below 32-bits, > * that are used by hardware. This is somewhat misleading, as hardware does use bits 63:32 (for #NPF), just not for #PF error codes. And the reason I'm using rather indirect wording is that KVM _could_ define synthetic flags in bits 31:0, there's simply a higher probability of needing to reshuffle bit numbers due to a conflict with a future feature. Is this better? I think it captures what you're looking for, while hopefully also capturing that staying out of bits 31:0 isn't a hard requirement. /* * Restrict KVM-defined flags to bits 63:32 so that it's impossible for * them to conflict with #PF error codes, which are limited to 32 bits. */
