On Mon, May 13, 2024, Xiaoyao Li wrote: > On 5/7/2024 11:58 PM, Paolo Bonzini wrote: > > From: Sean Christopherson <seanjc@xxxxxxxxxx> > > > > Move the sanity check that hardware never sets bits that collide with KVM- > > define synthetic bits from kvm_mmu_page_fault() to npf_interception(), > > i.e. make the sanity check #NPF specific. The legacy #PF path already > > WARNs if _any_ of bits 63:32 are set, and the error code that comes from > > VMX's EPT Violatation and Misconfig is 100% synthesized (KVM morphs VMX's > > EXIT_QUALIFICATION into error code flags). > > > > Add a compile-time assert in the legacy #PF handler to make sure that KVM- > > define flags are covered by its existing sanity check on the upper bits. > > > > Opportunistically add a description of PFERR_IMPLICIT_ACCESS, since we > > are removing the comment that defined it. > > > > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> > > Reviewed-by: Kai Huang <kai.huang@xxxxxxxxx> > > Reviewed-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx> > > Message-ID: <20240228024147.41573-8-seanjc@xxxxxxxxxx> > > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > > --- > > arch/x86/include/asm/kvm_host.h | 6 ++++++ > > arch/x86/kvm/mmu/mmu.c | 14 +++----------- > > arch/x86/kvm/svm/svm.c | 9 +++++++++ > > 3 files changed, 18 insertions(+), 11 deletions(-) > > > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > > index 58bbcf76ad1e..12e727301262 100644 > > --- a/arch/x86/include/asm/kvm_host.h > > +++ b/arch/x86/include/asm/kvm_host.h > > @@ -267,7 +267,13 @@ enum x86_intercept_stage; > > #define PFERR_GUEST_ENC_MASK BIT_ULL(34) > > #define PFERR_GUEST_SIZEM_MASK BIT_ULL(35) > > #define PFERR_GUEST_VMPL_MASK BIT_ULL(36) > > + > > +/* > > + * IMPLICIT_ACCESS is a KVM-defined flag used to correctly perform SMAP checks > > + * when emulating instructions that triggers implicit access. > > + */ > > #define PFERR_IMPLICIT_ACCESS BIT_ULL(48) > > +#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. */
