Messages in this thread | | | Date | Fri, 1 Mar 2024 11:19:37 +1300 | Subject | Re: [PATCH 07/16] KVM: x86: Move synthetic PFERR_* sanity checks to SVM's #NPF handler | From | "Huang, Kai" <> |
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On 28/02/2024 3:41 pm, Sean Christopherson wrote: > 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. > > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/x86/kvm/mmu/mmu.c | 12 +++--------- > arch/x86/kvm/svm/svm.c | 9 +++++++++ > 2 files changed, 12 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 5d892bd59c97..bd342ebd0809 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -4561,6 +4561,9 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code, > if (WARN_ON_ONCE(error_code >> 32)) > error_code = lower_32_bits(error_code); > > + /* Ensure the above sanity check also covers KVM-defined flags. */ > + BUILD_BUG_ON(lower_32_bits(PFERR_SYNTHETIC_MASK)); > +
Could you explain why adding this BUILD_BUG_ON() here, but not ...
> vcpu->arch.l1tf_flush_l1d = true; > if (!flags) { > trace_kvm_page_fault(vcpu, fault_address, error_code); > @@ -5845,15 +5848,6 @@ int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 err > int r, emulation_type = EMULTYPE_PF; > bool direct = vcpu->arch.mmu->root_role.direct; > > - /* > - * WARN if hardware generates a fault with an error code that collides > - * with KVM-defined sythentic flags. Clear the flags and continue on, > - * i.e. don't terminate the VM, as KVM can't possibly be relying on a > - * flag that KVM doesn't know about. > - */ > - if (WARN_ON_ONCE(error_code & PFERR_SYNTHETIC_MASK)) > - error_code &= ~PFERR_SYNTHETIC_MASK; > - > if (WARN_ON_ONCE(!VALID_PAGE(vcpu->arch.mmu->root.hpa))) > return RET_PF_RETRY; > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index e90b429c84f1..199c4dd8d214 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -2055,6 +2055,15 @@ static int npf_interception(struct kvm_vcpu *vcpu) > u64 fault_address = svm->vmcb->control.exit_info_2; > u64 error_code = svm->vmcb->control.exit_info_1; > > + /* > + * WARN if hardware generates a fault with an error code that collides > + * with KVM-defined sythentic flags. Clear the flags and continue on, > + * i.e. don't terminate the VM, as KVM can't possibly be relying on a > + * flag that KVM doesn't know about. > + */ > + if (WARN_ON_ONCE(error_code & PFERR_SYNTHETIC_MASK)) > + error_code &= ~PFERR_SYNTHETIC_MASK; > + > trace_kvm_page_fault(vcpu, fault_address, error_code); > return kvm_mmu_page_fault(vcpu, fault_address, error_code, > static_cpu_has(X86_FEATURE_DECODEASSISTS) ?
.. in npf_interception() or some common place like in kvm_mmu_page_fault()?
Otherwise,
Reviewed-by: Kai Huang <kai.huang@intel.com>
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