diff options
| author | Sean Christopherson <seanjc@google.com> | 2023-07-21 15:37:11 -0700 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2023-08-31 13:48:39 -0400 |
| commit | d09f711233a43869725abc44102117d2a8fae6fe (patch) | |
| tree | 56a766abccd850b0769f4beba691170cdf4fd47a /arch/x86/kvm/mmu/mmu.c | |
| parent | 91303f800e76517d1e96d47dec290c5d5dbf1230 (diff) | |
| download | lwn-d09f711233a43869725abc44102117d2a8fae6fe.tar.gz lwn-d09f711233a43869725abc44102117d2a8fae6fe.zip | |
KVM: x86/mmu: Guard against collision with KVM-defined PFERR_IMPLICIT_ACCESS
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")
Acked-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20230721223711.2334426-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/mmu/mmu.c')
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 276157f8496c..862604b6e6a3 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -5724,6 +5724,17 @@ 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; + /* + * IMPLICIT_ACCESS is a KVM-defined flag used to correctly perform SMAP + * checks when emulating instructions that triggers implicit access. + * WARN if hardware generates a fault with an error code that collides + * with the KVM-defined value. Clear the flag 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_IMPLICIT_ACCESS)) + error_code &= ~PFERR_IMPLICIT_ACCESS; + if (WARN_ON(!VALID_PAGE(vcpu->arch.mmu->root.hpa))) return RET_PF_RETRY; |