On 5/14/2024 11:32 PM, Sean Christopherson wrote:
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.
yeah, it looks better!
/*
* 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.
*/
