On 8/9/24 21:03, Sean Christopherson wrote:
> Read RIP from vCPU state instead of pulling it from the emulation context
> when filling last_retry_eip, which is part of the anti-infinite-loop
> protection used when unprotecting and retrying instructions that hit a
> write-protected gfn.
>
> This will allow reusing the anti-infinite-loop protection in flows that
> never make it into the emulator.
>
> This is a glorified nop as ctxt->eip is set to kvm_rip_read() in
> init_emulate_ctxt(), and EMULTYPE_PF emulation is mutually exclusive with
> EMULTYPE_NO_DECODE and EMULTYPE_SKIP, i.e. always goes through
> x86_decode_emulated_instruction() and hasn't advanced ctxt->eip (yet).
This is as much a nit as it can be, but "glorified nop" would be
interpreted more as "the assignment is not needed at all", or something
similarly wrong. Just "This has no functional change because..." will do.
Paolo
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/x86.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 2072cceac68f..372ed3842732 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8973,7 +8973,7 @@ static bool retry_instruction(struct x86_emulate_ctxt *ctxt,
> if (!kvm_mmu_unprotect_page(vcpu->kvm, gpa_to_gfn(gpa)))
> return false;
>
> - vcpu->arch.last_retry_eip = ctxt->eip;
> + vcpu->arch.last_retry_eip = kvm_rip_read(vcpu);
> vcpu->arch.last_retry_addr = cr2_or_gpa;
> return true;
> }