KVM: x86: Get RIP from vCPU state when storing it to last_retry_eip

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.

No functional change intended, 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).

Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20240831001538.336683-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5d4bcb9..760d455 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8971,7 +8971,7 @@ 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;
 }