diff options
| author | Wanpeng Li | 2021-10-20 03:13:56 -0700 |
|---|---|---|
| committer | Paolo Bonzini | 2021-10-22 05:19:29 -0400 |
| commit | 9ae7f6c9b51e297a7f5c2eb8ff5de42f8402eb71 (patch) | |
| tree | 7aac238a46e4265bec44e4f909aa41ad88ee5307 /arch/x86/kvm | |
| parent | 9dadfc4a6145e163cd18fb4bdea5ca4f44f3c1ad (diff) | |
KVM: emulate: Comment on difference between RDPMC implementation and manual
SDM mentioned that, RDPMC:
IF (((CR4.PCE = 1) or (CPL = 0) or (CR0.PE = 0)) and (ECX indicates a supported counter))
THEN
EAX := counter[31:0];
EDX := ZeroExtend(counter[MSCB:32]);
ELSE (* ECX is not valid or CR4.PCE is 0 and CPL is 1, 2, or 3 and CR0.PE is 1 *)
#GP(0);
FI;
Let's add a comment why CR0.PE isn't tested since it's impossible for CPL to be >0 if
CR0.PE=0.
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1634724836-73721-1-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/emulate.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index c589ac832265..532791ffcbb9 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -4223,6 +4223,11 @@ static int check_rdpmc(struct x86_emulate_ctxt *ctxt) if (enable_vmware_backdoor && is_vmware_backdoor_pmc(rcx)) return X86EMUL_CONTINUE; + /* + * If CR4.PCE is set, the SDM requires CPL=0 or CR0.PE=0. The CR0.PE + * check however is unnecessary because CPL is always 0 outside + * protected mode. + */ if ((!(cr4 & X86_CR4_PCE) && ctxt->ops->cpl(ctxt)) || ctxt->ops->check_pmc(ctxt, rcx)) return emulate_gp(ctxt, 0); |