Messages in this thread | | | Date | Wed, 20 Oct 2021 12:45:14 +0200 | Subject | Re: [PATCH v5] KVM: emulate: Don't inject #GP when emulating RDMPC if CR0.PE=0 | From | Paolo Bonzini <> |
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On 20/10/21 12:13, Wanpeng Li wrote: > From: Wanpeng Li <wanpengli@tencent.com> > > 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. > > Reviewed-by: Sean Christopherson <seanjc@google.com> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > --- > v4 -> v5: > * just comments > v3 -> v4: > * add comments instead of pseudocode > v2 -> v3: > * add the missing 'S' > v1 -> v2: > * update patch description > > arch/x86/kvm/emulate.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 9a144ca8e146..c289809beea3 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -4222,6 +4222,9 @@ static int check_rdpmc(struct x86_emulate_ctxt *ctxt) > if (enable_vmware_backdoor && is_vmware_backdoor_pmc(rcx)) > return X86EMUL_CONTINUE; > > + /* > + * It's impossible for CPL to be >0 if CR0.PE=0. > + */ > if ((!(cr4 & X86_CR4_PCE) && ctxt->ops->cpl(ctxt)) || > ctxt->ops->check_pmc(ctxt, rcx)) > return emulate_gp(ctxt, 0); >
Queued, thanks (with a slightly more verbose comment).
Paolo
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