diff mbox series

[v2,1/3] KVM: emulate: Don't inject #GP when emulating RDMPC if CR0.PE=0

Message ID 1633770532-23664-1-git-send-email-wanpengli@tencent.com (mailing list archive)
State New, archived
Headers show
Series [v2,1/3] KVM: emulate: Don't inject #GP when emulating RDMPC if CR0.PE=0 | expand

Commit Message

Wanpeng Li Oct. 9, 2021, 9:08 a.m. UTC 
From: Wanpeng Li <wanpengli@tencent.com>

DM 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 the CR0.PE is 1 checking to rdpmc emulate, though this isn't
strictly necessary since it's impossible for CPL to be >0 if CR0.PE=0.

Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
v1 -> v2:
 * update patch description

 arch/x86/kvm/emulate.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Sean Christopherson Oct. 15, 2021, 11:20 p.m. UTC | #1 
On Sat, Oct 09, 2021, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
> 
> DM mentioned that, RDPMC: 

Heh, missing 'S' in "SDM".

> 
>   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 the CR0.PE is 1 checking to rdpmc emulate, though this isn't
> strictly necessary since it's impossible for CPL to be >0 if CR0.PE=0.
> 
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---

Reviewed-by: Sean Christopherson <seanjc@google.com>
diff mbox series

Patch

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 9a144ca8e146..ab7ec569e8c9 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4213,6 +4213,7 @@  static int check_rdtsc(struct x86_emulate_ctxt *ctxt)
 static int check_rdpmc(struct x86_emulate_ctxt *ctxt)
 {
 	u64 cr4 = ctxt->ops->get_cr(ctxt, 4);
+	u64 cr0 = ctxt->ops->get_cr(ctxt, 0);
 	u64 rcx = reg_read(ctxt, VCPU_REGS_RCX);
 
 	/*
@@ -4222,7 +4223,7 @@  static int check_rdpmc(struct x86_emulate_ctxt *ctxt)
 	if (enable_vmware_backdoor && is_vmware_backdoor_pmc(rcx))
 		return X86EMUL_CONTINUE;
 
-	if ((!(cr4 & X86_CR4_PCE) && ctxt->ops->cpl(ctxt)) ||
+	if ((!(cr4 & X86_CR4_PCE) && ctxt->ops->cpl(ctxt) && (cr0 & X86_CR0_PE)) ||
 	    ctxt->ops->check_pmc(ctxt, rcx))
 		return emulate_gp(ctxt, 0);