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[3/3] KVM: x86: Don't re-execute instruction when not passing CR2 value

Message ID 1509891703-9735-4-git-send-email-liran.alon@oracle.com (mailing list archive)
State New, archived
Headers show

Commit Message

Liran Alon Nov. 5, 2017, 2:21 p.m. UTC
From: Liran Alon <liran.alon@ravellosystems.com>

In case of instruction-decode failure or emulation failure,
x86_emulate_instruction() will call reexecute_instruction() which will
attempt to use the cr2 value passed to x86_emulate_instruction().
However, when x86_emulate_instruction() is called from
emulate_instruction(), cr2 is not passed (passed as 0) and therefore
it doesn't make sense to execute reexecute_instruction() logic at all.

Fixes: 51d8b66199e9 ("KVM: cleanup emulate_instruction")

Signed-off-by: Liran Alon <liran.alon@oracle.com>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 arch/x86/include/asm/kvm_host.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Paolo Bonzini Nov. 6, 2017, 9:21 a.m. UTC | #1
On 05/11/2017 15:21, Liran Alon wrote:
> From: Liran Alon <liran.alon@ravellosystems.com>
> 
> In case of instruction-decode failure or emulation failure,
> x86_emulate_instruction() will call reexecute_instruction() which will
> attempt to use the cr2 value passed to x86_emulate_instruction().
> However, when x86_emulate_instruction() is called from
> emulate_instruction(), cr2 is not passed (passed as 0) and therefore
> it doesn't make sense to execute reexecute_instruction() logic at all.
> 
> Fixes: 51d8b66199e9 ("KVM: cleanup emulate_instruction")
> 
> Signed-off-by: Liran Alon <liran.alon@oracle.com>
> Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index c73e493adf07..bc1347949cef 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1156,7 +1156,8 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, unsigned long cr2,
>  static inline int emulate_instruction(struct kvm_vcpu *vcpu,
>  			int emulation_type)
>  {
> -	return x86_emulate_instruction(vcpu, 0, emulation_type, NULL, 0);
> +	return x86_emulate_instruction(vcpu, 0,
> +			emulation_type | EMULTYPE_NO_REEXECUTE, NULL, 0);
>  }
>  
>  void kvm_enable_efer_bits(u64);
> 

You can remove EMULTYPE_NO_REEXECUTE from handle_invalid_guest_state now.

Thanks,

Paolo
Liran Alon Nov. 6, 2017, 10:48 a.m. UTC | #2
On 06/11/17 11:21, Paolo Bonzini wrote:
> On 05/11/2017 15:21, Liran Alon wrote:
>> From: Liran Alon <liran.alon@ravellosystems.com>
>>
>> In case of instruction-decode failure or emulation failure,
>> x86_emulate_instruction() will call reexecute_instruction() which will
>> attempt to use the cr2 value passed to x86_emulate_instruction().
>> However, when x86_emulate_instruction() is called from
>> emulate_instruction(), cr2 is not passed (passed as 0) and therefore
>> it doesn't make sense to execute reexecute_instruction() logic at all.
>>
>> Fixes: 51d8b66199e9 ("KVM: cleanup emulate_instruction")
>>
>> Signed-off-by: Liran Alon <liran.alon@oracle.com>
>> Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
>> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>> ---
>>   arch/x86/include/asm/kvm_host.h | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>> index c73e493adf07..bc1347949cef 100644
>> --- a/arch/x86/include/asm/kvm_host.h
>> +++ b/arch/x86/include/asm/kvm_host.h
>> @@ -1156,7 +1156,8 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, unsigned long cr2,
>>   static inline int emulate_instruction(struct kvm_vcpu *vcpu,
>>   			int emulation_type)
>>   {
>> -	return x86_emulate_instruction(vcpu, 0, emulation_type, NULL, 0);
>> +	return x86_emulate_instruction(vcpu, 0,
>> +			emulation_type | EMULTYPE_NO_REEXECUTE, NULL, 0);
>>   }
>>
>>   void kvm_enable_efer_bits(u64);
>>
>
> You can remove EMULTYPE_NO_REEXECUTE from handle_invalid_guest_state now.
Nice catch. Will remove it in next version of this commit. Thanks.
>
> Thanks,
>
> Paolo
>
diff mbox

Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c73e493adf07..bc1347949cef 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1156,7 +1156,8 @@  int x86_emulate_instruction(struct kvm_vcpu *vcpu, unsigned long cr2,
 static inline int emulate_instruction(struct kvm_vcpu *vcpu,
 			int emulation_type)
 {
-	return x86_emulate_instruction(vcpu, 0, emulation_type, NULL, 0);
+	return x86_emulate_instruction(vcpu, 0,
+			emulation_type | EMULTYPE_NO_REEXECUTE, NULL, 0);
 }
 
 void kvm_enable_efer_bits(u64);