diff mbox series

[v2,9/9] KVM: x86: remove exit_int_info warning in svm_handle_exit

Message ID 20221103141351.50662-10-mlevitsk@redhat.com
State New
Headers
Series nSVM: Security and correctness fixes |

Commit Message

Maxim Levitsky Nov. 3, 2022, 2:13 p.m. UTC 
  It is valid to receive external interrupt and have broken IDT entry,
which will lead to #GP with exit_int_into that will contain the index of
the IDT entry (e.g any value).

Other exceptions can happen as well, like #NP or #SS
(if stack switch fails).

Thus this warning can be user triggred and has very little value.

Cc: stable@vger.kernel.org
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/svm/svm.c | 9 ---------
 1 file changed, 9 deletions(-)

Comments

Liam Merwick Nov. 6, 2022, 3:53 p.m. UTC | #1 
On 03/11/2022 14:13, Maxim Levitsky wrote:
> It is valid to receive external interrupt and have broken IDT entry,
> which will lead to #GP with exit_int_into that will contain the index of
> the IDT entry (e.g any value).
> 
> Other exceptions can happen as well, like #NP or #SS
> (if stack switch fails).
> 
> Thus this warning can be user triggred and has very little value.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>   arch/x86/kvm/svm/svm.c | 9 ---------
>   1 file changed, 9 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index e9cec1b692051c..36f651ce842174 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -3428,15 +3428,6 @@ static int svm_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
>   		return 0;
>   	}
>   
> -	if (is_external_interrupt(svm->vmcb->control.exit_int_info) &&
> -	    exit_code != SVM_EXIT_EXCP_BASE + PF_VECTOR &&
> -	    exit_code != SVM_EXIT_NPF && exit_code != SVM_EXIT_TASK_SWITCH &&
> -	    exit_code != SVM_EXIT_INTR && exit_code != SVM_EXIT_NMI)
> -		printk(KERN_ERR "%s: unexpected exit_int_info 0x%x "
> -		       "exit_code 0x%x\n",
> -		       __func__, svm->vmcb->control.exit_int_info,
> -		       exit_code);
> -
>   	if (exit_fastpath != EXIT_FASTPATH_NONE)
>   		return 1;
>   

This was the only caller of is_external_interrupt() - should the 
definition be removed also to avoid a 'defined but not used' warning?

Regards,
Liam
Maxim Levitsky Nov. 9, 2022, 9:15 a.m. UTC | #2 
On Sun, 2022-11-06 at 15:53 +0000, Liam Merwick wrote:
> On 03/11/2022 14:13, Maxim Levitsky wrote:
> > It is valid to receive external interrupt and have broken IDT entry,
> > which will lead to #GP with exit_int_into that will contain the index of
> > the IDT entry (e.g any value).
> > 
> > Other exceptions can happen as well, like #NP or #SS
> > (if stack switch fails).
> > 
> > Thus this warning can be user triggred and has very little value.
> > 
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> > ---
> >   arch/x86/kvm/svm/svm.c | 9 ---------
> >   1 file changed, 9 deletions(-)
> > 
> > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > index e9cec1b692051c..36f651ce842174 100644
> > --- a/arch/x86/kvm/svm/svm.c
> > +++ b/arch/x86/kvm/svm/svm.c
> > @@ -3428,15 +3428,6 @@ static int svm_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
> >                 return 0;
> >         }
> >   
> > -       if (is_external_interrupt(svm->vmcb->control.exit_int_info) &&
> > -           exit_code != SVM_EXIT_EXCP_BASE + PF_VECTOR &&
> > -           exit_code != SVM_EXIT_NPF && exit_code != SVM_EXIT_TASK_SWITCH &&
> > -           exit_code != SVM_EXIT_INTR && exit_code != SVM_EXIT_NMI)
> > -               printk(KERN_ERR "%s: unexpected exit_int_info 0x%x "
> > -                      "exit_code 0x%x\n",
> > -                      __func__, svm->vmcb->control.exit_int_info,
> > -                      exit_code);
> > -
> >         if (exit_fastpath != EXIT_FASTPATH_NONE)
> >                 return 1;
> >   
> 
> This was the only caller of is_external_interrupt() - should the 
> definition be removed also to avoid a 'defined but not used' warning?

I hate to say it but I have seen a warning about an unused function,
but I really didn't expect that to come from this patch.
I somehow thought that its some leftover in kvm/queue.

I'll remove the unused function in a next version.

Best regards,
	Maxim Levitsky

> 
> Regards,
> Liam
>
Liam Merwick Nov. 21, 2022, 4:34 p.m. UTC | #3 
On 09/11/2022 09:15, Maxim Levitsky wrote:
> On Sun, 2022-11-06 at 15:53 +0000, Liam Merwick wrote:
>> On 03/11/2022 14:13, Maxim Levitsky wrote:
>>> It is valid to receive external interrupt and have broken IDT entry,
>>> which will lead to #GP with exit_int_into that will contain the index of
>>> the IDT entry (e.g any value).
>>>
>>> Other exceptions can happen as well, like #NP or #SS
>>> (if stack switch fails).
>>>
>>> Thus this warning can be user triggred and has very little value.
>>>
>>> Cc: stable@vger.kernel.org
>>> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
>>> ---
>>>    arch/x86/kvm/svm/svm.c | 9 ---------
>>>    1 file changed, 9 deletions(-)
>>>
>>> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
>>> index e9cec1b692051c..36f651ce842174 100644
>>> --- a/arch/x86/kvm/svm/svm.c
>>> +++ b/arch/x86/kvm/svm/svm.c
>>> @@ -3428,15 +3428,6 @@ static int svm_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
>>>                  return 0;
>>>          }
>>>    
>>> -       if (is_external_interrupt(svm->vmcb->control.exit_int_info) &&
>>> -           exit_code != SVM_EXIT_EXCP_BASE + PF_VECTOR &&
>>> -           exit_code != SVM_EXIT_NPF && exit_code != SVM_EXIT_TASK_SWITCH &&
>>> -           exit_code != SVM_EXIT_INTR && exit_code != SVM_EXIT_NMI)
>>> -               printk(KERN_ERR "%s: unexpected exit_int_info 0x%x "
>>> -                      "exit_code 0x%x\n",
>>> -                      __func__, svm->vmcb->control.exit_int_info,
>>> -                      exit_code);
>>> -
>>>          if (exit_fastpath != EXIT_FASTPATH_NONE)
>>>                  return 1;
>>>    
>>
>> This was the only caller of is_external_interrupt() - should the
>> definition be removed also to avoid a 'defined but not used' warning?
> 
> I hate to say it but I have seen a warning about an unused function,
> but I really didn't expect that to come from this patch.
> I somehow thought that its some leftover in kvm/queue.
> 
> I'll remove the unused function in a next version.
> 

Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
diff mbox series

Patch

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index e9cec1b692051c..36f651ce842174 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3428,15 +3428,6 @@  static int svm_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 		return 0;
 	}
 
-	if (is_external_interrupt(svm->vmcb->control.exit_int_info) &&
-	    exit_code != SVM_EXIT_EXCP_BASE + PF_VECTOR &&
-	    exit_code != SVM_EXIT_NPF && exit_code != SVM_EXIT_TASK_SWITCH &&
-	    exit_code != SVM_EXIT_INTR && exit_code != SVM_EXIT_NMI)
-		printk(KERN_ERR "%s: unexpected exit_int_info 0x%x "
-		       "exit_code 0x%x\n",
-		       __func__, svm->vmcb->control.exit_int_info,
-		       exit_code);
-
 	if (exit_fastpath != EXIT_FASTPATH_NONE)
 		return 1;