linux-kernel - Re: [PATCH v2 9/9] KVM: x86: remove exit_int_info warning in svm_handle

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Date:   Mon, 21 Nov 2022 16:34:47 +0000
From:   Liam Merwick <liam.merwick@...cle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Chenyi Qiang <chenyi.qiang@...el.com>,
        Yang Zhong <yang.zhong@...el.com>, x86@...nel.org,
        Shuah Khan <shuah@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        Borislav Petkov <bp@...en8.de>, Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        linux-kselftest@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Wei Wang <wei.w.wang@...el.com>,
        David Matlack <dmatlack@...gle.com>, stable@...r.kernel.org,
        Liam Merwick <liam.merwick@...cle.com>
Subject: Re: [PATCH v2 9/9] KVM: x86: remove exit_int_info warning in
 svm_handle_exit

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@...r.kernel.org
>>> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.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@...cle.com>