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

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Date:   Wed, 09 Nov 2022 11:15:16 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Liam Merwick <liam.merwick@...cle.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
Subject: Re: [PATCH v2 9/9] KVM: x86: remove exit_int_info warning in
 svm_handle_exit

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.

Best regards,
	Maxim Levitsky

> 
> Regards,
> Liam
>