linux-kernel - Re: [PATCH] KVM:x86:Fix an interrupt injection logic error during PIC interrupt simulation

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Message-ID: <CABgObfYzEzZuDSKjB1SYcveTaRMaayvY8cvtPD8qGLvkDiwV5A@mail.gmail.com>
Date: Thu, 25 Jul 2024 16:17:11 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Liam Ni <zhiguangni01@...il.com>
Cc: Sean Christopherson <seanjc@...gle.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM:x86:Fix an interrupt injection logic error during PIC
 interrupt simulation

On Thu, Jul 25, 2024 at 4:00 PM Liam Ni <zhiguangni01@...il.com> wrote:
>
> The input parameter level to the pic_irq_request function indicates
> whether there are interrupts to be injected,
> a level value of 1 indicates that there are interrupts to be injected,
> and a level value of 0 indicates that there are no interrupts to be injected.
> And the value of level will be assigned to s->output,
> so we should set s->wakeup_needed to true when s->output is true.
>
> Signed-off-by: Liam Ni <zhiguangni01@...il.com>
> ---
>  arch/x86/kvm/i8259.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
> index 8dec646e764b..ec9d6ee7d33d 100644
> --- a/arch/x86/kvm/i8259.c
> +++ b/arch/x86/kvm/i8259.c
> @@ -567,7 +567,7 @@ static void pic_irq_request(struct kvm *kvm, int level)
>  {
>     struct kvm_pic *s = kvm->arch.vpic;
>
> -   if (!s->output)
> +   if (s->output)

This is the old value of s->output. wakeup is needed if you have a
0->1 transition, so what you're looking for is either

if (level)
  s->wakeup_needed = true;

or

if (!s->output && level)
  s->wakeup_needed = true;

but your version is incorrect because it would look for a 1->1
transition instead.

Thanks,

Paolo