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

[Paolo Bonzini]

On Thu, Jul 25, 2024 at 4:00 PM Liam Ni <zhiguangni01@xxxxxxxxx> 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@xxxxxxxxx>
> ---
>  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