Re: [PATCH] KVM: i8259: initialize IMR to 0xff on reset

[Paolo Bonzini <pbonzini@redhat.com>]

On 08/30/2010 11:20 AM, Avi Kivity wrote:
> Otherwise, a wily interrupt can slip through while the guest isn't prepared
> for it (and while the irq base is zero).
>
> Signed-off-by: Avi Kivity<avi@redhat.com>
> ---
>   arch/x86/kvm/i8259.c |    2 +-
>   1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
> index 8d10c06..5de9ee0 100644
> --- a/arch/x86/kvm/i8259.c
> +++ b/arch/x86/kvm/i8259.c
> @@ -275,7 +275,7 @@ void kvm_pic_reset(struct kvm_kpic_state *s)
>
>   	s->last_irr = 0;
>   	s->irr = 0;
> -	s->imr = 0;
> +	s->imr = 0xff;
>   	s->isr = 0;
>   	s->isr_ack = 0xff;
>   	s->priority_add = 0;

Sounds sane, but the datasheet says explicitly that upon reset "The 
Interrupt Mask Register is cleared"...  (FWIW, I checked because it 
looked like QEMU and Xen also had the same behavior of setting IMR to zero).

Paolo