Re: [PATCH RFC] kvm: ignore apic polarity

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 2014-02-27 at 19:05 +0200, Michael S. Tsirkin wrote:
> apic polarity in KVM does not work: too many things assume active high.
> Let's not pretend it works, let's just ignore polarity flag.  If we ever
> want to emulate it exactly, this will need a feature flag anyway.
> 
> Also report this to userspace: this makes it
> possible to report the interrupt active-low
> in ACPI, this way we are closer to real hardware.
> 
> This patch fixes OSX running on KVM.
> 
> Reported-by: "Gabriel L. Somlo" <gsomlo@gmail.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> 
> ---
> 
> Gabriel, could you confirm this fixes OSX for you?
> If you can play with linux tweaking interrupt
> to active low, that would be very nice too:
> it's weekend here.
> 
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 902f124..db29b27 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -674,6 +676,7 @@ struct kvm_ppc_smmu_info {
>  #define KVM_CAP_ARM_EL1_32BIT 93
>  #define KVM_CAP_SPAPR_MULTITCE 94
>  #define KVM_CAP_EXT_EMUL_CPUID 95
> +#define KVM_CAP_X86_IOAPIC_POLARITY_IGNORED 96
>  
>  #ifdef KVM_CAP_IRQ_ROUTING
>  
> diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
> index 2d68297..ad170b4 100644
> --- a/virt/kvm/ioapic.c
> +++ b/virt/kvm/ioapic.c
> @@ -328,7 +328,6 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int irq_source_id,
>  	irq_level = __kvm_irq_line_state(&ioapic->irq_states[irq],
>  					 irq_source_id, level);
>  	entry = ioapic->redirtbl[irq];
> -	irq_level ^= entry.fields.polarity;
>  	if (!irq_level) {
>  		ioapic->irr &= ~mask;
>  		ret = 1;

I've run Windows and Linux guests with vfio assigned devices with this
change and all the interrupt types seem to work.

Tested-by: Alex Williamson <alex.williamson@redhat.com>