Re: [PATCH v3 2/2] kvm: x86: Deliver MSI IRQ to only lowest prio cpu if msi_redir_hint is true

["Radim Krčmář" <rkrcmar@redhat.com>]

2015-03-16 19:30-0600, James Sullivan:
> An MSI interrupt should only be delivered to the lowest priority CPU
> when it has RH=1, regardless of the delivery mode. Modified
> kvm_is_dm_lowest_prio() to check for either irq->delivery_mode == APIC_DM_LOWPRI
> or irq->msi_redir_hint.
> 
> Moved kvm_is_dm_lowest_prio() into lapic.h and renamed to
> kvm_lowest_prio_delivery().
> 
> Changed a check in kvm_irq_delivery_to_apic_fast() from
> irq->delivery_mode == APIC_DM_LOWPRI to kvm_is_dm_lowest_prio().
> 
> Signed-off-by: James Sullivan <sullivan.james.f@gmail.com>
> ---

Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>

> diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
> @@ -31,6 +31,8 @@
>  #include "ioapic.h"
>  
> +#include "lapic.h"
> +

(No need for the empty line between them.)

> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> @@ -701,8 +701,7 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
>  		dst = map->logical_map[cid];
>  
>  		bitmap = apic_logical_id(map, mda);
> -

(It's polite to preserve blank lines.)

> -		if (irq->delivery_mode == APIC_DM_LOWEST) {
> +		if (kvm_lowest_prio_delivery(irq)) {

lapic.c does not directly include lapic.h, (gets pulled via irq.h)
it would be nicer to fix it here, but can also be done later ...

> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> @@ -168,6 +168,12 @@ static inline bool kvm_apic_has_events(struct kvm_vcpu *vcpu)
> +static inline bool kvm_lowest_prio_delivery(struct kvm_lapic_irq *irq)
> +{
> +	return (irq->delivery_mode == APIC_DM_LOWEST ||
> +			irq->msi_redir_hint);

(These parentheses improve readability?)