linux-kernel - Re: [PATCH v5 16/26] KVM: arm/arm64: GICv4: Propagate property updates to VLPIs

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Message-ID: <20171110083755.GI14144@cbox>
Date:   Fri, 10 Nov 2017 09:37:55 +0100
From:   Christoffer Dall <cdall@...aro.org>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Auger Eric <eric.auger@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Andre Przywara <Andre.Przywara@....com>,
        Shameerali Kolothum Thodi 
        <shameerali.kolothum.thodi@...wei.com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Shanker Donthineni <shankerd@...eaurora.org>
Subject: Re: [PATCH v5 16/26] KVM: arm/arm64: GICv4: Propagate property
 updates to VLPIs

On Wed, Nov 08, 2017 at 03:08:36PM +0000, Marc Zyngier wrote:
> On 07/11/17 21:28, Auger Eric wrote:
> > Hi Marc,
> > 
> > On 27/10/2017 16:28, Marc Zyngier wrote:
> >> Upon updating a property, we propagate it all the way to the physical
> >> ITS, and ask for an INV command to be executed there.
> >>
> >> Acked-by: Christoffer Dall <cdall@...aro.org>
> >> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> >> ---
> >>  virt/kvm/arm/vgic/vgic-its.c | 3 +++
> >>  1 file changed, 3 insertions(+)
> >>
> >> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> >> index 0b7e648e7a0c..2e77c7c83942 100644
> >> --- a/virt/kvm/arm/vgic/vgic-its.c
> >> +++ b/virt/kvm/arm/vgic/vgic-its.c
> >> @@ -296,6 +296,9 @@ static int update_lpi_config(struct kvm *kvm, struct vgic_irq *irq,
> >>  		spin_unlock(&irq->irq_lock);
> >>  	}
> >>  
> >> +	if (irq->hw)
> >> +		return its_prop_update_vlpi(irq->host_irq, prop, true);
> >> +
> >>  	return 0;
> >>  }
> > I am confused by the vgic_queue_irq_unlock() on the "hw" path. Why is it
> > needed in hw mode?
> 
> It's not. I guess we could bypass this altogether and take a short cut
> after having updated the priority and enabled fields.
> 

I can apply this on top of the series as well if you're happy with it:

commit b54fba93b1330803a59ca75f3a5102e22cadc871 (HEAD -> next-gicv4)
Author: Christoffer Dall <christoffer.dall@...aro.org>
Date:   Fri Nov 10 09:34:54 2017 +0100

    KVM: arm/arm64: Don't queue VLPIs on INV/INVALL
    
    Since VLPIs are injected directly by the hardware there's no need to
    mark these as pending in software and queue them on the AP list.
    
    Signed-off-by: Christoffer Dall <christoffer.dall@...aro.org>

diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index c93ecd4a903b..a3754ec719c4 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -292,11 +292,14 @@ static int update_lpi_config(struct kvm *kvm, struct vgic_irq *irq,
 		irq->priority = LPI_PROP_PRIORITY(prop);
 		irq->enabled = LPI_PROP_ENABLE_BIT(prop);
 
-		vgic_queue_irq_unlock(kvm, irq, flags);
-	} else {
-		spin_unlock_irqrestore(&irq->irq_lock, flags);
+		if (!irq->hw) {
+			vgic_queue_irq_unlock(kvm, irq, flags);
+			return 0;
+		}
 	}
 
+	spin_unlock_irqrestore(&irq->irq_lock, flags);
+
 	if (irq->hw)
 		return its_prop_update_vlpi(irq->host_irq, prop, needs_inv);
 


Thanks,
-Christoffer