linux-kernel - Re: linux-next: manual merge of the kvm-arm tree with Linus' tree

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Date:	Thu, 16 Apr 2015 21:10:44 +0200
From:	Christoffer Dall <christoffer.dall@...aro.org>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Christoffer Dall <cdall@...columbia.edu>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Marc Zyngier <marc.zyngier@....com>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	kvmarm@...ts.cs.columbia.edu,
	Alex Bennée <alex.bennee@...aro.org>
Subject: Re: linux-next: manual merge of the kvm-arm tree with Linus' tree

Hi Paolo and Marc,

On Tue, Apr 07, 2015 at 06:20:15PM +0200, Paolo Bonzini wrote:
> 
> 
> On 18/03/2015 08:55, Christoffer Dall wrote:
> > Hi Stephen,
> > 
> > On Wed, Mar 18, 2015 at 02:41:11PM +1100, Stephen Rothwell wrote:
> >> Hi all,
> >>
> >> Today's linux-next merge of the kvm-arm tree got a conflict in
> >> virt/kvm/arm/vgic.c between commit ae705930fca6 ("arm/arm64: KVM: Keep
> >> elrsr/aisr in sync with software model") from Linus' tree and commit
> >> 71760950bf3d ("arm/arm64: KVM: add a common vgic_queue_irq_to_lr fn")
> >> from the kvm-arm tree.
> >>
> >> I fixed it up (I think - see below) and can carry the fix as necessary
> >> (no action is required).
> >>
> >> -- 
> >> Cheers,
> >> Stephen Rothwell                    sfr@...b.auug.org.au
> >>
> >> diff --cc virt/kvm/arm/vgic.c
> >> index c9f60f524588,ffd937ca5141..000000000000
> >> --- a/virt/kvm/arm/vgic.c
> >> +++ b/virt/kvm/arm/vgic.c
> >> @@@ -982,9 -1092,7 +1098,8 @@@ bool vgic_queue_irq(struct kvm_vcpu *vc
> >>   		if (vlr.source == sgi_source_id) {
> >>   			kvm_debug("LR%d piggyback for IRQ%d\n", lr, vlr.irq);
> >>   			BUG_ON(!test_bit(lr, vgic_cpu->lr_used));
> >> - 			vlr.state |= LR_STATE_PENDING;
> >> - 			vgic_set_lr(vcpu, lr, vlr);
> >> + 			vgic_queue_irq_to_lr(vcpu, irq, lr, vlr);
> >>  +			vgic_sync_lr_elrsr(vcpu, lr, vlr);
> >>   			return true;
> >>   		}
> >>   	}
> >> @@@ -1001,12 -1109,8 +1116,9 @@@
> >>   
> >>   	vlr.irq = irq;
> >>   	vlr.source = sgi_source_id;
> >> - 	vlr.state = LR_STATE_PENDING;
> >> - 	if (!vgic_irq_is_edge(vcpu, irq))
> >> - 		vlr.state |= LR_EOI_INT;
> >> - 
> >> - 	vgic_set_lr(vcpu, lr, vlr);
> >> + 	vlr.state = 0;
> >> + 	vgic_queue_irq_to_lr(vcpu, irq, lr, vlr);
> >>  +	vgic_sync_lr_elrsr(vcpu, lr, vlr);
> >>   
> >>   	return true;
> >>   }
> > 
> > Looks great, thanks!
> > -Christoffer
> 
> Got the same conflict when pulling from the kvm-arm tree, I used
> a different resolution though:
> 
> diff --cc virt/kvm/arm/vgic.c
> index c9f60f524588,b70174e74868..8d550ff14700
> --- a/virt/kvm/arm/vgic.c
> +++ b/virt/kvm/arm/vgic.c
> @@@ -955,6 -1095,25 +1101,26 @@@ static void vgic_retire_disabled_irqs(s
>   	}
>   }
>   
> + static void vgic_queue_irq_to_lr(struct kvm_vcpu *vcpu, int irq,
> + 				 int lr_nr, struct vgic_lr vlr)
> + {
> + 	if (vgic_irq_is_active(vcpu, irq)) {
> + 		vlr.state |= LR_STATE_ACTIVE;
> + 		kvm_debug("Set active, clear distributor: 0x%x\n", vlr.state);
> + 		vgic_irq_clear_active(vcpu, irq);
> + 		vgic_update_state(vcpu->kvm);
> + 	} else if (vgic_dist_irq_is_pending(vcpu, irq)) {
> + 		vlr.state |= LR_STATE_PENDING;
> + 		kvm_debug("Set pending: 0x%x\n", vlr.state);
> + 	}
> + 
> + 	if (!vgic_irq_is_edge(vcpu, irq))
> + 		vlr.state |= LR_EOI_INT;
> + 
> + 	vgic_set_lr(vcpu, lr_nr, vlr);
> ++	vgic_sync_lr_elrsr(vcpu, lr_nr, vlr);
> + }
> + 
>   /*
>    * Queue an interrupt to a CPU virtual interface. Return true on success,
>    * or false if it wasn't possible to queue it.
> @@@ -982,9 -1141,7 +1148,7 @@@ bool vgic_queue_irq(struct kvm_vcpu *vc
>                 if (vlr.source == sgi_source_id) {
>                         kvm_debug("LR%d piggyback for IRQ%d\n", lr, vlr.irq);
>                         BUG_ON(!test_bit(lr, vgic_cpu->lr_used));
> -                       vlr.state |= LR_STATE_PENDING;
> -                       vgic_set_lr(vcpu, lr, vlr);
> -                       vgic_sync_lr_elrsr(vcpu, lr, vlr);
> +                       vgic_queue_irq_to_lr(vcpu, irq, lr, vlr);
>                         return true;
>                 }
>         }
> @@@ -1001,12 -1158,8 +1165,8 @@@
>   
>         vlr.irq = irq;
>         vlr.source = sgi_source_id;
> -       vlr.state = LR_STATE_PENDING;
> -       if (!vgic_irq_is_edge(vcpu, irq))
> -               vlr.state |= LR_EOI_INT;
> - 
> -       vgic_set_lr(vcpu, lr, vlr);
> -       vgic_sync_lr_elrsr(vcpu, lr, vlr);
> +       vlr.state = 0;
> +       vgic_queue_irq_to_lr(vcpu, irq, lr, vlr);
>   
>         return true;
>   }
> 
> 
> Christoffer, this is the same logic as Stephen's resolution, but
> can you confirm that it makes sense "semantically" as well?
> 
> (Stephen, you'll still get the conflicts in linux-next for a
> couple of days as I finish local testing of KVM changes for 4.1).
> 
As it turns out, it was not the same logic as Stephen's resolution.
Stephen's resolution is bussy, because vlr is passed by value to
vgic_queue_irq_to_lr() and therefore the call to sync the elrsr does not
have any effect.

Unfortunately, it seems Paolo's more correct fix did not end up in
Linus' tree, so I guess I should just send a patch?

-Christoffer
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