[RESEND PATCH] KVM: arm: VGIC: properly initialise private IRQ affinity

[Andre Przywara <andre.przywara@arm.com>]

At the moment we initialise the target *mask* of a virtual IRQ to the
VCPU it belongs to, even though this mask is only defined for GICv2 and
quickly runs out of bits for many GICv3 guests.
This behaviour triggers an UBSAN complaint for more than 32 VCPUs:
------
[ 5659.462377] UBSAN: Undefined behaviour in virt/kvm/arm/vgic/vgic-init.c:223:21
[ 5659.471689] shift exponent 32 is too large for 32-bit type 'unsigned int'
------
Also for GICv3 guests the reporting of TARGET in the "vgic-state" debugfs
dump is wrong, due to this very same problem.

Fix both issues by only initialising vgic_irq->targets for a vGICv2 guest,
and by initialising vgic_irq->mpdir for vGICv3 guests instead. We can't
use the actual MPIDR for that, as the VCPU's system register is not
initialised at this point yet. This is not really an issue, as ->mpidr
is just used for the debugfs output and the IROUTER MMIO register, which
does not exist in redistributors (dealing with SGIs and PPIs).

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reported-by: Dave Martin <dave.martin@arm.com>
---
Hi,

this came up here again, I think it fell through the cracks back in
March:
http://lists.infradead.org/pipermail/linux-arm-kernel/2019-March/637209.html

Cheers,
Andre.

 virt/kvm/arm/vgic/vgic-init.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index 80127ca9269f..8bce2f75e0c1 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -210,7 +210,6 @@ int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu)
 		irq->intid = i;
 		irq->vcpu = NULL;
 		irq->target_vcpu = vcpu;
-		irq->targets = 1U << vcpu->vcpu_id;
 		kref_init(&irq->refcount);
 		if (vgic_irq_is_sgi(i)) {
 			/* SGIs */
@@ -221,10 +220,14 @@ int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu)
 			irq->config = VGIC_CONFIG_LEVEL;
 		}
 
-		if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3)
+		if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3) {
 			irq->group = 1;
-		else
+			/* The actual MPIDR is not initialised at this point. */
+			irq->mpidr = 0;
+		} else {
 			irq->group = 0;
+			irq->targets = 1U << vcpu->vcpu_id;
+		}
 	}
 
 	if (!irqchip_in_kernel(vcpu->kvm))
-- 
2.17.1

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