> On 6 Mar 2019, at 11:40, Andre Przywara <andre.przywara@xxxxxxx> wrote:
>
> 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.
Just for my education, “targets” seems defined as an u8,
so it looks like you were silently running out of bits before, no?
> 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@xxxxxxx>
> Reported-by: Dave Martin <dave.martin@xxxxxxx>
> ---
> 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 3bdb31eaed64..3172b2c916f1 100644
> --- a/virt/kvm/arm/vgic/vgic-init.c
> +++ b/virt/kvm/arm/vgic/vgic-init.c
> @@ -220,7 +220,6 @@ 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 */
> @@ -231,10 +230,14 @@ 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
>
