On 22/08/2019 14:42, Andre Przywara wrote: > On Thu, 22 Aug 2019 01:13:32 +0800 > Zenghui Yu <yuzenghui@xxxxxxxxxx> wrote: > > Hi, > >> On 2019/8/22 1:00, Andre Przywara 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. >>> 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> >>> --- >>> 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) { >> >> I still think that if user-space create VCPUs before vGIC (like what >> Qemu does), the actual vGIC model will be unknown here. The UBSAN >> warning will still show up when booting a vGIC-v3 guest (with Qemu). > > Yes, you are right. I vaguely remembered this issue, but couldn't > find anything on the list about it. So thanks for the heads up! > > So I think I have a solution, where we drop the initialisation part > here altogether, instead initialise mpdir/targets together with the > group in vgic_init(). Unless there is some code which needs > irq->group before that point? You may want to check save/restore of a GICv3 guest using a mix of group-0/1 interrupts. I seem to remember some breakage in that area. > Will send a patch shortly. OK. In the meantime, I'll drop your initial patch. Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
