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SubjectRe: [PATCH] KVM: arm/arm64: vgic: Restrict setting irq->targets only in GICv2
On Thu, 4 Apr 2019 12:30:15 +0000
Zenghui Yu <yuzenghui@huawei.com> wrote:

Hi,

> Commit ad275b8bb1e6 ("KVM: arm/arm64: vgic-new: vgic_init: implement
> vgic_init") had set irq->targets in kvm_vgic_vcpu_init(), regardless of
> the GIC architecture (v2 or v3). When the number of vcpu reaches 32
> (in v3), UBSAN will complain about it.

The first part looks similar to this one:
http://lists.infradead.org/pipermail/linux-arm-kernel/2019-March/637209.html

> ================================================================================
> UBSAN: Undefined behaviour in arch/arm64/kvm/../../../virt/kvm/arm/vgic/vgic-init.c:223:21
> shift exponent 32 is too large for 32-bit type 'unsigned int'
> CPU: 13 PID: 833 Comm: CPU 32/KVM Kdump: loaded Not tainted 5.1.0-rc1+ #16
> Hardware name: Huawei TaiShan 2280 /BC11SPCD, BIOS 1.58 10/24/2018
> Call trace:
> dump_backtrace+0x0/0x190
> show_stack+0x24/0x30
> dump_stack+0xc8/0x114
> ubsan_epilogue+0x14/0x50
> __ubsan_handle_shift_out_of_bounds+0x118/0x188
> kvm_vgic_vcpu_init+0x1d4/0x200
> kvm_arch_vcpu_init+0x3c/0x48
> kvm_vcpu_init+0xa8/0x100
> kvm_arch_vcpu_create+0x94/0x120
> kvm_vm_ioctl+0x57c/0xe58
> do_vfs_ioctl+0xc4/0x7f0
> ksys_ioctl+0x8c/0xa0
> __arm64_sys_ioctl+0x28/0x38
> el0_svc_common+0xa0/0x190
> el0_svc_handler+0x38/0x78
> el0_svc+0x8/0xc
> ================================================================================
>
> This patch Restricts setting irq->targets in GICv2, which only supports
> a maximum of eight PEs, to keep UBSAN quiet. And since irq->mpidr will
> only be used by SPI in GICv3, we decided to set mpidr to 0 for SGI and
> PPI.
>
> Like commit ab2d5eb03dbb ("KVM: arm/arm64: vgic: Always initialize the
> group of private IRQs"), we should also take the creating order of the
> VGIC and VCPUs into consideration.
>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Cc: Andre Przywara <andre.przywara@arm.com>
> Cc: Christoffer Dall <christoffer.dall@arm.com>
> Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
> ---
> virt/kvm/arm/vgic/vgic-init.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> index 3bdb31e..0cba92e 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
> + irq->mpidr = 0;
> + } else {
> irq->group = 0;
> + if (vcpu->vcpu_id < VGIC_V2_MAX_CPUS)
> + irq->targets = 1U << vcpu->vcpu_id;
> + }
> }
>
> if (!irqchip_in_kernel(vcpu->kvm))
> @@ -297,10 +300,13 @@ int vgic_init(struct kvm *kvm)
>
> for (i = 0; i < VGIC_NR_PRIVATE_IRQS; i++) {
> struct vgic_irq *irq = &vgic_cpu->private_irqs[i];
> - if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3)
> + if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3) {
> irq->group = 1;
> - else
> + irq->mpidr = 0;
> + } else {
> irq->group = 0;
> + irq->targets = 1U << vcpu->vcpu_id;
> + }

So why would you need this part? That does the same as above, doesn't it?

Cheers,
Andre.


> }
> }
>

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