KVM: arm/arm64: VGIC: Properly initialise private IRQ affinity [Linux 4.19.72]

This Linux kernel change "KVM: arm/arm64: VGIC: Properly initialise private IRQ affinity" is included in the Linux 4.19.72 release. This change is authored by Andre Przywara <andre.przywara [at] arm.com> on Fri Aug 23 11:34:16 2019 +0100. The commit for this change in Linux stable tree is b8727df (patch) which is from upstream commit 2e16f3e. The same Linux upstream change may have been applied to various maintained Linux releases and you can find all Linux releases containing changes from upstream 2e16f3e.

KVM: arm/arm64: VGIC: Properly initialise private IRQ affinity

[ Upstream commit 2e16f3e926ed48373c98edea85c6ad0ef69425d1 ]

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.

Because there is no requirement to create the VGIC device before the
VCPUs (and QEMU actually does it the other way round), we can't safely
initialise mpidr or targets in kvm_vgic_vcpu_init(). But since we touch
every private IRQ for each VCPU anyway later (in vgic_init()), we can
just move the initialisation of those fields into there, where we
definitely know the VGIC type.

On the way make sure we really have either a VGICv2 or a VGICv3 device,
since the existing code is just checking for "VGICv3 or not", silently
ignoring the uninitialised case.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reported-by: Dave Martin <dave.martin@arm.com>
Tested-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

There are 30 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 virt/kvm/arm/vgic/vgic-init.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index 8196e4f..cd75df2 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -19,6 +19,7 @@
 #include <linux/cpu.h>
 #include <linux/kvm_host.h>
 #include <kvm/arm_vgic.h>
+#include <asm/kvm_emulate.h>
 #include <asm/kvm_mmu.h>
 #include "vgic.h"

@@ -175,12 +176,18 @@ static int kvm_vgic_dist_init(struct kvm *kvm, unsigned int nr_spis)
        irq->vcpu = NULL;
        irq->target_vcpu = vcpu0;
        kref_init(&irq->refcount);
-       if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V2) {
+       switch (dist->vgic_model) {
+       case KVM_DEV_TYPE_ARM_VGIC_V2:
            irq->targets = 0;
            irq->group = 0;
-       } else {
+           break;
+       case KVM_DEV_TYPE_ARM_VGIC_V3:
            irq->mpidr = 0;
            irq->group = 1;
+           break;
+       default:
+           kfree(dist->spis);
+           return -EINVAL;
        }
    }
    return 0;
@@ -220,7 +227,6 @@ 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 */
@@ -230,11 +236,6 @@ int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu)
            /* PPIs */
            irq->config = VGIC_CONFIG_LEVEL;
        }
-
-       if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3)
-           irq->group = 1;
-       else
-           irq->group = 0;
    }

    if (!irqchip_in_kernel(vcpu->kvm))
@@ -297,10 +298,19 @@ 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)
+           switch (dist->vgic_model) {
+           case KVM_DEV_TYPE_ARM_VGIC_V3:
                irq->group = 1;
-           else
+               irq->mpidr = kvm_vcpu_get_mpidr_aff(vcpu);
+               break;
+           case KVM_DEV_TYPE_ARM_VGIC_V2:
                irq->group = 0;
+               irq->targets = 1U << idx;
+               break;
+           default:
+               ret = -EINVAL;
+               goto out;
+           }
        }
    }

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