arm64: KVM: vgic: deal with GIC sub-page alignment
The GIC CPU interface is always 4k aligned. If the host is using
64k pages, it is critical to place the guest's GICC interface at the
same relative alignment as the host's GICV. Failure to do so results
in an impossibility for the guest to deal with interrupts.
Add a KVM_DEV_ARM_VGIC_GRP_ADDR_OFFSET attribute for the VGIC, allowing
userspace to retrieve the GICV offset in a page. It becomes then trivial
to adjust the GICC base address for the guest.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
index 8b51c1a..056b782 100644
--- a/arch/arm/include/uapi/asm/kvm.h
+++ b/arch/arm/include/uapi/asm/kvm.h
@@ -174,6 +174,7 @@
#define KVM_DEV_ARM_VGIC_OFFSET_SHIFT 0
#define KVM_DEV_ARM_VGIC_OFFSET_MASK (0xffffffffULL << KVM_DEV_ARM_VGIC_OFFSET_SHIFT)
#define KVM_DEV_ARM_VGIC_GRP_NR_IRQS 3
+#define KVM_DEV_ARM_VGIC_GRP_ADDR_OFFSET 4
/* KVM_IRQ_LINE irq field index values */
#define KVM_ARM_IRQ_TYPE_SHIFT 24
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index b5cd6ed..5513de4 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -160,6 +160,7 @@
#define KVM_DEV_ARM_VGIC_OFFSET_SHIFT 0
#define KVM_DEV_ARM_VGIC_OFFSET_MASK (0xffffffffULL << KVM_DEV_ARM_VGIC_OFFSET_SHIFT)
#define KVM_DEV_ARM_VGIC_GRP_NR_IRQS 3
+#define KVM_DEV_ARM_VGIC_GRP_ADDR_OFFSET 4
/* KVM_IRQ_LINE irq field index values */
#define KVM_ARM_IRQ_TYPE_SHIFT 24
diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 7ded851..0572d71 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -2400,6 +2400,12 @@
r = put_user(dev->kvm->arch.vgic.nr_irqs, uaddr);
break;
}
+ case KVM_DEV_ARM_VGIC_GRP_ADDR_OFFSET: {
+ u32 __user *uaddr = (u32 __user *)(long)attr->addr;
+ u32 val = vgic->vcpu_base & ~PAGE_MASK;
+ r = put_user(val, uaddr);
+ break;
+ }
}
@@ -2437,6 +2443,7 @@
offset = attr->attr & KVM_DEV_ARM_VGIC_OFFSET_MASK;
return vgic_has_attr_regs(vgic_cpu_ranges, offset);
case KVM_DEV_ARM_VGIC_GRP_NR_IRQS:
+ case KVM_DEV_ARM_VGIC_GRP_ADDR_OFFSET:
return 0;
}
return -ENXIO;
