[PATCH v4 15/16] KVM: arm64: nv: Allow userland to set VGIC maintenance IRQ

Marc Zyngier
2025-02-25T17:29:48Z

From: Andre Przywara <andre.przywara@arm.com>

The VGIC maintenance IRQ signals various conditions about the LRs, when
the GIC's virtualization extension is used.
So far we didn't need it, but nested virtualization needs to know about
this interrupt, so add a userland interface to setup the IRQ number.
The architecture mandates that it must be a PPI, on top of that this code
only exports a per-device option, so the PPI is the same on all VCPUs.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
[added some bits of documentation]
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
.../virt/kvm/devices/arm-vgic-v3.rst | 12 +++++++-
arch/arm64/include/uapi/asm/kvm.h | 1 +
arch/arm64/kvm/vgic/vgic-kvm-device.c | 29 +++++++++++++++++--
tools/arch/arm/include/uapi/asm/kvm.h | 1 +
4 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/Documentation/virt/kvm/devices/arm-vgic-v3.rst b/Documentation/virt/kvm/devices/arm-vgic-v3.rst
index 5817edb4e0467..e860498b1e359 100644
--- a/Documentation/virt/kvm/devices/arm-vgic-v3.rst
+++ b/Documentation/virt/kvm/devices/arm-vgic-v3.rst
@@ -291,8 +291,18 @@ Groups:
| Aff3 | Aff2 | Aff1 | Aff0 |

Errors:
-
======= =============================================
-EINVAL vINTID is not multiple of 32 or info field is
not VGIC_LEVEL_INFO_LINE_LEVEL
======= =============================================
+
+ KVM_DEV_ARM_VGIC_GRP_MAINT_IRQ
+ Attributes:
+
+ The attr field of kvm_device_attr encodes the following values:
+
+ bits: | 31 .... 5 | 4 .... 0 |
+ values: | RES0 | vINTID |
+
+ The vINTID specifies which interrupt is generated when the vGIC
+ must generate a maintenance interrupt. This must be a PPI.
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 568bf858f3198..fc5a641b3ed6c 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -403,6 +403,7 @@ enum {
#define KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS 6
#define KVM_DEV_ARM_VGIC_GRP_LEVEL_INFO 7
#define KVM_DEV_ARM_VGIC_GRP_ITS_REGS 8
+#define KVM_DEV_ARM_VGIC_GRP_MAINT_IRQ 9
#define KVM_DEV_ARM_VGIC_LINE_LEVEL_INFO_SHIFT 10
#define KVM_DEV_ARM_VGIC_LINE_LEVEL_INFO_MASK \
(0x3fffffULL << KVM_DEV_ARM_VGIC_LINE_LEVEL_INFO_SHIFT)
diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c
index 5f4f57aaa23ec..359094f68c23e 100644
--- a/arch/arm64/kvm/vgic/vgic-kvm-device.c
+++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c
@@ -303,6 +303,12 @@ static int vgic_get_common_attr(struct kvm_device *dev,
VGIC_NR_PRIVATE_IRQS, uaddr);
break;
}
+ case KVM_DEV_ARM_VGIC_GRP_MAINT_IRQ: {
+ u32 __user *uaddr = (u32 __user *)(long)attr->addr;
+
+ r = put_user(dev->kvm->arch.vgic.mi_intid, uaddr);
+ break;
+ }
}

return r;
@@ -517,7 +523,7 @@ static int vgic_v3_attr_regs_access(struct kvm_device *dev,
struct vgic_reg_attr reg_attr;
gpa_t addr;
struct kvm_vcpu *vcpu;
- bool uaccess;
+ bool uaccess, post_init = true;
u32 val;
int ret;

@@ -533,6 +539,9 @@ static int vgic_v3_attr_regs_access(struct kvm_device *dev,
/* Sysregs uaccess is performed by the sysreg handling code */
uaccess = false;
break;
+ case KVM_DEV_ARM_VGIC_GRP_MAINT_IRQ:
+ post_init = false;
+ fallthrough;
default:
uaccess = true;
}
@@ -552,7 +561,7 @@ static int vgic_v3_attr_regs_access(struct kvm_device *dev,

mutex_lock(&dev->kvm->arch.config_lock);

- if (unlikely(!vgic_initialized(dev->kvm))) {
+ if (post_init != vgic_initialized(dev->kvm)) {
ret = -EBUSY;
goto out;
}
@@ -582,6 +591,19 @@ static int vgic_v3_attr_regs_access(struct kvm_device *dev,
}
break;
}
+ case KVM_DEV_ARM_VGIC_GRP_MAINT_IRQ:
+ if (!is_write) {
+ val = dev->kvm->arch.vgic.mi_intid;
+ ret = 0;
+ break;
+ }
+
+ ret = -EINVAL;
+ if ((val < VGIC_NR_PRIVATE_IRQS) && (val >= VGIC_NR_SGIS)) {
+ dev->kvm->arch.vgic.mi_intid = val;
+ ret = 0;
+ }
+ break;
default:
ret = -EINVAL;
break;
@@ -608,6 +630,7 @@ static int vgic_v3_set_attr(struct kvm_device *dev,
case KVM_DEV_ARM_VGIC_GRP_REDIST_REGS:
case KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS:
case KVM_DEV_ARM_VGIC_GRP_LEVEL_INFO:
+ case KVM_DEV_ARM_VGIC_GRP_MAINT_IRQ:
return vgic_v3_attr_regs_access(dev, attr, true);
default:
return vgic_set_common_attr(dev, attr);
@@ -622,6 +645,7 @@ static int vgic_v3_get_attr(struct kvm_device *dev,
case KVM_DEV_ARM_VGIC_GRP_REDIST_REGS:
case KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS:
case KVM_DEV_ARM_VGIC_GRP_LEVEL_INFO:
+ case KVM_DEV_ARM_VGIC_GRP_MAINT_IRQ:
return vgic_v3_attr_regs_access(dev, attr, false);
default:
return vgic_get_common_attr(dev, attr);
@@ -645,6 +669,7 @@ static int vgic_v3_has_attr(struct kvm_device *dev,
case KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS:
return vgic_v3_has_attr_regs(dev, attr);
case KVM_DEV_ARM_VGIC_GRP_NR_IRQS:
+ case KVM_DEV_ARM_VGIC_GRP_MAINT_IRQ:
return 0;
case KVM_DEV_ARM_VGIC_GRP_LEVEL_INFO: {
if (((attr->attr & KVM_DEV_ARM_VGIC_LINE_LEVEL_INFO_MASK) >>
diff --git a/tools/arch/arm/include/uapi/asm/kvm.h b/tools/arch/arm/include/uapi/asm/kvm.h
index 03cd7c19a683b..d5dd969028175 100644
--- a/tools/arch/arm/include/uapi/asm/kvm.h
+++ b/tools/arch/arm/include/uapi/asm/kvm.h
@@ -246,6 +246,7 @@ struct kvm_vcpu_events {
#define KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS 6
#define KVM_DEV_ARM_VGIC_GRP_LEVEL_INFO 7
#define KVM_DEV_ARM_VGIC_GRP_ITS_REGS 8
+#define KVM_DEV_ARM_VGIC_GRP_MAINT_IRQ 9
#define KVM_DEV_ARM_VGIC_LINE_LEVEL_INFO_SHIFT 10
#define KVM_DEV_ARM_VGIC_LINE_LEVEL_INFO_MASK \
(0x3fffffULL << KVM_DEV_ARM_VGIC_LINE_LEVEL_INFO_SHIFT)
--
2.39.2