[PATCH 39/43] KVM: arm64: gic-v5: Plumb in has/set/get_attr for sysregs & IRS MMIO regs

Sascha Bischoff
2026-04-27T16:20:52Z

The support for saving/restoring the GICv5 IRS's MMIO registers has
been added, as has the support for saving/restoring the ISTs. They are
however not yet callable from userspace. This commit changes that, and
actually plumbs these into the userspace API handlers.

Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
---
arch/arm64/kvm/vgic/vgic-kvm-device.c | 120 ++++++++++++++++++++++++--
1 file changed, 115 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c
index 944923121e080..2da93fb31769b 100644
--- a/arch/arm64/kvm/vgic/vgic-kvm-device.c
+++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c
@@ -533,7 +533,7 @@ int vgic_v3_parse_attr(struct kvm_device *dev, struct kvm_device_attr *attr,
* Allow access to certain ID-like registers prior to VGIC initialization,
* thereby allowing the VMM to provision the features / sizing of the VGIC.
*/
-static bool reg_allowed_pre_init(struct kvm_device_attr *attr)
+static bool v3_reg_allowed_pre_init(struct kvm_device_attr *attr)
{
if (attr->group != KVM_DEV_ARM_VGIC_GRP_DIST_REGS)
return false;
@@ -596,7 +596,7 @@ static int vgic_v3_attr_regs_access(struct kvm_device *dev,

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

- if (!(vgic_initialized(dev->kvm) || reg_allowed_pre_init(attr))) {
+ if (!(vgic_initialized(dev->kvm) || v3_reg_allowed_pre_init(attr))) {
ret = -EBUSY;
goto out;
}
@@ -788,14 +788,115 @@ int vgic_v5_parse_attr(struct kvm_device *dev,
return 0;
}

+/*
+ * Some registers can potentially be read before the core GIC & IRS has been
+ * initialised. Right now, everything is required to be post-init.
+ */
+static bool v5_reg_allowed_pre_init(struct kvm_device_attr *attr)
+{
+ return false;
+}
+
+/*
+ * vgic_v5_attr_regs_access - allows user space to access VGIC v5 state
+ *
+ * @dev: kvm device handle
+ * @attr: kvm device attribute
+ * @is_write: true if userspace is writing a register
+ */
+static int vgic_v5_attr_regs_access(struct kvm_device *dev,
+ struct kvm_device_attr *attr,
+ bool is_write)
+{
+ u64 __user *uaddr = (u64 __user *)(unsigned long)attr->addr;
+ struct vgic_reg_attr reg_attr;
+ gpa_t addr;
+ struct kvm_vcpu *vcpu;
+ bool uaccess;
+ u64 val;
+ int ret;
+
+ ret = vgic_v5_parse_attr(dev, attr, &reg_attr);
+ if (ret)
+ return ret;
+
+ vcpu = reg_attr.vcpu;
+ addr = reg_attr.addr;
+
+ switch (attr->group) {
+ case KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS:
+ /* Sysregs uaccess is performed by the sysreg handling code */
+ uaccess = false;
+ break;
+ case KVM_DEV_ARM_VGIC_GRP_IRS_REGS:
+ fallthrough;
+ default:
+ uaccess = true;
+ }
+
+ if (uaccess && is_write) {
+ if (get_user(val, uaddr))
+ return -EFAULT;
+ }
+
+ mutex_lock(&dev->kvm->lock);
+
+ if (kvm_trylock_all_vcpus(dev->kvm)) {
+ mutex_unlock(&dev->kvm->lock);
+ return -EBUSY;
+ }
+
+ mutex_lock(&dev->kvm->arch.config_lock);
+
+ if (!(vgic_initialized(dev->kvm) || v5_reg_allowed_pre_init(attr))) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ switch (attr->group) {
+ case KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS:
+ ret = vgic_v5_cpu_sysregs_uaccess(vcpu, attr, is_write);
+ break;
+ case KVM_DEV_ARM_VGIC_GRP_IRS_REGS:
+ /*
+ * The IRS registers are a mixture of 32-bit and 64-bit
+ * registers. Internally, we always perform the correctly sized
+ * access, but the UAPI is defined in such a way that we are
+ * always provided a __u64 by userspace. When userspace writes,
+ * the upper 32-bits are ignored for 32-bit accesses, and on a
+ * read any 32-bit accesses are written back to user memory
+ * using the full 64-bits.
+ */
+ ret = vgic_v5_irs_attr_regs_access(dev, attr, &val, is_write);
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+out:
+ mutex_unlock(&dev->kvm->arch.config_lock);
+ kvm_unlock_all_vcpus(dev->kvm);
+ mutex_unlock(&dev->kvm->lock);
+
+ if (!ret && uaccess && !is_write)
+ ret = put_user(val, uaddr);
+
+ return ret;
+}
+
static int vgic_v5_set_attr(struct kvm_device *dev,
struct kvm_device_attr *attr)
{
switch (attr->group) {
case KVM_DEV_ARM_VGIC_GRP_ADDR:
break;
+ case KVM_DEV_ARM_VGIC_GRP_IST:
+ return vgic_v5_irs_restore_ists(dev->kvm, attr);
+ case KVM_DEV_ARM_VGIC_GRP_IRS_REGS:
+ fallthrough;
case KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS:
- return -ENXIO;
+ return vgic_v5_attr_regs_access(dev, attr, true);
case KVM_DEV_ARM_VGIC_GRP_NR_IRQS:
break;
case KVM_DEV_ARM_VGIC_GRP_CTRL:
@@ -820,8 +921,12 @@ static int vgic_v5_get_attr(struct kvm_device *dev,
switch (attr->group) {
case KVM_DEV_ARM_VGIC_GRP_ADDR:
break;
+ case KVM_DEV_ARM_VGIC_GRP_IST:
+ return vgic_v5_irs_save_ists(dev->kvm, attr);
+ case KVM_DEV_ARM_VGIC_GRP_IRS_REGS:
+ fallthrough;
case KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS:
- return -ENXIO;
+ return vgic_v5_attr_regs_access(dev, attr, false);
case KVM_DEV_ARM_VGIC_GRP_NR_IRQS:
break;
case KVM_DEV_ARM_VGIC_GRP_CTRL:
@@ -851,8 +956,10 @@ static int vgic_v5_has_attr(struct kvm_device *dev,
return 0;
}
return -ENXIO;
+ case KVM_DEV_ARM_VGIC_GRP_IRS_REGS:
+ fallthrough;
case KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS:
- return -ENXIO;
+ return vgic_v5_has_attr_regs(dev, attr);
case KVM_DEV_ARM_VGIC_GRP_NR_IRQS:
return 0;
case KVM_DEV_ARM_VGIC_GRP_CTRL:
@@ -865,6 +972,9 @@ static int vgic_v5_has_attr(struct kvm_device *dev,
default:
return -ENXIO;
}
+ break;
+ case KVM_DEV_ARM_VGIC_GRP_IST:
+ return 0;
default:
return -ENXIO;
}
--
2.34.1