[PATCH v2 08/12] KVM: arm64: Allow userspace to configure a vCPU's virtual offset

Oliver Upton
2021-07-16T21:26:54Z

Add a new vCPU attribute that allows userspace to directly manipulate
the virtual counter-timer offset. Exposing such an interface allows for
the precise migration of guest virtual counter-timers, as it is an
indepotent interface.

Uphold the existing behavior of writes to CNTVOFF_EL2 for this new
interface, wherein a write to a single vCPU is broadcasted to all vCPUs
within a VM.

Signed-off-by: Oliver Upton <oupton@google.com>
---
arch/arm64/include/uapi/asm/kvm.h | 1 +
arch/arm64/kvm/arch_timer.c | 68 ++++++++++++++++++++++++++++++-
2 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index b3edde68bc3e..008d0518d2b1 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -365,6 +365,7 @@ struct kvm_arm_copy_mte_tags {
#define KVM_ARM_VCPU_TIMER_CTRL 1
#define KVM_ARM_VCPU_TIMER_IRQ_VTIMER 0
#define KVM_ARM_VCPU_TIMER_IRQ_PTIMER 1
+#define KVM_ARM_VCPU_TIMER_OFFSET_VTIMER 2
#define KVM_ARM_VCPU_PVTIME_CTRL 2
#define KVM_ARM_VCPU_PVTIME_IPA 0

diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
index 3df67c127489..d2b1b13af658 100644
--- a/arch/arm64/kvm/arch_timer.c
+++ b/arch/arm64/kvm/arch_timer.c
@@ -1305,7 +1305,7 @@ static void set_timer_irqs(struct kvm *kvm, int vtimer_irq, int ptimer_irq)
}
}

-int kvm_arm_timer_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
+int kvm_arm_timer_set_attr_irq(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
{
int __user *uaddr = (int __user *)(long)attr->addr;
struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
@@ -1338,7 +1338,39 @@ int kvm_arm_timer_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
return 0;
}

-int kvm_arm_timer_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
+int kvm_arm_timer_set_attr_offset(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
+{
+ u64 __user *uaddr = (u64 __user *)(long)attr->addr;
+ u64 offset;
+
+ if (get_user(offset, uaddr))
+ return -EFAULT;
+
+ switch (attr->attr) {
+ case KVM_ARM_VCPU_TIMER_OFFSET_VTIMER:
+ update_vtimer_cntvoff(vcpu, offset);
+ break;
+ default:
+ return -ENXIO;
+ }
+
+ return 0;
+}
+
+int kvm_arm_timer_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
+{
+ switch (attr->attr) {
+ case KVM_ARM_VCPU_TIMER_IRQ_VTIMER:
+ case KVM_ARM_VCPU_TIMER_IRQ_PTIMER:
+ return kvm_arm_timer_set_attr_irq(vcpu, attr);
+ case KVM_ARM_VCPU_TIMER_OFFSET_VTIMER:
+ return kvm_arm_timer_set_attr_offset(vcpu, attr);
+ }
+
+ return -ENXIO;
+}
+
+int kvm_arm_timer_get_attr_irq(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
{
int __user *uaddr = (int __user *)(long)attr->addr;
struct arch_timer_context *timer;
@@ -1359,11 +1391,43 @@ int kvm_arm_timer_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
return put_user(irq, uaddr);
}

+int kvm_arm_timer_get_attr_offset(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
+{
+ u64 __user *uaddr = (u64 __user *)(long)attr->addr;
+ struct arch_timer_context *timer;
+ u64 offset;
+
+ switch (attr->attr) {
+ case KVM_ARM_VCPU_TIMER_OFFSET_VTIMER:
+ timer = vcpu_vtimer(vcpu);
+ break;
+ default:
+ return -ENXIO;
+ }
+
+ offset = timer_get_offset(timer);
+ return put_user(offset, uaddr);
+}
+
+int kvm_arm_timer_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
+{
+ switch (attr->attr) {
+ case KVM_ARM_VCPU_TIMER_IRQ_VTIMER:
+ case KVM_ARM_VCPU_TIMER_IRQ_PTIMER:
+ return kvm_arm_timer_get_attr_irq(vcpu, attr);
+ case KVM_ARM_VCPU_TIMER_OFFSET_VTIMER:
+ return kvm_arm_timer_get_attr_offset(vcpu, attr);
+ }
+
+ return -ENXIO;
+}
+
int kvm_arm_timer_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
{
switch (attr->attr) {
case KVM_ARM_VCPU_TIMER_IRQ_VTIMER:
case KVM_ARM_VCPU_TIMER_IRQ_PTIMER:
+ case KVM_ARM_VCPU_TIMER_OFFSET_VTIMER:
return 0;
}

--
2.32.0.402.g57bb445576-goog