arm64 requires a vcpu fd (KVM_HAS_DEVICE_ATTR vcpu ioctl) to probe
support for steal-time. However this is unnecessary, as only a KVM
fd is required, and it complicates userspace (userspace may prefer
delaying vcpu creation until after feature probing). Introduce a cap
that can be checked instead. While x86 can already probe steal-time
support with a kvm fd (KVM_GET_SUPPORTED_CPUID), we add the cap there
too for consistency.
Reviewed-by: Steven Price <steven.price@xxxxxxx>
Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
---
Documentation/virt/kvm/api.rst | 11 +++++++++++
arch/arm64/include/asm/kvm_host.h | 1 +
arch/arm64/kvm/arm.c | 3 +++
arch/arm64/kvm/pvtime.c | 2 +-
arch/x86/kvm/x86.c | 3 +++
include/uapi/linux/kvm.h | 1 +
6 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 3bd96c1a3962..3716d1e29771 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6152,3 +6152,14 @@ KVM can therefore start protected VMs.
This capability governs the KVM_S390_PV_COMMAND ioctl and the
KVM_MP_STATE_LOAD MP_STATE. KVM_SET_MP_STATE can fail for protected
guests when the state change is invalid.
+
+8.24 KVM_CAP_STEAL_TIME
+-----------------------
+
+:Architectures: arm64, x86
+
+This capability indicates that KVM supports steal time accounting.
+When steal time accounting is supported it may be enabled with
+architecture-specific interfaces. For x86 see
+Documentation/virt/kvm/msr.rst "MSR_KVM_STEAL_TIME". For arm64 see
+Documentation/virt/kvm/devices/vcpu.rst "KVM_ARM_VCPU_PVTIME_CTRL".
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index b01f52b61572..8909c840ea91 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -500,6 +500,7 @@ long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu);
gpa_t kvm_init_stolen_time(struct kvm_vcpu *vcpu);
void kvm_update_stolen_time(struct kvm_vcpu *vcpu);
+bool kvm_arm_pvtime_supported(void);
int kvm_arm_pvtime_set_attr(struct kvm_vcpu *vcpu,
struct kvm_device_attr *attr);
int kvm_arm_pvtime_get_attr(struct kvm_vcpu *vcpu,
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 90cb90561446..0f7f8cd2f341 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -222,6 +222,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
*/
r = 1;
break;
+ case KVM_CAP_STEAL_TIME:
+ r = kvm_arm_pvtime_supported();
+ break;
default:
r = kvm_arch_vm_ioctl_check_extension(kvm, ext);
break;
diff --git a/arch/arm64/kvm/pvtime.c b/arch/arm64/kvm/pvtime.c
index 025b5f3a97ef..468bd1ef9c7e 100644
--- a/arch/arm64/kvm/pvtime.c
+++ b/arch/arm64/kvm/pvtime.c
@@ -73,7 +73,7 @@ gpa_t kvm_init_stolen_time(struct kvm_vcpu *vcpu)
return base;
}
-static bool kvm_arm_pvtime_supported(void)
+bool kvm_arm_pvtime_supported(void)
{
return !!sched_info_on();
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 88c593f83b28..27fc86bb28c4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3538,6 +3538,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
r = kvm_x86_ops.nested_ops->enable_evmcs != NULL;
break;
+ case KVM_CAP_STEAL_TIME:
+ r = sched_info_on();
+ break;
default:
break;
}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 4fdf30316582..121fb29ac004 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1031,6 +1031,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_PPC_SECURE_GUEST 181
#define KVM_CAP_HALT_POLL 182
#define KVM_CAP_ASYNC_PF_INT 183
+#define KVM_CAP_STEAL_TIME 184
#ifdef KVM_CAP_IRQ_ROUTING
--
2.25.4
