KVM: x86: Extend KVM_SET_VCPU_EVENTS with selective updates
User space may not want to overwrite asynchronously changing VCPU event
states on write-back. So allow to skip nmi.pending and sipi_vector by
setting corresponding bits in the flags field of kvm_vcpu_events.
[avi: advertise the bits in KVM_GET_VCPU_EVENTS]
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
index e1a1141..2811e45 100644
--- a/Documentation/kvm/api.txt
+++ b/Documentation/kvm/api.txt
@@ -685,7 +685,7 @@
__u8 pad;
} nmi;
__u32 sipi_vector;
- __u32 flags; /* must be zero */
+ __u32 flags;
};
4.30 KVM_SET_VCPU_EVENTS
@@ -701,6 +701,14 @@
See KVM_GET_VCPU_EVENTS for the data structure.
+Fields that may be modified asynchronously by running VCPUs can be excluded
+from the update. These fields are nmi.pending and sipi_vector. Keep the
+corresponding bits in the flags field cleared to suppress overwriting the
+current in-kernel state. The bits are:
+
+KVM_VCPUEVENT_VALID_NMI_PENDING - transfer nmi.pending to the kernel
+KVM_VCPUEVENT_VALID_SIPI_VECTOR - transfer sipi_vector
+
5. The kvm_run structure
diff --git a/arch/x86/include/asm/kvm.h b/arch/x86/include/asm/kvm.h
index 950df43..f46b79f 100644
--- a/arch/x86/include/asm/kvm.h
+++ b/arch/x86/include/asm/kvm.h
@@ -254,6 +254,10 @@
__u8 reserved[31];
};
+/* When set in flags, include corresponding fields on KVM_SET_VCPU_EVENTS */
+#define KVM_VCPUEVENT_VALID_NMI_PENDING 0x00000001
+#define KVM_VCPUEVENT_VALID_SIPI_VECTOR 0x00000002
+
/* for KVM_GET/SET_VCPU_EVENTS */
struct kvm_vcpu_events {
struct {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9d06896..6651dbf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1913,7 +1913,8 @@
events->sipi_vector = vcpu->arch.sipi_vector;
- events->flags = 0;
+ events->flags = (KVM_VCPUEVENT_VALID_NMI_PENDING
+ | KVM_VCPUEVENT_VALID_SIPI_VECTOR);
vcpu_put(vcpu);
}
@@ -1921,7 +1922,8 @@
static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
struct kvm_vcpu_events *events)
{
- if (events->flags)
+ if (events->flags & ~(KVM_VCPUEVENT_VALID_NMI_PENDING
+ | KVM_VCPUEVENT_VALID_SIPI_VECTOR))
return -EINVAL;
vcpu_load(vcpu);
@@ -1938,10 +1940,12 @@
kvm_pic_clear_isr_ack(vcpu->kvm);
vcpu->arch.nmi_injected = events->nmi.injected;
- vcpu->arch.nmi_pending = events->nmi.pending;
+ if (events->flags & KVM_VCPUEVENT_VALID_NMI_PENDING)
+ vcpu->arch.nmi_pending = events->nmi.pending;
kvm_x86_ops->set_nmi_mask(vcpu, events->nmi.masked);
- vcpu->arch.sipi_vector = events->sipi_vector;
+ if (events->flags & KVM_VCPUEVENT_VALID_SIPI_VECTOR)
+ vcpu->arch.sipi_vector = events->sipi_vector;
vcpu_put(vcpu);