On Sun, Dec 06, 2009 at 06:24:15PM +0100, Jan Kiszka wrote:
> 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.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
Can't you handle this in userspace entirely, only updating vcpu_events
state when appropriate?
Shouldnt the vcpu be stopped in the first place, when its state is
updated?
> ---
>
> Changes in v2:
> - invert selection logic
>
> Documentation/kvm/api.txt | 10 +++++++++-
> arch/x86/include/asm/kvm.h | 4 ++++
> arch/x86/kvm/x86.c | 9 ++++++---
> 3 files changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
> index e1a1141..b22592d 100644
> --- a/Documentation/kvm/api.txt
> +++ b/Documentation/kvm/api.txt
> @@ -685,7 +685,7 @@ struct kvm_vcpu_events {
> __u8 pad;
> } nmi;
> __u32 sipi_vector;
> - __u32 flags; /* must be zero */
> + __u32 flags;
> };
>
> 4.30 KVM_SET_VCPU_EVENTS
> @@ -701,6 +701,14 @@ vcpu.
>
> 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_SET_NMI_PENDING - transfer nmi.pending to the kernel
> +KVM_VCPUEVENT_SET_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..d1a67ae 100644
> --- a/arch/x86/include/asm/kvm.h
> +++ b/arch/x86/include/asm/kvm.h
> @@ -254,6 +254,10 @@ struct kvm_reinject_control {
> __u8 reserved[31];
> };
>
> +/* When set in flags, include corresponding fields on KVM_SET_VCPU_EVENTS */
> +#define KVM_VCPUEVENT_SET_NMI_PENDING 0x00000001
> +#define KVM_VCPUEVENT_SET_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 dd15d7a..e3c35ff 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1953,7 +1953,8 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu,
> 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_SET_NMI_PENDING | KVM_VCPUEVENT_SET_SIPI_VECTOR))
> return -EINVAL;
>
> vcpu_load(vcpu);
> @@ -1970,10 +1971,12 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
> 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_SET_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_SET_SIPI_VECTOR)
> + vcpu->arch.sipi_vector = events->sipi_vector;
>
> vcpu_put(vcpu);
>
>
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