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    SubjectRe: [PATCH v4 1/4] KVM: X86: Add vCPU running/preempted state
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    On 13.11.2017 01:33, Wanpeng Li wrote:
    > From: Wanpeng Li <wanpeng.li@hotmail.com>
    >
    > This patch reuses the preempted field in kvm_steal_time, and will export
    > the vcpu running/pre-empted information to the guest from host. This will
    > enable guest to intelligently send ipi to running vcpus and set flag for
    > pre-empted vcpus. This will prevent waiting for vcpus that are not running.
    >
    > Cc: Paolo Bonzini <pbonzini@redhat.com>
    > Cc: Radim Krčmář <rkrcmar@redhat.com>
    > Cc: Peter Zijlstra <peterz@infradead.org>
    > Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
    > ---
    > arch/x86/include/uapi/asm/kvm_para.h | 3 +++
    > arch/x86/kernel/kvm.c | 2 +-
    > arch/x86/kvm/x86.c | 4 ++--
    > 3 files changed, 6 insertions(+), 3 deletions(-)
    >
    > diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
    > index 554aa8f..bf17b30 100644
    > --- a/arch/x86/include/uapi/asm/kvm_para.h
    > +++ b/arch/x86/include/uapi/asm/kvm_para.h
    > @@ -51,6 +51,9 @@ struct kvm_steal_time {
    > __u32 pad[11];
    > };
    >
    > +#define KVM_VCPU_NOT_PREEMPTED (0 << 0)
    > +#define KVM_VCPU_PREEMPTED (1 << 0)

    These should have a prefix that makes it obvious that they are used
    for kvm_steal_time/preempted.

    What about renaming preempted to "flags" or something like that.
    Then we could have

    KVM_STEAL_TIME_(FLAG_)PREEMPTED
    KVM_STEAL_TIME_(FLAG_)NOT_PREEMPTED

    > +
    > #define KVM_CLOCK_PAIRING_WALLCLOCK 0
    > struct kvm_clock_pairing {
    > __s64 sec;
    > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
    > index 8bb9594..1b1b641 100644
    > --- a/arch/x86/kernel/kvm.c
    > +++ b/arch/x86/kernel/kvm.c
    > @@ -608,7 +608,7 @@ __visible bool __kvm_vcpu_is_preempted(long cpu)
    > {
    > struct kvm_steal_time *src = &per_cpu(steal_time, cpu);
    >
    > - return !!src->preempted;
    > + return !!(src->preempted & KVM_VCPU_PREEMPTED);
    > }
    > PV_CALLEE_SAVE_REGS_THUNK(__kvm_vcpu_is_preempted);
    >
    > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    > index 03869eb..5e63033 100644
    > --- a/arch/x86/kvm/x86.c
    > +++ b/arch/x86/kvm/x86.c
    > @@ -2113,7 +2113,7 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
    > &vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
    > return;
    >
    > - vcpu->arch.st.steal.preempted = 0;
    > + vcpu->arch.st.steal.preempted = KVM_VCPU_NOT_PREEMPTED;
    >
    > if (vcpu->arch.st.steal.version & 1)
    > vcpu->arch.st.steal.version += 1; /* first time write, random junk */
    > @@ -2884,7 +2884,7 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
    > if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
    > return;
    >
    > - vcpu->arch.st.steal.preempted = 1;
    > + vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED;
    >
    > kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.st.stime,
    > &vcpu->arch.st.steal.preempted,
    >


    --

    Thanks,

    David / dhildenb

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