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    SubjectRe: [PATCH v2 3/7] KVM-HV: KVM Steal time implementation
    On Sun, Jun 19, 2011 at 12:57:53PM +0300, Avi Kivity wrote:
    > On 06/17/2011 01:20 AM, Glauber Costa wrote:
    > >To implement steal time, we need the hypervisor to pass the guest information
    > >about how much time was spent running other processes outside the VM.
    > >This is per-vcpu, and using the kvmclock structure for that is an abuse
    > >we decided not to make.
    > >
    > >In this patchset, I am introducing a new msr, KVM_MSR_STEAL_TIME, that
    > >holds the memory area address containing information about steal time
    > >
    > >This patch contains the hypervisor part for it. I am keeping it separate from
    > >the headers to facilitate backports to people who wants to backport the kernel
    > >part but not the hypervisor, or the other way around.
    > >
    > >
    > >
    > >+#define KVM_STEAL_ALIGNMENT_BITS 5
    > >+#define KVM_STEAL_VALID_BITS ((-1ULL<< (KVM_STEAL_ALIGNMENT_BITS + 1)))
    > >+#define KVM_STEAL_RESERVED_MASK (((1<< KVM_STEAL_ALIGNMENT_BITS) - 1 )<< 1)
    >
    > Clumsy, but okay.
    >
    > >+static void record_steal_time(struct kvm_vcpu *vcpu)
    > >+{
    > >+ u64 delta;
    > >+
    > >+ if (vcpu->arch.st.stime&& vcpu->arch.st.this_time_out) {
    >
    > 0 is a valid value for stime.
    >
    > >+
    > >+ if (unlikely(kvm_read_guest(vcpu->kvm, vcpu->arch.st.stime,
    > >+ &vcpu->arch.st.steal, sizeof(struct kvm_steal_time)))) {
    > >+
    > >+ vcpu->arch.st.stime = 0;
    > >+ return;
    > >+ }
    > >+
    > >+ delta = (get_kernel_ns() - vcpu->arch.st.this_time_out);
    > >+
    > >+ vcpu->arch.st.steal.steal += delta;
    > >+ vcpu->arch.st.steal.version += 2;
    > >+
    > >+ if (unlikely(kvm_write_guest(vcpu->kvm, vcpu->arch.st.stime,
    > >+ &vcpu->arch.st.steal, sizeof(struct kvm_steal_time)))) {
    > >+
    > >+ vcpu->arch.st.stime = 0;
    > >+ return;
    > >+ }
    > >+ }
    > >+
    > >+}
    > >+
    > >
    > >@@ -2158,6 +2206,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
    > > kvm_migrate_timers(vcpu);
    > > vcpu->cpu = cpu;
    > > }
    > >+
    > >+ record_steal_time(vcpu);
    > > }
    >
    > This records time spent in userspace in the vcpu thread as steal
    > time. Is this what we want? Or just time preempted away?

    It also accounts halt time (kvm_vcpu_block) as steal time. Glauber, you
    could instead use the "runnable-state-but-waiting-in-runqueue" field of
    SCHEDSTATS, i forgot the exact name.



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