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    SubjectRe: [PATCH v2 3/7] KVM-HV: KVM Steal time implementation
    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?


    --
    error compiling committee.c: too many arguments to function



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