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    SubjectRe: [PATCH v2 2/6] KVM-HV: KVM Steal time implementation
    On 01/28/2011 09:52 PM, 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.
    >
    >
    > @@ -1528,16 +1528,23 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
    > vcpu->arch.time_page =
    > gfn_to_page(vcpu->kvm, data>> PAGE_SHIFT);
    >
    > - if (is_error_page(vcpu->arch.time_page)) {
    > - kvm_release_page_clean(vcpu->arch.time_page);
    > - vcpu->arch.time_page = NULL;
    > - }
    > break;
    > }

    Unrelated?

    > @@ -2106,6 +2120,25 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
    > kvm_migrate_timers(vcpu);
    > vcpu->cpu = cpu;
    > }
    > +
    > + if (vcpu->arch.this_time_out) {
    > + u64 to = (get_kernel_ns() - vcpu->arch.this_time_out);
    > + /*
    > + * using nanoseconds introduces noise, which accumulates easily
    > + * leading to big steal time values. We want, however, to keep the
    > + * interface nanosecond-based for future-proofness.
    > + */
    > + to /= NSEC_PER_USEC;
    > + to *= NSEC_PER_USEC;

    Seems there is a real problem and that this is just papering it over.
    I'd like to understand the root cause.

    > + vcpu->arch.time_out += to;
    > + kvm_write_guest(vcpu->kvm, (gpa_t)&st->steal,
    > + &vcpu->arch.time_out, sizeof(st->steal));

    Error check.

    > + vcpu->arch.sversion += 2;

    Doesn't survive live migration. You need to use the version from the
    guest area.

    > + kvm_write_guest(vcpu->kvm, (gpa_t)&st->version,
    > + &vcpu->arch.sversion, sizeof(st->version));
    > + /* is it possible to have 2 loads in sequence? */
    > + vcpu->arch.this_time_out = 0;
    > + }
    > }
    >

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



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