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    SubjectRe: [PATCH v5 4/9] KVM-HV: KVM Steal time implementation
    On Mon, Jul 04, 2011 at 11:32:23AM -0400, 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, while the vcpu had meaningful work to do - halt
    > time does not count.
    >
    > This information is acquired through the run_delay field of
    > delayacct/schedstats infrastructure, that counts time spent in a
    > runqueue but not running.
    >
    > Steal time is a per-cpu information, so the traditional MSR-based
    > infrastructure is used. A new msr, KVM_MSR_STEAL_TIME, holds the
    > memory area address containing information about steal time
    >
    > This patch contains the hypervisor part of the steal time infrasructure,
    > and can be backported independently of the guest portion.
    >
    > Signed-off-by: Glauber Costa <glommer@redhat.com>
    > CC: Rik van Riel <riel@redhat.com>
    > CC: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    > CC: Peter Zijlstra <peterz@infradead.org>
    > CC: Avi Kivity <avi@redhat.com>
    > CC: Anthony Liguori <aliguori@us.ibm.com>
    > CC: Eric B Munson <emunson@mgebm.net>
    > ---
    > arch/x86/include/asm/kvm_host.h | 8 +++++
    > arch/x86/include/asm/kvm_para.h | 4 +++
    > arch/x86/kvm/Kconfig | 1 +
    > arch/x86/kvm/x86.c | 56 ++++++++++++++++++++++++++++++++++++--
    > 4 files changed, 66 insertions(+), 3 deletions(-)
    >
    > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    > index da6bbee..9ba354d 100644
    > --- a/arch/x86/include/asm/kvm_host.h
    > +++ b/arch/x86/include/asm/kvm_host.h
    > @@ -389,6 +389,14 @@ struct kvm_vcpu_arch {
    > unsigned int hw_tsc_khz;
    > unsigned int time_offset;
    > struct page *time_page;
    > +
    > + struct {
    > + u64 msr_val;
    > + u64 last_steal;
    > + struct gfn_to_hva_cache stime;
    > + struct kvm_steal_time steal;
    > + } st;
    > +
    > u64 last_guest_tsc;
    > u64 last_kernel_ns;
    > u64 last_tsc_nsec;
    > diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
    > index 65f8bb9..c484ba8 100644
    > --- a/arch/x86/include/asm/kvm_para.h
    > +++ b/arch/x86/include/asm/kvm_para.h
    > @@ -45,6 +45,10 @@ struct kvm_steal_time {
    > __u32 pad[12];
    > };
    >
    > +#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)
    > +
    > #define KVM_MAX_MMU_OP_BATCH 32
    >
    > #define KVM_ASYNC_PF_ENABLED (1 << 0)
    > diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
    > index 50f6364..99c3f05 100644
    > --- a/arch/x86/kvm/Kconfig
    > +++ b/arch/x86/kvm/Kconfig
    > @@ -31,6 +31,7 @@ config KVM
    > select KVM_ASYNC_PF
    > select USER_RETURN_NOTIFIER
    > select KVM_MMIO
    > + select TASK_DELAY_ACCT
    > ---help---
    > Support hosting fully virtualized guest machines using hardware
    > virtualization extensions. You will need a fairly recent
    > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    > index 7167717..237bcdc 100644
    > --- a/arch/x86/kvm/x86.c
    > +++ b/arch/x86/kvm/x86.c
    > @@ -808,12 +808,12 @@ EXPORT_SYMBOL_GPL(kvm_get_dr);
    > * kvm-specific. Those are put in the beginning of the list.
    > */
    >
    > -#define KVM_SAVE_MSRS_BEGIN 8
    > +#define KVM_SAVE_MSRS_BEGIN 9
    > static u32 msrs_to_save[] = {
    > MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
    > MSR_KVM_SYSTEM_TIME_NEW, MSR_KVM_WALL_CLOCK_NEW,
    > HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,
    > - HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN,
    > + HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
    > MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP,
    > MSR_STAR,
    > #ifdef CONFIG_X86_64
    > @@ -1491,6 +1491,27 @@ static void kvmclock_reset(struct kvm_vcpu *vcpu)
    > }
    > }
    >
    > +static void record_steal_time(struct kvm_vcpu *vcpu)
    > +{
    > + u64 delta;
    > +
    > + if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
    > + return;
    > +
    > + if (unlikely(kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
    > + &vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
    > + return;

    The guest memory page is not pinned, sleeping via
    __copy_from_user/to_user is not allowed in vcpu_load context. Either pin
    it or use atomic acessors.

    > + case MSR_KVM_STEAL_TIME:
    > + vcpu->arch.st.msr_val = data;
    > +
    > + if (!(data & KVM_MSR_ENABLED)) {
    > + break;
    > + }

    On failure below this point, msr_val should be cleared of KVM_MSR_ENABLED?

    > +
    > + if (unlikely(!sched_info_on()))
    > + break;
    > +
    > + if (data & KVM_STEAL_RESERVED_MASK)
    > + return 1;
    > +
    > + if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.st.stime,
    > + data & KVM_STEAL_VALID_BITS))
    > + return 1;
    > +
    > + vcpu->arch.st.last_steal = current->sched_info.run_delay;
    > +
    > + record_steal_time(vcpu);
    > + break;
    > +


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