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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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