Re: [RFC PATCH 1/2] Hyper-H reference counter

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On Mon, May 13, 2013 at 4:45 AM, Vadim Rozenfeld <vrozenfe@xxxxxxxxxx> wrote:
> Signed-off: Peter Lieven <pl@xxxxxxx>
> Signed-off: Gleb Natapov <gleb@xxxxxxxxxx>
> Signed-off: Vadim Rozenfeld <vrozenfe@xxxxxxxxxx>
>
> The following patch allows to activate Hyper-V
> reference time counter
> ---
>  arch/x86/include/asm/kvm_host.h    |  2 ++
>  arch/x86/include/uapi/asm/hyperv.h |  3 +++
>  arch/x86/kvm/x86.c                 | 25 ++++++++++++++++++++++++-
>  3 files changed, 29 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 3741c65..f0fee35 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -575,6 +575,8 @@ struct kvm_arch {
>         /* fields used by HYPER-V emulation */
>         u64 hv_guest_os_id;
>         u64 hv_hypercall;
> +       u64 hv_ref_count;
> +       u64 hv_tsc_page;
>
>         #ifdef CONFIG_KVM_MMU_AUDIT
>         int audit_point;
> diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
> index b80420b..9711819 100644
> --- a/arch/x86/include/uapi/asm/hyperv.h
> +++ b/arch/x86/include/uapi/asm/hyperv.h
> @@ -136,6 +136,9 @@
>  /* MSR used to read the per-partition time reference counter */
>  #define HV_X64_MSR_TIME_REF_COUNT              0x40000020
>
> +/* A partition's reference time stamp counter (TSC) page */
> +#define HV_X64_MSR_REFERENCE_TSC               0x40000021
> +
>  /* Define the virtual APIC registers */
>  #define HV_X64_MSR_EOI                         0x40000070
>  #define HV_X64_MSR_ICR                         0x40000071
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 094b5d9..1a4036d 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -843,7 +843,7 @@ EXPORT_SYMBOL_GPL(kvm_rdpmc);
>  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_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,HV_X64_MSR_TIME_REF_COUNT,
>         HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
>         MSR_KVM_PV_EOI_EN,
>         MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP,
> @@ -1764,6 +1764,8 @@ static bool kvm_hv_msr_partition_wide(u32 msr)
>         switch (msr) {
>         case HV_X64_MSR_GUEST_OS_ID:
>         case HV_X64_MSR_HYPERCALL:
> +       case HV_X64_MSR_REFERENCE_TSC:
> +       case HV_X64_MSR_TIME_REF_COUNT:
>                 r = true;
>                 break;
>         }
> @@ -1803,6 +1805,21 @@ static int set_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>                 if (__copy_to_user((void __user *)addr, instructions, 4))
>                         return 1;
>                 kvm->arch.hv_hypercall = data;
> +               kvm->arch.hv_ref_count = get_kernel_ns();
> +               break;
> +       }
> +       case HV_X64_MSR_REFERENCE_TSC: {
> +               u64 gfn;
> +               unsigned long addr;
> +               u32 tsc_ref;
> +               gfn = data >> HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_SHIFT;
> +               addr = gfn_to_hva(kvm, gfn);
> +               if (kvm_is_error_hva(addr))
> +                       return 1;
> +               tsc_ref = 0;
> +               if(__copy_to_user((void __user *)addr, &tsc_ref, sizeof(tsc_ref)))

Does this do the right thing when we're migrating?  How does usermode
learn that the guest page has been dirtied?

> +                       return 1;
> +               kvm->arch.hv_tsc_page = data;
>                 break;
>         }
>         default:
> @@ -2229,6 +2246,12 @@ static int get_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
>         case HV_X64_MSR_HYPERCALL:
>                 data = kvm->arch.hv_hypercall;
>                 break;
> +       case HV_X64_MSR_TIME_REF_COUNT:
> +               data = div_u64(get_kernel_ns() - kvm->arch.hv_ref_count,100);
> +               break;
> +       case HV_X64_MSR_REFERENCE_TSC:
> +               data = kvm->arch.hv_tsc_page;
> +               break;
>         default:
>                 vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
>                 return 1;
> --
> 1.8.1.2
>
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