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

[Paolo Bonzini <pbonzini@redhat.com>]

Il 13/05/2013 13:45, Vadim Rozenfeld ha scritto:
> Signed-off: Peter Lieven <pl@dlh.net>
> Signed-off: Gleb Natapov <gleb@redhat.com>
> Signed-off: Vadim Rozenfeld <vrozenfe@redhat.com>
> 
> 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)))
> +			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;

For migration, this should probably be writable from userspace
(msr_info->host_initiated in kvm_set_msr_common).

However, the spec says that the reference counter must count up from 0
_when the partition is created_, not when you initialize the
enlightenments.  Perhaps we can just piggy back on the kvmclock ioctls
and remove hv_ref_count altogether.  Then userspace doesn't need to
write to HV_X64_MSR_TIME_REF_COUNT.

Paolo

> +	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;
>