Re: [PATCH 3/7] KVM-HV: KVM Steal time implementation

[Gleb Natapov]

On Mon, Jun 13, 2011 at 07:31:33PM -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.
> 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.
> 
> Signed-off-by: Glauber Costa <glommer@xxxxxxxxxx>
> CC: Rik van Riel <riel@xxxxxxxxxx>
> CC: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> CC: Avi Kivity <avi@xxxxxxxxxx>
> CC: Anthony Liguori <aliguori@xxxxxxxxxx>
> CC: Eric B Munson <emunson@xxxxxxxxx>
> ---
>  arch/x86/include/asm/kvm_host.h |    8 +++++
>  arch/x86/include/asm/kvm_para.h |    4 ++
>  arch/x86/kvm/x86.c              |   60 +++++++++++++++++++++++++++++++++++++--
>  3 files changed, 69 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index fc38eca..5dce014 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -388,6 +388,14 @@ struct kvm_vcpu_arch {
>  	unsigned int hw_tsc_khz;
>  	unsigned int time_offset;
>  	struct page *time_page;
> +
> +	struct {
> +		u64 msr_val;
> +		gpa_t stime;
> +		struct kvm_steal_time steal;
> +		u64 this_time_out;
> +	} 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 ac306c4..0341e61 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[6];
>  };
>  
> +#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/x86.c b/arch/x86/kvm/x86.c
> index 6645634..10fe028 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -797,12 +797,12 @@ 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
> @@ -1480,6 +1480,34 @@ static void kvmclock_reset(struct kvm_vcpu *vcpu)
>  	}
>  }
>  
> +static void record_steal_time(struct kvm_vcpu *vcpu)
> +{
> +	u64 delta;
> +
> +	if (vcpu->arch.st.stime && vcpu->arch.st.this_time_out) {
> +
> +		if (unlikely(kvm_read_guest(vcpu->kvm, vcpu->arch.st.stime,
> +			&vcpu->arch.st.steal, sizeof(struct kvm_steal_time)))) {
> +
> +			vcpu->arch.st.stime = 0;
> +			return;
> +		}
> +
> +		delta = (get_kernel_ns() - vcpu->arch.st.this_time_out);
> +
> +		vcpu->arch.st.steal.steal += delta;
> +		vcpu->arch.st.steal.version += 2;
> +
> +		if (unlikely(kvm_write_guest(vcpu->kvm, vcpu->arch.st.stime,
Why not use kvm_write_guest_cached() here and introduce kvm_read_guest_cached()
for the read above?

> +			&vcpu->arch.st.steal, sizeof(struct kvm_steal_time)))) {
> +
> +			vcpu->arch.st.stime = 0;
> +			return;
> +		}
> +	}
> +
> +}
> +
>  int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>  {
>  	switch (msr) {
> @@ -1562,6 +1590,23 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>  		if (kvm_pv_enable_async_pf(vcpu, data))
>  			return 1;
>  		break;
> +	case MSR_KVM_STEAL_TIME:
> +		vcpu->arch.st.msr_val = data;
> +
> +		if (!(data & KVM_MSR_ENABLED)) {
> +			vcpu->arch.st.stime = 0;
> +			break;
> +		}
> +
> +		if (data & KVM_STEAL_RESERVED_MASK)
> +			return 1;
> +
> +		vcpu->arch.st.this_time_out = get_kernel_ns();
> +		vcpu->arch.st.stime = data & KVM_STEAL_VALID_BITS;
> +		record_steal_time(vcpu);
> +
> +		break;
> +
>  	case MSR_IA32_MCG_CTL:
>  	case MSR_IA32_MCG_STATUS:
>  	case MSR_IA32_MC0_CTL ... MSR_IA32_MC0_CTL + 4 * KVM_MAX_MCE_BANKS - 1:
> @@ -1847,6 +1892,9 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
>  	case MSR_KVM_ASYNC_PF_EN:
>  		data = vcpu->arch.apf.msr_val;
>  		break;
> +	case MSR_KVM_STEAL_TIME:
> +		data = vcpu->arch.st.msr_val;
> +		break;
>  	case MSR_IA32_P5_MC_ADDR:
>  	case MSR_IA32_P5_MC_TYPE:
>  	case MSR_IA32_MCG_CAP:
> @@ -2158,6 +2206,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>  			kvm_migrate_timers(vcpu);
>  		vcpu->cpu = cpu;
>  	}
> +
> +	record_steal_time(vcpu);
>  }
>  
>  void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> @@ -2165,6 +2215,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>  	kvm_x86_ops->vcpu_put(vcpu);
>  	kvm_put_guest_fpu(vcpu);
>  	kvm_get_msr(vcpu, MSR_IA32_TSC, &vcpu->arch.last_guest_tsc);
> +	vcpu->arch.st.this_time_out = get_kernel_ns();
>  }
>  
Shouldn't we call record_steal_time(vcpu)/vcpu->arch.st.this_time_out = get_kernel_ns();
just before/after entering/exiting a guest? vcpu_(put|get) are called
for each vcpu ioctl, not only VCPU_RUN.

>  static int is_efer_nx(void)
> @@ -2477,7 +2528,8 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
>  			     (1 << KVM_FEATURE_NOP_IO_DELAY) |
>  			     (1 << KVM_FEATURE_CLOCKSOURCE2) |
>  			     (1 << KVM_FEATURE_ASYNC_PF) |
> -			     (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
> +			     (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
> +			     (1 << KVM_FEATURE_STEAL_TIME);
>  		entry->ebx = 0;
>  		entry->ecx = 0;
>  		entry->edx = 0;
> @@ -6200,6 +6252,8 @@ int kvm_arch_vcpu_reset(struct kvm_vcpu *vcpu)
>  
>  	kvmclock_reset(vcpu);
>  
> +	vcpu->arch.st.stime = 0;
> +
>  	kvm_clear_async_pf_completion_queue(vcpu);
>  	kvm_async_pf_hash_reset(vcpu);
>  	vcpu->arch.apf.halted = false;
> -- 
> 1.7.3.4
> 
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--
			Gleb.
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