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

Gleb Natapov
2011-06-14T07:45:00Z

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@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/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.