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    SubjectRe: [PATCH 3/7] KVM-HV: KVM Steal time implementation
    On Wed, Jun 15, 2011 at 12:09:31AM -0300, Glauber Costa wrote:
    > On 06/14/2011 04:45 AM, Gleb Natapov wrote:
    > >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?
    >
    > Actually, I'd expect most read/writes to benefit from caching, no?
    > So why don't we just rename kvm_write_guest_cached() to
    > kvm_write_guest(), and the few places - if any - that need to force
    > transversing of the gfn mappings, get renamed to
    > kvm_write_guest_uncached ?
    >
    Good idea. I do not see any places where kvm_write_guest_uncached is
    needed from a brief look. Avi?

    > >>+ &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.
    > Sorry, missed that the first time I've read your e-mail.
    >
    > If done like you said, time spent on the hypervisor is accounted as
    > steal time. I don't think it is.
    I thought that this is the point of a steal time. Running other
    tasks/guests is a hypervisor overhead too after all :) Also what about
    time spend serving host interrupts between put/get? It will not be
    accounted as steal time, correct?

    >
    > Steal time is time spent running someone else's job instead of
    > yours. The name for the time spent in the hypervisor doing something
    > for *you* is just overhead.
    OK. That is the question of a definition I guess. If you define it like
    that the code is correct.

    >
    > >
    > >> 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
    > >>
    > >>--
    > >>To unsubscribe from this list: send the line "unsubscribe kvm" in
    > >>the body of a message to majordomo@vger.kernel.org
    > >>More majordomo info at http://vger.kernel.org/majordomo-info.html
    > >
    > >--
    > > Gleb.

    --
    Gleb.


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