Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757764Ab1FPMV5 (ORCPT ); Thu, 16 Jun 2011 08:21:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34919 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757231Ab1FPMVz (ORCPT ); Thu, 16 Jun 2011 08:21:55 -0400 Date: Thu, 16 Jun 2011 15:21:46 +0300 From: Gleb Natapov To: Glauber Costa Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Rik van Riel , Jeremy Fitzhardinge , Peter Zijlstra , Avi Kivity , Anthony Liguori , Eric B Munson Subject: Re: [PATCH 3/7] KVM-HV: KVM Steal time implementation Message-ID: <20110616122146.GT491@redhat.com> References: <1308007897-17013-1-git-send-email-glommer@redhat.com> <1308007897-17013-4-git-send-email-glommer@redhat.com> <20110614074500.GM491@redhat.com> <4DF8226B.20408@redhat.com> <20110615090951.GQ491@redhat.com> <4DF978F6.3040002@redhat.com> <20110616112723.GS491@redhat.com> <4DF9F2FE.5000304@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4DF9F2FE.5000304@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 11338 Lines: 284 On Thu, Jun 16, 2011 at 09:11:42AM -0300, Glauber Costa wrote: > On 06/16/2011 08:27 AM, Gleb Natapov wrote: > >On Thu, Jun 16, 2011 at 12:31:02AM -0300, Glauber Costa wrote: > >>On 06/15/2011 06:09 AM, Gleb Natapov wrote: > >>>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 > >>>>>>CC: Rik van Riel > >>>>>>CC: Jeremy Fitzhardinge > >>>>>>CC: Peter Zijlstra > >>>>>>CC: Avi Kivity > >>>>>>CC: Anthony Liguori > >>>>>>CC: Eric B Munson > >>>>>>--- > >>>>>> 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? > >> > >>This is mostly semantics. I like to compare this to a normal > >>process: There is a difference between time the OS spent on your > >>behalf, doing your system calls (sys), and time spent by other > >>processes. Similar thing here. > >> > >The problem with this approach is that things like doing "info cpus" > >in qemu monitor will change guest scheduling behaviour. Do we want it > >to be like that? > > You mean because it is running in a different thread, and will > compete for resources with the cpu thread ? > No, because it executes GET_REGS ioctl (in vcpu thread). The time it takes to execute it is accounted as time the hypervior spent on behave of a guest. Not a big deal if it is executed rarely. I tend to use "info cpus"/"info register" quite a lot when debugging and would preffer it to not affect guest behaviour. > >>Which put/get are you referring to specifically ? You mean > >>vcpu_put() vs vcpu_load() ? > >> > >Yes. > > > >>If they are after vcpu_put(), they will, because at this time your > >>process is officially out of the cpu. > >> > >And if they are between vcpu_load() and vcpu_put() they will be accounted as > >a work done on behalf of a guest although they are likely unrelated. > I think the best we can do around it here is record steal time / > measure time as late as we can. We could in theory subtract irq > time, but it sounds too complicated for little gain. > Recording steal time/measure time as close as possible to vmentry/vmexit is what I propose :) I agree about little gain part. > >> > >>>> > >>>>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. > > > >-- > > Gleb. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/