Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752643Ab0HTIMs (ORCPT ); Fri, 20 Aug 2010 04:12:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52948 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751501Ab0HTIJD (ORCPT ); Fri, 20 Aug 2010 04:09:03 -0400 From: Zachary Amsden To: kvm@vger.kernel.org Cc: Zachary Amsden , Avi Kivity , Marcelo Tosatti , Glauber Costa , Thomas Gleixner , John Stultz , linux-kernel@vger.kernel.org Subject: [KVM timekeeping 25/35] Add clock catchup mode Date: Thu, 19 Aug 2010 22:07:39 -1000 Message-Id: <1282291669-25709-26-git-send-email-zamsden@redhat.com> In-Reply-To: <1282291669-25709-1-git-send-email-zamsden@redhat.com> References: <1282291669-25709-1-git-send-email-zamsden@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5346 Lines: 173 Make the clock update handler handle generic clock synchronization, not just KVM clock. We add a catchup mode which keeps passthrough TSC in line with absolute guest TSC. Signed-off-by: Zachary Amsden --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/x86.c | 55 ++++++++++++++++++++++++++------------ 2 files changed, 38 insertions(+), 18 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3a54cc1..ec1dc3a 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -343,6 +343,7 @@ struct kvm_vcpu_arch { u64 last_kernel_ns; u64 last_tsc_nsec; u64 last_tsc_write; + bool tsc_rebase; bool nmi_pending; bool nmi_injected; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ac0b2d9..a4215d7 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -927,6 +927,15 @@ static void kvm_arch_set_tsc_khz(struct kvm *kvm, u32 this_tsc_khz) kvm->arch.virtual_tsc_khz = this_tsc_khz; } +static u64 compute_guest_tsc(struct kvm_vcpu *vcpu, s64 kernel_ns) +{ + u64 tsc = pvclock_scale_delta(kernel_ns-vcpu->arch.last_tsc_nsec, + vcpu->kvm->arch.virtual_tsc_mult, + vcpu->kvm->arch.virtual_tsc_shift); + tsc += vcpu->arch.last_tsc_write; + return tsc; +} + void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data) { struct kvm *kvm = vcpu->kvm; @@ -984,22 +993,29 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) unsigned long this_tsc_khz; s64 kernel_ns, max_kernel_ns; u64 tsc_timestamp; - - if ((!vcpu->time_page)) - return 0; + bool catchup = (!vcpu->time_page); /* Keep irq disabled to prevent changes to the clock */ local_irq_save(flags); kvm_get_msr(v, MSR_IA32_TSC, &tsc_timestamp); kernel_ns = getnsboottime(); this_tsc_khz = __get_cpu_var(cpu_tsc_khz); - local_irq_restore(flags); if (unlikely(this_tsc_khz == 0)) { + local_irq_restore(flags); kvm_make_request(KVM_REQ_CLOCK_UPDATE, v); return 1; } + if (catchup) { + u64 tsc = compute_guest_tsc(v, kernel_ns); + if (tsc > tsc_timestamp) + kvm_x86_ops->adjust_tsc_offset(v, tsc-tsc_timestamp); + } + local_irq_restore(flags); + if (catchup) + return 0; + /* * Time as measured by the TSC may go backwards when resetting the base * tsc_timestamp. The reason for this is that the TSC resolution is @@ -1065,14 +1081,9 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) return 0; } -static int kvm_request_guest_time_update(struct kvm_vcpu *v) +static void kvm_request_clock_update(struct kvm_vcpu *v) { - struct kvm_vcpu_arch *vcpu = &v->arch; - - if (!vcpu->time_page) - return 0; kvm_make_request(KVM_REQ_CLOCK_UPDATE, v); - return 1; } static bool msr_mtrr_valid(unsigned msr) @@ -1398,6 +1409,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) } vcpu->arch.time = data; + kvm_request_clock_update(vcpu); /* we verify if the enable bit is set... */ if (!(data & 1)) @@ -1413,8 +1425,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) kvm_release_page_clean(vcpu->arch.time_page); vcpu->arch.time_page = NULL; } - - kvm_request_guest_time_update(vcpu); break; } case MSR_IA32_MCG_CTL: @@ -1929,16 +1939,20 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) } kvm_x86_ops->vcpu_load(vcpu, cpu); - if (unlikely(vcpu->cpu != cpu) || check_tsc_unstable()) { + if (unlikely(vcpu->cpu != cpu) || vcpu->arch.tsc_rebase) { /* Make sure TSC doesn't go backwards */ s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 : native_read_tsc() - vcpu->arch.last_host_tsc; if (tsc_delta < 0) mark_tsc_unstable("KVM discovered backwards TSC"); - if (check_tsc_unstable()) + if (check_tsc_unstable()) { kvm_x86_ops->adjust_tsc_offset(vcpu, -tsc_delta); - kvm_migrate_timers(vcpu); + kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu); + } + if (vcpu->cpu != cpu) + kvm_migrate_timers(vcpu); vcpu->cpu = cpu; + vcpu->arch.tsc_rebase = 0; } } @@ -1947,6 +1961,12 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) kvm_x86_ops->vcpu_put(vcpu); kvm_put_guest_fpu(vcpu); vcpu->arch.last_host_tsc = native_read_tsc(); + + /* For unstable TSC, force compensation and catchup on next CPU */ + if (check_tsc_unstable()) { + vcpu->arch.tsc_rebase = 1; + kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu); + } } static int is_efer_nx(void) @@ -4307,8 +4327,7 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va kvm_for_each_vcpu(i, vcpu, kvm) { if (vcpu->cpu != freq->cpu) continue; - if (!kvm_request_guest_time_update(vcpu)) - continue; + kvm_request_clock_update(vcpu); if (vcpu->cpu != smp_processor_id()) send_ipi = 1; } @@ -5597,7 +5616,7 @@ int kvm_arch_hardware_enable(void *garbage) list_for_each_entry(kvm, &vm_list, vm_list) kvm_for_each_vcpu(i, vcpu, kvm) if (vcpu->cpu == smp_processor_id()) - kvm_request_guest_time_update(vcpu); + kvm_request_clock_update(vcpu); return kvm_x86_ops->hardware_enable(garbage); } -- 1.7.1 -- 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/