Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756042Ab3FLHnv (ORCPT ); Wed, 12 Jun 2013 03:43:51 -0400 Received: from mail9.hitachi.co.jp ([133.145.228.44]:35353 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755886Ab3FLHns (ORCPT ); Wed, 12 Jun 2013 03:43:48 -0400 X-AuditID: 85900ec0-d1ac5b900000151e-5c-51b826b1747a Subject: [PATCH V3 1/1] kvm: Add a tracepoint write_tsc_offset To: Marcelo Tosatti , linux-kernel@vger.kernel.org, Gleb Natapov From: Yoshihiro YUNOMAE Cc: David Sharp , yrl.pp-manager.tt@hitachi.com, Steven Rostedt , Hidehiro Kawai , Ingo Molnar , "H. Peter Anvin" , Masami Hiramatsu , Thomas Gleixner , Joerg Roedel Date: Wed, 12 Jun 2013 16:43:44 +0900 Message-ID: <20130612074344.25553.97827.stgit@yunodevel> In-Reply-To: <20130612074341.25553.56877.stgit@yunodevel> References: <20130612074341.25553.56877.stgit@yunodevel> User-Agent: StGit/0.16 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5733 Lines: 152 Add a tracepoint write_tsc_offset for tracing TSC offset change. We want to merge ftrace's trace data of guest OSs and the host OS using TSC for timestamp in chronological order. We need "TSC offset" values for each guest when merge those because the TSC value on a guest is always the host TSC plus guest's TSC offset. If we get the TSC offset values, we can calculate the host TSC value for each guest events from the TSC offset and the event TSC value. The host TSC values of the guest events are used when we want to merge trace data of guests and the host in chronological order. (Note: the trace_clock of both the host and the guest must be set x86-tsc in this case) This tracepoint also records vcpu_id which can be used to merge trace data for SMP guests. A merge tool will read TSC offset for each vcpu, then the tool converts guest TSC values to host TSC values for each vcpu. TSC offset is stored in the VMCS by vmx_write_tsc_offset() or vmx_adjust_tsc_offset(). KVM executes the former function when a guest boots. The latter function is executed when kvm clock is updated. Only host can read TSC offset value from VMCS, so a host needs to output TSC offset value when TSC offset is changed. Since the TSC offset is not often changed, it could be overwritten by other frequent events while tracing. To avoid that, I recommend to use a special instance for getting this event: 1. set a instance before booting a guest # cd /sys/kernel/debug/tracing/instances # mkdir tsc_offset # cd tsc_offset # echo x86-tsc > trace_clock # echo 1 > events/kvm/kvm_write_tsc_offset/enable 2. boot a guest Signed-off-by: Yoshihiro YUNOMAE Cc: Joerg Roedel Cc: Marcelo Tosatti Cc: Gleb Natapov Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" --- arch/x86/kvm/svm.c | 10 +++++++++- arch/x86/kvm/trace.h | 21 +++++++++++++++++++++ arch/x86/kvm/vmx.c | 7 ++++++- arch/x86/kvm/x86.c | 1 + 4 files changed, 37 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index a14a6ea..c0bc803 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1026,7 +1026,10 @@ static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset) g_tsc_offset = svm->vmcb->control.tsc_offset - svm->nested.hsave->control.tsc_offset; svm->nested.hsave->control.tsc_offset = offset; - } + } else + trace_kvm_write_tsc_offset(vcpu->vcpu_id, + svm->vmcb->control.tsc_offset, + offset); svm->vmcb->control.tsc_offset = offset + g_tsc_offset; @@ -1044,6 +1047,11 @@ static void svm_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment, bool ho svm->vmcb->control.tsc_offset += adjustment; if (is_guest_mode(vcpu)) svm->nested.hsave->control.tsc_offset += adjustment; + else + trace_kvm_write_tsc_offset(vcpu->vcpu_id, + svm->vmcb->control.tsc_offset - adjustment, + svm->vmcb->control.tsc_offset); + mark_dirty(svm->vmcb, VMCB_INTERCEPTS); } diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h index fe5e00e..6c82cf1 100644 --- a/arch/x86/kvm/trace.h +++ b/arch/x86/kvm/trace.h @@ -815,6 +815,27 @@ TRACE_EVENT(kvm_track_tsc, __print_symbolic(__entry->host_clock, host_clocks)) ); +TRACE_EVENT(kvm_write_tsc_offset, + TP_PROTO(unsigned int vcpu_id, __u64 previous_tsc_offset, + __u64 next_tsc_offset), + TP_ARGS(vcpu_id, previous_tsc_offset, next_tsc_offset), + + TP_STRUCT__entry( + __field( unsigned int, vcpu_id ) + __field( __u64, previous_tsc_offset ) + __field( __u64, next_tsc_offset ) + ), + + TP_fast_assign( + __entry->vcpu_id = vcpu_id; + __entry->previous_tsc_offset = previous_tsc_offset; + __entry->next_tsc_offset = next_tsc_offset; + ), + + TP_printk("vcpu=%u prev=%llu next=%llu", __entry->vcpu_id, + __entry->previous_tsc_offset, __entry->next_tsc_offset) +); + #endif /* CONFIG_X86_64 */ #endif /* _TRACE_KVM_H */ diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 25a791e..eb11856 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2096,6 +2096,8 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset) (nested_cpu_has(vmcs12, CPU_BASED_USE_TSC_OFFSETING) ? vmcs12->tsc_offset : 0)); } else { + trace_kvm_write_tsc_offset(vcpu->vcpu_id, + vmcs_read64(TSC_OFFSET), offset); vmcs_write64(TSC_OFFSET, offset); } } @@ -2103,11 +2105,14 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset) static void vmx_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment, bool host) { u64 offset = vmcs_read64(TSC_OFFSET); + vmcs_write64(TSC_OFFSET, offset + adjustment); if (is_guest_mode(vcpu)) { /* Even when running L2, the adjustment needs to apply to L1 */ to_vmx(vcpu)->nested.vmcs01_tsc_offset += adjustment; - } + } else + trace_kvm_write_tsc_offset(vcpu->vcpu_id, offset, + offset + adjustment); } static u64 vmx_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 05a8b1a..c942a0c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7264,3 +7264,4 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_intr_vmexit); EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_invlpga); EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_skinit); EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_intercepts); +EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_write_tsc_offset); -- 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/