From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: [PATCH v3] make tsc stable over migration and machine start Date: Thu, 3 Feb 2011 14:19:53 -0500 Message-ID: <1296760793-14700-1-git-send-email-glommer@redhat.com> Cc: qemu-devel@nongnu.org, avi@redhat.com, mtosatti@redhat.com, Jan Kiszka To: kvm@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:18277 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932406Ab1BCTVc (ORCPT ); Thu, 3 Feb 2011 14:21:32 -0500 Sender: kvm-owner@vger.kernel.org List-ID: If the machine is stopped, we should not record two different tsc values upon a save operation. The same problem happens with kvmclock. But kvmclock is taking a different diretion, being now seen as a separate device. Since this is unlikely to happen with the tsc, I am taking the approach here of simply registering a handler for state change, and using a per-CPUState variable that prevents double updates for the TSC. Signed-off-by: Glauber Costa CC: Jan Kiszka --- v2: updated tsc validation logic, as asked by Jan v3: regenerated against uq/master --- target-i386/cpu.h | 1 + target-i386/kvm.c | 18 +++++++++++++++++- 2 files changed, 18 insertions(+), 1 deletions(-) diff --git a/target-i386/cpu.h b/target-i386/cpu.h index af701a4..5f1df8b 100644 --- a/target-i386/cpu.h +++ b/target-i386/cpu.h @@ -734,6 +734,7 @@ typedef struct CPUX86State { uint32_t sipi_vector; uint32_t cpuid_kvm_features; uint32_t cpuid_svm_features; + bool tsc_valid; /* in order to simplify APIC support, we leave this pointer to the user */ diff --git a/target-i386/kvm.c b/target-i386/kvm.c index 05010bb..ed9557e 100644 --- a/target-i386/kvm.c +++ b/target-i386/kvm.c @@ -301,6 +301,15 @@ void kvm_inject_x86_mce(CPUState *cenv, int bank, uint64_t status, #endif } +static void cpu_update_state(void *opaque, int running, int reason) +{ + CPUState *env = opaque; + + if (running) { + env->tsc_valid = false; + } +} + int kvm_arch_init_vcpu(CPUState *env) { struct { @@ -434,6 +443,8 @@ int kvm_arch_init_vcpu(CPUState *env) } #endif + qemu_add_vm_change_state_handler(cpu_update_state, env); + return kvm_vcpu_ioctl(env, KVM_SET_CPUID2, &cpuid_data); } @@ -1061,7 +1072,12 @@ static int kvm_get_msrs(CPUState *env) if (has_msr_hsave_pa) { msrs[n++].index = MSR_VM_HSAVE_PA; } - msrs[n++].index = MSR_IA32_TSC; + + if (!env->tsc_valid) { + msrs[n++].index = MSR_IA32_TSC; + env->tsc_valid = !vm_running; + } + #ifdef TARGET_X86_64 if (lm_capable_kernel) { msrs[n++].index = MSR_CSTAR; -- 1.7.2.3