From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [PATCH 2/4] kvm: Allow invtsc migration if tsc-khz is set explicitly Date: Wed, 4 Jan 2017 09:44:06 -0200 Message-ID: <20170104114404.GA14961@amt.cnet> References: <1482866480-26208-1-git-send-email-ehabkost@redhat.com> <1482866480-26208-3-git-send-email-ehabkost@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: qemu-devel@nongnu.org, Paolo Bonzini , kvm@vger.kernel.org, Haozhong Zhang To: Eduardo Habkost Return-path: Received: from mx1.redhat.com ([209.132.183.28]:57070 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751267AbdADLqB (ORCPT ); Wed, 4 Jan 2017 06:46:01 -0500 Content-Disposition: inline In-Reply-To: <1482866480-26208-3-git-send-email-ehabkost@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Dec 27, 2016 at 05:21:18PM -0200, Eduardo Habkost wrote: > We can safely allow a VM to be migrated with invtsc enabled if > tsc-khz is set explicitly, because QEMU already refuses to start > if it can't set the TSC frequency to the configured value. On the source host, yes, but on the destination it does not. SOURCE: -cpu kvm64,tsc-frequency=2660001000 DESTINATION: -cpu kvm64 Only prints: qemu-system-x86_64: warning: TSC frequency mismatch between VM (2660001 kHz) and host (2893428 kHz), and TSC scaling unavailable qemu-system-x86_64: warning: TSC frequency mismatch between VM (2660001 kHz) and host (2893428 kHz), and TSC scaling unavailable And allows migration. > Signed-off-by: Eduardo Habkost > --- > target/i386/kvm.c | 19 ++++++++++--------- > 1 file changed, 10 insertions(+), 9 deletions(-) > > diff --git a/target/i386/kvm.c b/target/i386/kvm.c > index a26290f..6a51399 100644 > --- a/target/i386/kvm.c > +++ b/target/i386/kvm.c > @@ -962,15 +962,16 @@ int kvm_arch_init_vcpu(CPUState *cs) > has_msr_mcg_ext_ctl = has_msr_feature_control = true; > } > > - if ((env->features[FEAT_8000_0007_EDX] & CPUID_APM_INVTSC) && > - invtsc_mig_blocker == NULL) { > - /* for migration */ > - error_setg(&invtsc_mig_blocker, > - "State blocked by non-migratable CPU device" > - " (invtsc flag)"); > - migrate_add_blocker(invtsc_mig_blocker); > - /* for savevm */ > - vmstate_x86_cpu.unmigratable = 1; > + if (!env->user_tsc_khz) { > + if ((env->features[FEAT_8000_0007_EDX] & CPUID_APM_INVTSC) && > + invtsc_mig_blocker == NULL) { > + /* for migration */ > + error_setg(&invtsc_mig_blocker, > + "State blocked by non-migratable CPU device" > + " (invtsc flag)"); > + migrate_add_blocker(invtsc_mig_blocker); > + /* for savevm */ > + vmstate_x86_cpu.unmigratable = 1; > } > > cpuid_data.cpuid.padding = 0; > -- > 2.7.4