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 11:45:36 -0200 Message-ID: <20170104134534.GA21361@amt.cnet> References: <1482866480-26208-1-git-send-email-ehabkost@redhat.com> <1482866480-26208-3-git-send-email-ehabkost@redhat.com> <20170104114404.GA14961@amt.cnet> <20170104134017.GH3315@thinpad.lan.raisama.net> 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]:38884 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967164AbdADNpy (ORCPT ); Wed, 4 Jan 2017 08:45:54 -0500 Content-Disposition: inline In-Reply-To: <20170104134017.GH3315@thinpad.lan.raisama.net> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Jan 04, 2017 at 11:40:17AM -0200, Eduardo Habkost wrote: > On Wed, Jan 04, 2017 at 09:44:06AM -0200, Marcelo Tosatti wrote: > > 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 > > This is invalid usage. Management software is responsible for > keeping the same configuration on source and destination. Fine. Just to confirm: you do not expect libvirt to use -cpu XXX,tsc-frequency=ZZZZZ On both source and destination, correct? > > 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 > > -- > Eduardo > -- > 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