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 <ehabkost@xxxxxxxxxx>
> > > ---
> > > 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
> --
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