From: Paolo Bonzini <pbonzini@redhat.com>
To: Eduardo Habkost <ehabkost@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
kvm@vger.kernel.org, qemu-devel@nongnu.org,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Juan Quintela <quintela@redhat.com>,
Radim Krcmar <rkrcmar@redhat.com>
Subject: Re: [qemu patch 2/2] kvmclock: reduce kvmclock difference on migration
Date: Mon, 28 Nov 2016 16:12:55 +0100 [thread overview]
Message-ID: <44a6702d-e91e-2815-1e2e-aef67d750b9e@redhat.com> (raw)
In-Reply-To: <20161128142855.GC14328@thinpad.lan.raisama.net>
On 28/11/2016 15:28, Eduardo Habkost wrote:
> > + s->src_use_reliable_get_clock = data.flags & KVM_CLOCK_TSC_STABLE;
>
> I still don't understand the reasoning behind
> kvm_has_adjust_clock_stable() vs (flags & KVM_CLOCK_TSC_STABLE),
> but on either case, updating src_use_reliable_get_clock inside
> kvm_get_clock() looks like the right thing to do.
There are three possibility: the kernel tells you the clock is stable,
the kernel tells you the clock is unstable, the kernel is too old and
doesn't tell you anything. Then:
kvm_has_adjust_clock_stable() == true:
if the clock is stable, KVM_CLOCK_TSC_STABLE will be set in "flags"
if the clock is unstable, KVM_CLOCK_TSC_STABLE will be unset
kvm_has_adjust_clock_stable() == false:
you cannot know if the clock is stable
Paolo
next prev parent reply other threads:[~2016-11-28 15:12 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-14 12:36 [qemu patch 0/2] improve kvmclock difference on migration Marcelo Tosatti
2016-11-14 12:36 ` [qemu patch 1/2] kvm: sync linux headers Marcelo Tosatti
2016-11-14 12:36 ` [qemu patch 2/2] kvmclock: reduce kvmclock difference on migration Marcelo Tosatti
2016-11-14 13:54 ` Paolo Bonzini
2016-11-14 14:00 ` Marcelo Tosatti
2016-11-14 14:22 ` Paolo Bonzini
2016-11-14 14:50 ` Marcelo Tosatti
2016-11-14 15:00 ` Paolo Bonzini
2016-11-14 15:40 ` Marcelo Tosatti
2016-11-14 16:43 ` Paolo Bonzini
2016-11-14 17:13 ` Marcelo Tosatti
2016-11-14 17:20 ` Paolo Bonzini
2016-11-14 18:15 ` Marcelo Tosatti
2016-11-17 12:16 ` Marcelo Tosatti
2016-11-17 13:03 ` Paolo Bonzini
2016-11-28 13:47 ` Paolo Bonzini
2016-11-28 14:28 ` Eduardo Habkost
2016-11-28 15:12 ` Paolo Bonzini [this message]
2016-11-28 16:36 ` Marcelo Tosatti
2016-11-28 17:30 ` Paolo Bonzini
2016-11-14 14:11 ` Juan Quintela
2016-11-14 14:09 ` Juan Quintela
2016-11-14 15:37 ` Marcelo Tosatti
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