From: Marcelo Tosatti <mtosatti@redhat.com>
To: Alexander Graf <agraf@suse.de>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, pbonzini@redhat.com
Subject: Re: [PATCH v2] kvmclock: Ensure time in migration never goes backward
Date: Sun, 18 May 2014 10:20:52 -0300 [thread overview]
Message-ID: <20140518132052.GA22484@amt.cnet> (raw)
In-Reply-To: <1400253321-9239-1-git-send-email-agraf@suse.de>
On Fri, May 16, 2014 at 05:15:21PM +0200, Alexander Graf wrote:
> When we migrate we ask the kernel about its current belief on what the guest
> time would be. However, I've seen cases where the kvmclock guest structure
> indicates a time more recent than the kvm returned time.
>
> To make sure we never go backwards, calculate what the guest would have seen
> as time at the point of migration and use that value instead of the kernel
> returned one when it's more recent.
>
> While the underlying bug is supposedly fixed on newer KVM versions, it doesn't
> hurt to base the view of the kvmclock after migration on the same foundation
> in host as well as guest.
Remove this last phrase from the changelog please, the underlying bug is
not fixed on newer KVM versions.
Otherwise
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
WARNING: multiple messages have this Message-ID (diff)
From: Marcelo Tosatti <mtosatti@redhat.com>
To: Alexander Graf <agraf@suse.de>
Cc: pbonzini@redhat.com, qemu-devel@nongnu.org, kvm@vger.kernel.org
Subject: Re: [Qemu-devel] [PATCH v2] kvmclock: Ensure time in migration never goes backward
Date: Sun, 18 May 2014 10:20:52 -0300 [thread overview]
Message-ID: <20140518132052.GA22484@amt.cnet> (raw)
In-Reply-To: <1400253321-9239-1-git-send-email-agraf@suse.de>
On Fri, May 16, 2014 at 05:15:21PM +0200, Alexander Graf wrote:
> When we migrate we ask the kernel about its current belief on what the guest
> time would be. However, I've seen cases where the kvmclock guest structure
> indicates a time more recent than the kvm returned time.
>
> To make sure we never go backwards, calculate what the guest would have seen
> as time at the point of migration and use that value instead of the kernel
> returned one when it's more recent.
>
> While the underlying bug is supposedly fixed on newer KVM versions, it doesn't
> hurt to base the view of the kvmclock after migration on the same foundation
> in host as well as guest.
Remove this last phrase from the changelog please, the underlying bug is
not fixed on newer KVM versions.
Otherwise
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
next prev parent reply other threads:[~2014-05-18 13:21 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-16 15:15 [PATCH v2] kvmclock: Ensure time in migration never goes backward Alexander Graf
2014-05-16 15:15 ` [Qemu-devel] " Alexander Graf
2014-05-18 13:20 ` Marcelo Tosatti [this message]
2014-05-18 13:20 ` Marcelo Tosatti
2014-05-19 11:31 ` Paolo Bonzini
2014-05-19 11:31 ` [Qemu-devel] " Paolo Bonzini
2014-05-21 10:03 ` Alexander Graf
2014-05-21 10:03 ` [Qemu-devel] " Alexander Graf
2014-06-02 20:31 ` Marcin Gibuła
2014-06-03 5:16 ` Marcelo Tosatti
2014-06-03 9:11 ` Marcin Gibuła
2014-06-03 11:13 ` Paolo Bonzini
2014-06-03 16:34 ` [Qemu-devel] [PATCH uq/master] kvmclock: Ensure proper env->tsc value for kvmclock_current_nsec calculation Marcelo Tosatti
2014-07-15 19:45 ` Paolo Bonzini
2014-07-15 20:03 ` Marcin Gibuła
2014-07-15 20:15 ` Paolo Bonzini
2014-07-15 20:31 ` Marcelo Tosatti
2014-07-15 20:34 ` Marcelo Tosatti
2014-07-15 20:43 ` Paolo Bonzini
2014-07-15 21:05 ` Andrey Korolyov
2014-07-15 21:08 ` Paolo Bonzini
2014-07-15 20:43 ` Paolo Bonzini
2014-07-15 19:44 ` [PATCH v2] kvmclock: Ensure time in migration never goes backward Paolo Bonzini
2014-07-15 19:44 ` [Qemu-devel] " Paolo Bonzini
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