From: Jan Kiszka <jan.kiszka@web.de>
To: Zachary Amsden <zamsden@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
Avi Kivity <avi@redhat.com>, kvm <kvm@vger.kernel.org>,
Glauber Costa <glommer@redhat.com>
Subject: Re: [PATCH] fix kvmclock bug
Date: Fri, 24 Sep 2010 09:28:09 +0200 [thread overview]
Message-ID: <4C9C5309.5080403@web.de> (raw)
In-Reply-To: <4C95560D.3050108@redhat.com>
[-- Attachment #1: Type: text/plain, Size: 922 bytes --]
Am 19.09.2010 02:15, Zachary Amsden wrote:
> For CPUs with unstable TSC, we null time offset between not just VCPU
> switches, but all preemptions of the kvm thread. This makes a bug much
> more likely where the kvmclock values are updated before a successful
> exit from virt, causing an underflow.
>
> The null offsetting was added at : bf0fb4a42ba7eb362f4013bd2e93209666793e66
> The underflow happens with this additional patch :
> cf839f5da2b0779b9ec8b990f851fb4e7d681da0
>
> There is a secondary bug, which is that TSC fails to advance with real
> time on unstable TSC, but the fix is much more involved (it requires the
> TSC catchup code).
>
> For now, this patch is sufficient to get things working again for me.
...but not for me. I still face stuck (or infinitely slow) guests that
want to use kvmclock once tsc_unstable gets set. Or is this patch
addressing a different issue?
Jan
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 259 bytes --]
next prev parent reply other threads:[~2010-09-24 7:28 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-19 0:15 [PATCH] fix kvmclock bug Zachary Amsden
2010-09-24 7:28 ` Jan Kiszka [this message]
2010-09-26 9:54 ` Jan Kiszka
2010-09-27 19:00 ` Zachary Amsden
2010-09-28 8:58 ` Jan Kiszka
2010-09-29 8:58 ` Avi Kivity
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4C9C5309.5080403@web.de \
--to=jan.kiszka@web.de \
--cc=avi@redhat.com \
--cc=glommer@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=mtosatti@redhat.com \
--cc=zamsden@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox