From: malc <av1474@comtv.ru>
To: Fabien Chouteau <chouteau@adacore.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] Multiple instances of Qemu on Windows multicore
Date: Wed, 2 Nov 2011 21:16:50 +0400 (MSK) [thread overview]
Message-ID: <alpine.LNX.2.00.1111022115290.2177@linmac> (raw)
In-Reply-To: <4EB1796B.7050901@adacore.com>
On Wed, 2 Nov 2011, Fabien Chouteau wrote:
> On 02/11/2011 17:25, Paolo Bonzini wrote:
> > On 11/02/2011 04:38 PM, Fabien Chouteau wrote:
> >> Hello fellow Qemu aficionados,
> >>
> >> On Windows, Qemu sets the affinity mask in order to run all thread on
> >> CPU0, with this comment in the code (os-win32.c:182):
> >>
> >> /* Note: cpu_interrupt() is currently not SMP safe, so we force
> >> QEMU to run on a single CPU */
> >>
> >> This was added by Fabrice Bellard in 2006 (git show a8e5ac33d).
> >>
> >> I can't find/understand any reason for this CPU affinity restriction.
> >
> > Have you tried looking for a justification in the mailing lists?
>
> Yes, and I found few mails from Fabrice Bellard and Konrad Schwarz in
> the archives:
>
> http://thread.gmane.org/gmane.comp.emulators.qemu/13804
>
> and
>
> http://thread.gmane.org/gmane.comp.emulators.qemu/13831/focus=13805
>
> But it didn't provide more information about the problem.
>
> >
> > Also, I suppose you have tested without the affinity mask and it works?
> >
>
> Yes I did, it works pretty well. I had 1 unexpected failure among ~6000
> tests. But I would like to have a substantial explanation.
>
> >
> > Offhand I cannot think of why that would be needed.
> >
>
> OK, thanks for your help.
(mm)Timers have a possibility of running on a thread of their own which
might be schedulled on the CPU different from the thread that runs
emulated code, unchaining TBs and can (and will) fail in this case.
--
mailto:av1474@comtv.ru
next prev parent reply other threads:[~2011-11-02 17:16 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-02 15:38 [Qemu-devel] Multiple instances of Qemu on Windows multicore Fabien Chouteau
2011-11-02 16:25 ` Paolo Bonzini
2011-11-02 17:10 ` Fabien Chouteau
2011-11-02 17:16 ` malc [this message]
2011-11-02 17:45 ` Paolo Bonzini
2011-11-02 17:55 ` malc
2011-11-02 18:01 ` Peter Maydell
2011-11-02 19:52 ` Paolo Bonzini
2011-11-02 19:57 ` Peter Maydell
2011-11-03 9:56 ` Fabien Chouteau
2011-11-03 9:54 ` Fabien Chouteau
2011-11-03 10:10 ` Paolo Bonzini
2011-11-03 10:29 ` Avi Kivity
2011-11-03 11:50 ` Paolo Bonzini
2011-11-04 9:27 ` Fabien Chouteau
2011-11-04 9:34 ` Paolo Bonzini
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