From: Aurelien Jarno <aurelien@aurel32.net>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>,
Richard Henderson <rth@twiddle.net>
Subject: Re: [Qemu-devel] [PATCH for-2.5] tcg: Increase the highwater reservation
Date: Tue, 1 Dec 2015 17:34:51 +0100 [thread overview]
Message-ID: <20151201163451.GC9577@aurel32.net> (raw)
In-Reply-To: <CAFEAcA92UH3H8qrm_Re6qN94WvGML18K+c=CV8DvPHH1FSy31g@mail.gmail.com>
On 2015-12-01 16:28, Peter Maydell wrote:
> On 1 December 2015 at 16:19, Richard Henderson <rth@twiddle.net> wrote:
> > If there are a lot of guest memory ops in the TB, the amount of
> > code generated by tcg_out_tb_finalize could be well more than 1k.
> > In the short term, increase the reservation larger than any TB
> > seen in practice.
> >
> > Reported-by: Aurelien Jarno <aurelien@aurel32.net>
> > Signed-off-by: Richard Henderson <rth@twiddle.net>
> > ---
> >
> > Reported and discussed with Aurelien on IRC yesterday. This seems
> > to be the easiest fix for the upcoming release. I will fix this
> > properly (by modifying every backend's finalize routines) for 2.6.
>
> What would be the result of our hitting this bug? I ask because
> there's a report on qemu-discuss about a qemu-i386-on-ARM-host
> bug: http://lists.nongnu.org/archive/html/qemu-discuss/2015-11/msg00042.html
> and the debug log (http://www.mediafire.com/download/ge611be9vbebbw7/qemu.log)
> suggests we're segfaulting in translation on the TB shortly
> after we (successfully) translate a TB whose final 'out' size
> is 1100 and which has 64 guest writes in it. So I'm wondering
> if that's actually the same bug this is fixing...
I don't think this is the same bug. The problem happens because the slow
path of the softmmu load/store access is written at the end of the TB.
In user mode, there is no slow path, so nothing is written at the end.
--
Aurelien Jarno GPG: 4096R/1DDD8C9B
aurelien@aurel32.net http://www.aurel32.net
next prev parent reply other threads:[~2015-12-01 16:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-01 16:19 [Qemu-devel] [PATCH for-2.5] tcg: Increase the highwater reservation Richard Henderson
2015-12-01 16:28 ` Peter Maydell
2015-12-01 16:34 ` Aurelien Jarno [this message]
2015-12-01 16:40 ` Aurelien Jarno
2015-12-01 23:06 ` Richard Henderson
2015-12-01 23:20 ` Peter Maydell
2015-12-01 16:46 ` Richard Henderson
2015-12-01 16:32 ` Aurelien Jarno
2015-12-02 18:36 ` Richard Henderson
2015-12-03 12:19 ` Aurelien Jarno
2015-12-04 8:36 ` Aurelien Jarno
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=20151201163451.GC9577@aurel32.net \
--to=aurelien@aurel32.net \
--cc=peter.maydell@linaro.org \
--cc=qemu-devel@nongnu.org \
--cc=rth@twiddle.net \
/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;
as well as URLs for NNTP newsgroup(s).