From: Toshi Kani <toshi.kani@hpe.com>
To: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Borislav Petkov <bp@suse.de>,
Richard Purdie <richard.purdie@linuxfoundation.org>,
Toshi Kani <toshi.kani@hp.com>,
Bruce Ashfield <bruce.ashfield@windriver.com>,
"Hart, Darren" <darren.hart@intel.com>,
"saul.wold" <saul.wold@intel.com>,
linux-kernel@vger.kernel.org
Subject: Re: runtime regression with "x86/mm/pat: Emulate PAT when it is disabled"
Date: Mon, 07 Mar 2016 18:35:13 -0700 [thread overview]
Message-ID: <1457400913.15454.435.camel@hpe.com> (raw)
In-Reply-To: <1457398578.15454.421.camel@hpe.com>
On Mon, 2016-03-07 at 17:56 -0700, Toshi Kani wrote:
> On Mon, 2016-03-07 at 18:53 -0500, Paul Gortmaker wrote:
> > [Re: runtime regression with "x86/mm/pat: Emulate PAT when it is
> > disabled"] On 07/03/2016 (Mon 16:38) Toshi Kani wrote:
> >
> > > On Mon, 2016-03-07 at 16:08 -0500, Paul Gortmaker wrote:
> > > > [dropping oe list and lkml since attaching dmesg files.]
> > > >
> >
> > [...]
> >
> > > > > Yes, please send me full dmesg files. Since I do not know your
> > > > > original state, the diff does not give me the whole picture.
> > > >
> > > > Attached.
> > >
> > > Thanks for the dmesg files! As I suspected, there is no message from
> > > pat_init() in both cases. That is, you are missing the following
> > > message,
> > > which shows how PAT is configured to support cache attributes.
> > >
> > > # dmesg | grep PAT
> > > [0.000000] x86/PAT: Configuration [0-7]: WB WC UC- UC WB WC UC-
> > > WT
> >
> > Interesting...
> >
> > >
> > > It may have seemed working before, but you did not have WC configured
> > > to PAT without calling pat_init(). There was not a proper check in
> > > place to detect this error before. Can you please check your code to
> > > see what caused this skip of pat_init()? If you have a git tree, I
> > > can
> > > take a look as well.
> >
> > You already have git copies of what I'm running, since it is vanilla
> > mainline commits. No code changes at this end whatsoever. I did the
> > bisect on vanilla mainline. All I took from yocto was their ".config"
> >
> > To recap, v4.1-rc5-21-g9dac62909451 works, v4.1-rc5-22-g9cd25aac1f44
> > fails, and v4.5-rc6 also fails. If pat_init() isn't called then this
> > is a bug in current mainline. I'll have a look later myself and see
> > if I can trace out how we expect to get to pat_init() and how that
> > might be skipped inadvertently unless someone beats me to it.
>
> Oh, I see. Can you send me the ".config" file?
And also an output of /proc/cpuinfo, please?
I think I know what's going on. I noticed that you have the following
message in your dmesg files.
[ 0.000000] MTRR: Disabled
MTRR is set to disabled when your CPU is Intel but does not support MTRR.
Perhaps, QEMU does not emulate MTRR?
pat_init() is not called when MTRR is disabled. I think this dependency is
wrong, and it needs to be fixed.
This issue has been there for a long time, and you have been running
essentially as PAT disabled in the past. The commit in question simply
detected this issue.
Thanks,
-Toshi
next prev parent reply other threads:[~2016-03-08 0:42 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-03 20:59 runtime regression with "x86/mm/pat: Emulate PAT when it is disabled" Paul Gortmaker
2016-03-03 21:18 ` Paul Gortmaker
2016-03-04 5:02 ` Toshi Kani
2016-03-04 18:37 ` Paul Gortmaker
2016-03-04 22:12 ` Toshi Kani
2016-03-07 0:35 ` Paul Gortmaker
2016-03-07 16:03 ` Toshi Kani
[not found] ` <20160307210852.GC26051@windriver.com>
2016-03-07 23:38 ` Toshi Kani
2016-03-07 23:53 ` Paul Gortmaker
2016-03-08 0:56 ` Toshi Kani
2016-03-08 1:35 ` Toshi Kani [this message]
2016-03-08 3:28 ` Paul Gortmaker
2016-03-08 16:38 ` Toshi Kani
2016-03-10 14:42 ` Paul Gortmaker
2016-03-10 16:49 ` Toshi Kani
2016-03-10 17:20 ` Borislav Petkov
2016-03-10 19:04 ` Paul Gortmaker
2016-03-10 19:19 ` Borislav Petkov
2016-03-11 13:23 ` One Thousand Gnomes
2016-03-11 13:40 ` Borislav Petkov
2016-03-11 19:18 ` Paolo Bonzini
2016-03-11 22:16 ` Borislav Petkov
2016-03-11 22:28 ` Bruce Ashfield
2016-03-11 23:29 ` Richard Purdie
2016-03-12 12:03 ` Borislav Petkov
2016-03-10 20:12 ` Toshi Kani
2016-03-10 20:04 ` Toshi Kani
2016-03-10 19:20 ` Borislav Petkov
2016-03-10 20:24 ` Toshi Kani
2016-03-10 21:07 ` Borislav Petkov
2016-03-10 23:17 ` Toshi Kani
2016-03-08 3:16 ` Paul Gortmaker
2016-03-08 16:13 ` Toshi Kani
2016-03-08 16:03 ` Paul Gortmaker
2016-03-08 17:01 ` Toshi Kani
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=1457400913.15454.435.camel@hpe.com \
--to=toshi.kani@hpe.com \
--cc=bp@suse.de \
--cc=bruce.ashfield@windriver.com \
--cc=darren.hart@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=paul.gortmaker@windriver.com \
--cc=richard.purdie@linuxfoundation.org \
--cc=saul.wold@intel.com \
--cc=toshi.kani@hp.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;
as well as URLs for NNTP newsgroup(s).