From: Doug Ledford <dledford@redhat.com>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: "Luis R. Rodriguez" <mcgrof@suse.com>,
Andy Lutomirski <luto@amacapital.net>,
mike.marciniszyn@intel.com, infinipath@intel.com,
linux-rdma@vger.kernel.org, awalls@md.metrocast.net,
Toshi Kani <toshi.kani@hp.com>, "H. Peter Anvin" <hpa@zytor.com>,
Ingo Molnar <mingo@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Hal Rosenstock <hal.rosenstock@gmail.com>,
Sean Hefty <sean.hefty@intel.com>,
Suresh Siddha <sbsiddha@gmail.com>,
Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>,
Roland Dreier <roland@purestorage.com>,
Juergen Gross <jgross@suse.com>,
Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
Borislav Petkov <bp@suse.de>, Mel Gorman <mgorman@suse.de>,
Vlastimil Babka <vbabka@suse.cz>,
Davidlohr Bueso <dbueso@suse.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ville Syrj?l? <syrjala@sci.fi>,
Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
linux-media@vger.kernel.org, X86 ML <x86@kernel.org>,
mcgrof@do-not-panic.com
Subject: Re: ioremap_uc() followed by set_memory_wc() - burrying MTRR
Date: Wed, 22 Apr 2015 14:53:11 -0400 [thread overview]
Message-ID: <1429728791.121496.10.camel@redhat.com> (raw)
In-Reply-To: <20150422161755.GA19500@obsidianresearch.com>
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On Wed, 2015-04-22 at 10:17 -0600, Jason Gunthorpe wrote:
> On Wed, Apr 22, 2015 at 05:23:28PM +0200, Luis R. Rodriguez wrote:
> > On Tue, Apr 21, 2015 at 11:39:39PM -0600, Jason Gunthorpe wrote:
> > > On Wed, Apr 22, 2015 at 01:39:07AM +0200, Luis R. Rodriguez wrote:
> > > > > Mike, do you think the time is right to just remove the iPath driver?
> > > >
> > > > With PAT now being default the driver effectively won't work
> > > > with write-combining on modern kernels. Even if systems are old
> > > > they likely had PAT support, when upgrading kernels PAT will work
> > > > but write-combing won't on ipath.
> > >
> > > Sorry, do you mean the driver already doesn't get WC? Or do you mean
> > > after some more pending patches are applied?
> >
> > No, you have to consider the system used and the effects of calls used
> > on the driver in light of this table:
>
> So, just to be clear:
>
> At some point Linux started setting the PAT bits during
> ioremap_nocache, which overrides MTRR, and at that point the driver
> became broken on all PAT capable systems?
>
> Not only that, but we've only just noticed it now, and no user ever
> complained?
>
> So that means either no users exist, or all users are on non-PAT
> systems?
>
> This driver only works on x86-64 systems. Are there any x86-64 systems
> that are not PAT capable? IIRC even the first Opteron had PAT, but my
> memory is fuzzy from back then :|
>
> > Another option in order to enable this type of checks at run time
> > and still be able to build the driver on standard distributions and
> > just prevent if from loading on PAT systems is to have some code in
> > place which would prevent the driver from loading if PAT was
> > enabled, this would enable folks to disable PAT via a kernel command
> > line option, and if that was used then the driver probe would
> > complete.
>
> This seems like a reasonble option to me. At the very least we might
> learn if anyone is still using these cards.
>
> I'd also love to remove the driver if it turns out there are actually
> no users. qib substantially replaces it except for a few very old
> cards.
To be precise, the split is that ipath powers the old HTX bus cards that
only work in AMD systems, qib is all PCI-e cards. I still have a few
HTX cards, but I no longer have any systems with HTX slots, so we
haven't even used this driver in testing for 3 or 4 years now. And
these are all old SDR cards, where the performance numbers were 800MB/s
with WC enabled, 50MB/s without it.
> Mike?
>
> Jason
> --
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> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Doug Ledford <dledford@redhat.com>
GPG KeyID: 0E572FDD
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next prev parent reply other threads:[~2015-04-22 18:54 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-15 20:42 ioremap_uc() followed by set_memory_wc() - burrying MTRR Andy Lutomirski
2015-04-15 20:56 ` H. Peter Anvin
2015-04-15 22:15 ` Luis R. Rodriguez
2015-04-15 22:50 ` Andy Walls
2015-04-15 23:52 ` Andy Lutomirski
2015-04-16 0:33 ` Andy Walls
2015-04-21 22:46 ` Luis R. Rodriguez
2015-04-21 22:57 ` Jason Gunthorpe
2015-04-21 23:39 ` Luis R. Rodriguez
2015-04-22 5:39 ` Jason Gunthorpe
2015-04-22 15:23 ` Luis R. Rodriguez
2015-04-22 15:54 ` Luis R. Rodriguez
2015-04-22 15:59 ` Luis R. Rodriguez
2015-04-22 16:17 ` Jason Gunthorpe
2015-04-22 16:51 ` Luis R. Rodriguez
2015-04-22 18:53 ` Doug Ledford [this message]
2015-04-22 19:05 ` Luis R. Rodriguez
2015-04-22 19:10 ` Doug Ledford
2015-04-22 19:14 ` Luis R. Rodriguez
2015-04-22 20:46 ` Jason Gunthorpe
2015-04-22 20:58 ` Doug Ledford
2015-04-22 16:53 ` Andy Lutomirski
2015-04-22 17:07 ` Luis R. Rodriguez
[not found] <20150410171750.GA5622@wotan.suse.de>
[not found] ` <CALCETrUG=RiG8S9Gpiqm_0CxvxurxLTNKyuyPoFNX46EAauA+g@mail.gmail.com>
[not found] ` <CAB=NE6XgNgu7i2OiDxFVJLWiEjbjBY17-dV7L3yi2+yzgMhEbw@mail.gmail.com>
[not found] ` <1428695379.6646.69.camel@misato.fc.hp.com>
[not found] ` <20150410210538.GB5622@wotan.suse.de>
[not found] ` <1428699490.21794.5.camel@misato.fc.hp.com>
[not found] ` <CALCETrUP688aNjckygqO=AXXrNYvLQX6F0=b5fjmsCqqZU78+Q@mail.gmail.com>
[not found] ` <20150411012938.GC5622@wotan.suse.de>
[not found] ` <CALCETrXd19C6pARde3pv-4pt-i52APtw5xs20itwROPq9VmCfg@mail.gmail.com>
2015-04-13 17:49 ` Luis R. Rodriguez
2015-04-15 22:38 ` Andy Walls
2015-04-15 23:42 ` Andy Lutomirski
2015-04-15 23:59 ` Andy Walls
2015-04-16 0:58 ` Andy Lutomirski
2015-04-16 1:01 ` Andy Walls
2015-04-16 19:19 ` Andy Lutomirski
2015-04-21 17:35 ` Luis R. Rodriguez
2015-04-15 23:58 ` Luis R. Rodriguez
2015-04-16 1:07 ` Andy Walls
2015-04-21 22:02 ` Luis R. Rodriguez
2015-04-21 22:08 ` Luis R. Rodriguez
2015-04-21 22:09 ` Andy Lutomirski
[not found] ` <5536d47a.95968c0a.1d12.ffffbf85@mx.google.com>
2015-04-21 23:14 ` Luis R. Rodriguez
2015-04-16 4:18 ` Hyong-Youb Kim
2015-04-16 18:54 ` Luis R. Rodriguez
2015-04-17 8:00 ` Hyong-Youb Kim
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