From: Dave Airlie <airlied@gmail.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Henrique de Moraes Holschuh <hmh@hmh.eng.br>,
Brice Goglin <brice.goglin@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
David Airlie <airlied@linux.ie>,
dri-devel@lists.freedesktop.org,
Andy Lutomirski <luto@amacapital.net>
Subject: Re: MTRR use in drivers
Date: Mon, 24 Jun 2013 06:30:05 +1000 [thread overview]
Message-ID: <CAPM=9tzkJTf4d=HfBUs3VwmNG1+Zo5J-JURYd4mYcJ82yXZOKg@mail.gmail.com> (raw)
In-Reply-To: <51C75465.9060007@zytor.com>
>>> Why do you care about performance when PAT is disabled?
breaking old boxes just because, is just going to get reverted when I
get the first regression report that you broke old boxes.
Andy Lutomirski just submitted a bunch of patches to clean up the DRM
usage of mtrrs, they are in drm-next, afaik we no longer add them on
PAT systems.
Dave.
>>
>> It will regress already slow boxes. We blacklist a LOT of P4s, PMs, etc and
>> nobody ever took the pain to track down which ones of those actually have
>> PAT+MTRR aliasing bugs.
>>
>> These boxes have boards like the Radeon X300, which needs either PAT or MTRR
>> to not become unusable...
>>
>
> We're talking hardware which is now many years old, but this is causing
> very serious problems on real, modern hardware. As far as I understand
> it, too, the blacklisting was precautionary (the only bug that I
> personally know about is a performance bug, where WC would be
> incorrectly converted to UC.)
>
> We need a way forward here. If it is the only way I think we would have
> to sacrifice the old machines, but perhaps something can be worked out
> (e.g. if PAT is disabled, fall back to MTRRs if available for ioremap_wc()).
>
> -hpa
>
> --
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next prev parent reply other threads:[~2013-06-23 20:30 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-21 5:00 MTRR use in drivers H. Peter Anvin
2013-06-23 6:35 ` Brice Goglin
2013-06-23 14:07 ` H. Peter Anvin
2013-06-23 19:29 ` Henrique de Moraes Holschuh
2013-06-23 20:02 ` H. Peter Anvin
2013-06-23 20:30 ` Dave Airlie [this message]
2013-06-23 20:38 ` H. Peter Anvin
2013-06-23 20:54 ` Dave Airlie
2013-06-23 20:58 ` H. Peter Anvin
2013-06-23 21:27 ` Dave Airlie
2013-06-23 23:09 ` Andy Lutomirski
2013-06-23 21:56 ` Henrique de Moraes Holschuh
2013-06-23 22:10 ` H. Peter Anvin
2013-06-24 0:02 ` Henrique de Moraes Holschuh
2013-06-24 0:31 ` H. Peter Anvin
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