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From: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Chris Bainbridge <chris.bainbridge@gmail.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: set Pentium M as PAE capable
Date: Tue, 25 Feb 2014 12:07:43 +0000	[thread overview]
Message-ID: <20140225120743.6ed967ed@alan.etchedpixels.co.uk> (raw)
In-Reply-To: <530C7465.2080600@zytor.com>

On Tue, 25 Feb 2014 02:45:57 -0800
"H. Peter Anvin" <hpa@zytor.com> wrote:

> On 02/24/2014 10:01 PM, Chris Bainbridge wrote:
> > Pentium M is PAE capable but does not indicate so in the CPUID response.
> > This is an issue now that some distributions are no longer shipping
> > non-PAE kernels (those distributions no longer boot on Pentium M). This
> > small patch fixes the issue by forcing the PAE capability on Pentium M.
> >
> > For more discussion see https://bugs.launchpad.net/baltix/+bug/930447
> >
> 
> 1. This patch doesn't match the discussion in the link.
> 2. You would have to also enable this in the cpu testing code in
>     arch/x86/boot.
> 3. At the very least we need to print a serious warning that the CPU
>     is being run outside its specifications.  I have no personal
>     information about why this CPUID bit was disabled, but it could be
>     that it was discovered in testing that it didn't work correctly in
>     all circumstances (e.g. high temperature.)  This is very much "use
>     at your own risk..."; you could get data corruption or even
>     hardware damage.

A hang with an extended version of the no PAE message that warns you
and then says "Boot with the option "forcepae" to bypass this check",
would, IMHO, be a bit wiser, unless someone can actually dig out the
reason it does not advertise the flag.

Alan

  parent reply	other threads:[~2014-02-25 12:08 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-25  6:01 [PATCH] x86: set Pentium M as PAE capable Chris Bainbridge
2014-02-25 10:45 ` H. Peter Anvin
2014-02-25 11:35   ` Borislav Petkov
2014-02-25 12:06   ` Peter Hurley
2014-02-25 12:07   ` One Thousand Gnomes [this message]
2014-02-25 16:26   ` Dave Jones
2014-02-25 17:16     ` H. Peter Anvin
2014-02-26 12:12       ` Chris Bainbridge
2014-02-26 13:18         ` Borislav Petkov
2014-02-26 15:49           ` Dave Jones
2014-02-26 17:18             ` Borislav Petkov
2014-02-26 17:20               ` Dave Jones
2014-02-26 17:28                 ` Borislav Petkov
2014-02-28  7:30             ` Chris Bainbridge
     [not found]               ` <CAKKYfmFgVjYwvThpB0FBB+ggOwULWKLpz7ADT1eojno_KtD9yw@mail.gmail.com>
2014-02-28 14:00                 ` Chris Bainbridge
2014-03-02 20:56                   ` Andreas Mohr
2014-03-02 20:59                     ` H. Peter Anvin
2014-03-02 21:02                     ` Dave Jones
2014-03-02 21:04                       ` Borislav Petkov
2014-03-02 21:13                         ` Andreas Mohr
2014-03-02 21:42                       ` Gene Heskett
2014-03-03 12:31                         ` One Thousand Gnomes
2014-03-03  8:04                     ` Chris Bainbridge
2014-03-03 19:29                       ` Borislav Petkov
2014-03-04  5:01                         ` Chris Bainbridge
2014-03-04  5:04                           ` H. Peter Anvin
2014-03-04  6:06                             ` Chris Bainbridge
2014-03-04 10:44                               ` Borislav Petkov
2014-03-05  4:17                                 ` Chris Bainbridge
2014-03-07 11:40                                 ` [PATCH] x86: Add forcepae parameter for booting PAE kernels on PAE-disabled Pentium M Chris Bainbridge
2014-03-10 10:25                                   ` Borislav Petkov
2014-03-20 23:30                                   ` [tip:x86/cpu] x86, cpu: " tip-bot for Chris Bainbridge
2014-03-20 23:33                                   ` tip-bot for Chris Bainbridge
2014-03-20 23:30             ` [tip:x86/cpu] Rename TAINT_UNSAFE_SMP to TAINT_CPU_OUT_OF_SPEC tip-bot for Dave Jones
2014-02-26 16:46           ` [PATCH] x86: set Pentium M as PAE capable H. Peter Anvin
2014-02-26 16:44         ` Matthew Garrett
2014-02-26 16:45           ` H. Peter Anvin
2014-02-26 17:10             ` Matthew Garrett
2014-02-26 17:57               ` H. Peter Anvin
2014-03-03  0:11                 ` H. Peter Anvin
2014-03-02 19:05 Roland Kletzing

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