From: Andi Kleen <andi@firstfloor.org>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Jan Beulich <jbeulich@novell.com>,
Stable Kernel <stable@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH UPDATED] x86: set PAE PHYSICAL_MASK_SHIFT to 44 bits.
Date: Fri, 06 Jun 2008 15:15:37 +0200 [thread overview]
Message-ID: <87lk1iu2km.fsf@basil.nowhere.org> (raw)
In-Reply-To: <484901A3.3040401@goop.org> (Jeremy Fitzhardinge's message of "Fri, 06 Jun 2008 10:21:39 +0100")
Jeremy Fitzhardinge <jeremy@goop.org> writes:
> When a 64-bit x86 processor runs in 32-bit PAE mode, a pte can
> potentially have the same number of physical address bits as the
> 64-bit host ("Enhanced Legacy PAE Paging"). This means, in theory,
> we could have up to 52 bits of physical address in a pte.
>
> The 32-bit kernel uses a 32-bit unsigned long to represent a pfn.
> This means that it can only represent physical addresses up to 32+12=44
> bits wide. Rather than widening pfns everywhere, just set 2^44 as the
> Linux x86_32-PAE architectural limit for physical address size.
43bits might be actally safer because of potential sign bugs.
But of course it won't work anyways likely.
-Andi
next prev parent reply other threads:[~2008-06-06 13:16 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-05 15:21 [PATCH] x86: set PAE PHYSICAL_MASK_SHIFT to match 64-bit Jeremy Fitzhardinge
2008-06-05 15:34 ` Jan Beulich
2008-06-05 15:42 ` Jeremy Fitzhardinge
2008-06-05 16:45 ` H. Peter Anvin
2008-06-05 21:14 ` Jeremy Fitzhardinge
2008-06-07 18:35 ` H. Peter Anvin
2008-06-06 9:21 ` [PATCH UPDATED] x86: set PAE PHYSICAL_MASK_SHIFT to 44 bits Jeremy Fitzhardinge
2008-06-06 9:58 ` Jan Beulich
2008-06-06 13:15 ` Andi Kleen [this message]
2008-06-06 13:50 ` Jeremy Fitzhardinge
2008-06-10 10:31 ` Ingo Molnar
2008-06-10 13:06 ` Jeremy Fitzhardinge
2008-06-13 7:24 ` Ingo Molnar
2008-06-06 1:40 ` [PATCH] x86: set PAE PHYSICAL_MASK_SHIFT to match 64-bit Andi Kleen
2008-06-06 7:14 ` Jan Beulich
2008-06-06 7:59 ` Jeremy Fitzhardinge
2008-06-06 8:14 ` Jan Beulich
2008-06-06 8:15 ` Jeremy Fitzhardinge
2008-06-07 18:39 ` H. Peter Anvin
2008-06-06 4:45 ` Arjan van de Ven
2008-06-06 8:08 ` Jeremy Fitzhardinge
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