lkml.org 
[lkml]   [2011]   [Jun]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/3] x86: calculate precisely the memory needed by init_memory_mapping
On Mon, 20 Jun 2011, H. Peter Anvin wrote:
> On 06/07/2011 11:13 AM, stefano.stabellini@eu.citrix.com wrote:
> >
> > - remove the extra page added on x86_32 for the fixmap because is not
> > needed: the PMD entry is already allocated and contiguous for the whole
> > range (a PMD page covers 4G of virtual addresses) and the pte entry is
> > already allocated by early_ioremap_init.
> >
>
> Hi Stefano,
>
> I think this is wrong. A PMD page covers *1G* of virtual addresses, and
> in the 2+2 and 1+3 memory configurations, we may or may not need a
> separate PMD for the fixmap.
>
> Am I missing something?

You are right, a PMD page covers 1G of virtual addresses so that part of
the explanation in the comment is wrong.

The reason why we don't need a separate PMD for the fixmap is that in
both PAE and non-PAE cases the last gigabyte of virtual addresses is
always covered by the initial allocation in head_32.S (swapper_pg_dir or
initial_pg_pmd).


\
 
 \ /
  Last update: 2011-06-21 19:55    [W:0.056 / U:0.228 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site