* Linux: PG_pinned vs. PG_foreign
@ 2007-01-15 9:38 Jan Beulich
2007-01-15 10:10 ` Keir Fraser
0 siblings, 1 reply; 3+ messages in thread
From: Jan Beulich @ 2007-01-15 9:38 UTC (permalink / raw)
To: xen-devel
Is it intentional that these two both use PG_arch_1? It seems at least risky
to me... And if intended, it would certainly deserve a comment. (I was about
to utilize PG_pinned for indicating pinned highmem-allocated PTEs when I
realized this collision.)
Thanks, Jan
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Linux: PG_pinned vs. PG_foreign
2007-01-15 9:38 Linux: PG_pinned vs. PG_foreign Jan Beulich
@ 2007-01-15 10:10 ` Keir Fraser
2007-01-15 11:36 ` Jan Beulich
0 siblings, 1 reply; 3+ messages in thread
From: Keir Fraser @ 2007-01-15 10:10 UTC (permalink / raw)
To: Jan Beulich, xen-devel
On 15/1/07 09:38, "Jan Beulich" <jbeulich@novell.com> wrote:
> Is it intentional that these two both use PG_arch_1? It seems at least risky
> to me... And if intended, it would certainly deserve a comment. (I was about
> to utilize PG_pinned for indicating pinned highmem-allocated PTEs when I
> realized this collision.)
There's no reason to have them use the same bit if there's a PG_arch_2
available. It was probbaly laziness on my part when I realised that (so far)
ForeignPage and Pinned are mutually exclusive.
-- Keir
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Linux: PG_pinned vs. PG_foreign
2007-01-15 10:10 ` Keir Fraser
@ 2007-01-15 11:36 ` Jan Beulich
0 siblings, 0 replies; 3+ messages in thread
From: Jan Beulich @ 2007-01-15 11:36 UTC (permalink / raw)
To: xen-devel, Keir Fraser
>>> Keir Fraser <keir@xensource.com> 15.01.07 11:10 >>>
>On 15/1/07 09:38, "Jan Beulich" <jbeulich@novell.com> wrote:
>
>> Is it intentional that these two both use PG_arch_1? It seems at least risky
>> to me... And if intended, it would certainly deserve a comment. (I was about
>> to utilize PG_pinned for indicating pinned highmem-allocated PTEs when I
>> realized this collision.)
>
>There's no reason to have them use the same bit if there's a PG_arch_2
>available. It was probbaly laziness on my part when I realised that (so far)
>ForeignPage and Pinned are mutually exclusive.
There isn't, but there are a few bits left, so that shouldn't be a problem.
PG_foreign really should be a standalone one, not using PR_arch_1, as
arches may have or get a meaning assigned for this (ia64 specifically has),
so even if it isn't a problem today it is very much like a latent bug.
I'll try to send a respective patch soon, but since I want to use this in our
code, too, I first have to resolve a collision with s390 patches from IBM,
which consume all the remaining bit positions.
Jan
^ permalink raw reply [flat|nested] 3+ messages in thread
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2007-01-15 9:38 Linux: PG_pinned vs. PG_foreign Jan Beulich
2007-01-15 10:10 ` Keir Fraser
2007-01-15 11:36 ` Jan Beulich
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