linux-kernel - Re: remap_pfn_range() not suitable for physical RAM?

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Message-id: <200903141244.45321.frank.mehnert@sun.com>
Date:	Sat, 14 Mar 2009 12:44:42 +0100
From:	Frank Mehnert <Frank.Mehnert@....COM>
To:	linux-kernel@...r.kernel.org
Cc:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
Subject: Re: remap_pfn_range() not suitable for physical RAM?

Venki,

thanks for these explanations. So vm_insert_page() is only meant for
RAM pages and remap_pfn_range() can be used for any mappings (inclusive
I/O memory), is that right?

Thanks,

Frank

On Friday 13 March 2009, Pallipadi, Venkatesh wrote:
> Frank,
>
> The track and untrack is keeping track of memory type for non-RAM
> regions and making sure that the type is in sync for various mappings
> for such addresses. We are not tracking the RAM pages today, so
> vm_insert_page does not have this. vm_insert_mixed is also not covered
> today, as we deferred that and tracking of RAM pages into our next set
> of changes.
>
> Thanks,
> Venki
>
> On Fri, 2009-03-13 at 08:00 -0700, Frank Mehnert wrote:
> > Venki,
> >
> > thanks for your reply. May I ask anyway why this check is done in
> > remap_pfn_range() and vm_insert_pfn() but not in vm_insert_page()?
> >
> > Kind regards,
> >
> > Frank
> >
> > On Tuesday 10 March 2009, Pallipadi, Venkatesh wrote:
> > > Frank,
> > >
> > > Patch here should eliminate the restriction.
> > > http://marc.info/?l=linux-kernel&m=123664923030126&w=1
> > >
> > > Thanks,
> > > Venki
> > >
> > > >-----Original Message-----
> > > >From: linux-kernel-owner@...r.kernel.org
> > > >[mailto:linux-kernel-owner@...r.kernel.org] On Behalf Of Frank Mehnert
> > > >Sent: Tuesday, March 10, 2009 1:04 AM
> > > >To: linux-kernel@...r.kernel.org
> > > >Cc: peterz@...radead.org; Siddha, Suresh B
> > > >Subject: Re: remap_pfn_range() not suitable for physical RAM?
> > > >
> > > >Hi,
> > > >
> > > >sorry for re-posting this message and sorry for addressing you
> > > >directly.
> > > >Perhaps you can help me again or can you give me a pointer for a
> > > > proper documentation of the various *remap* and *vm_insert*
> > > > functions:
> > > >
> > > >On Wednesday 04 March 2009, Frank Mehnert wrote:
> > > >> since 2.6.29-rcX it seems to be not allowed anymore to use
> > > >> remap_pfn_range() to remap physical RAM to userland. This
> > > >> restriction applies only if CONFIG_X86_PAT is enabled. It seems that
> > > >
> > > >vm_insert_page()
> > > >
> > > >> does not have this restriction. Am I correct? And what is the reason
> > > >> for this restriction?
> > > >
> > > >Kind regards,
> > > >
> > > >Frank
> > > >--
> > > >Dr.-Ing. Frank Mehnert    Sun Microsystems    http://www.sun.com/
> > > >--
> > >
> > > To unsubscribe from this list: send the line "unsubscribe linux-kernel"
> > > in the body of a message to majordomo@...r.kernel.org
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> > > Please read the FAQ at  http://www.tux.org/lkml/
>
> --
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-- 
Dr.-Ing. Frank Mehnert    Sun Microsystems    http://www.sun.com/

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