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

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Message-Id: <1236964416.4529.125.camel@localhost.localdomain>
Date:	Fri, 13 Mar 2009 10:13:36 -0700
From:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
To:	Frank Mehnert <Frank.Mehnert@....COM>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
Subject: Re: remap_pfn_range() not suitable for physical RAM?


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
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> 
> 
> 

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