linux-mips
[Top] [All Lists]

Re: [PATCH 0/2] FLATMEM: allow memory to start at pfn != 0 [take #2]

To: Franck Bui-Huu <vagabon.xyz@gmail.com>
Subject: Re: [PATCH 0/2] FLATMEM: allow memory to start at pfn != 0 [take #2]
From: peter fuerst <post@pfrst.de>
Date: Mon, 12 Mar 2007 21:02:25 +0100 (CET)
Cc: linux-mips@linux-mips.org
In-reply-to: <cda58cb80703121005h53969eb2j7b2290b97b14374d@mail.gmail.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <116841864595-git-send-email-fbuihuu@gmail.com> <Pine.LNX.4.58.0703101034500.19007@Indigo2.Peter> <cda58cb80703120247q435b6bb1p8a025d8597aca2a2@mail.gmail.com> <Pine.LNX.4.58.0703121329450.440@Indigo2.Peter> <cda58cb80703121005h53969eb2j7b2290b97b14374d@mail.gmail.com>
Reply-to: post@pfrst.de
Sender: linux-mips-bounce@linux-mips.org

Hi!

On Mon, 12 Mar 2007, Franck Bui-Huu wrote:

> Date: Mon, 12 Mar 2007 18:05:10 +0100
> From: Franck Bui-Huu <vagabon.xyz@gmail.com>
> To: post@pfrst.de
> Cc: linux-mips@linux-mips.org
> Subject: Re: [PATCH 0/2] FLATMEM: allow memory to start at pfn != 0 [take
>     #2]
>
> On 3/12/07, peter fuerst <post@pfrst.de> wrote:
> >
> > You see the problem. Any occurrence of PAGE_OFFSET must be checked.
> >
>
> yes and whatever the scheme you propose...
>
> > the kernel-addresses.  Moreover it would be desirable, if this macro
> > really could be used throughout the kernel, e.g. by drivers, handling
> > any reasonable kernel-address, which isn't possible in the page_offset
> > scheme anyway.
> >
>
> Can you explain why the current use of pa() failed to handle all
> kernel address with a real example ?

Simply, when you convert between cached (kseg0, ckseg0, several xkphys-
regions) and uncached (kseg1, ckseg1, several xkphys-regions) addresses
and the other way round, you need the physical address as an intermediate
value and __pa() or virt_to_phys() can support only one direction.

Of course a scheme, that supports all unmapped spaces (kseg0/1, ckseg0/1,
xkphys) simultaneously, or even xkphys alone, can't support TLB-mapped
spaces (kseg3, ckseg3, ..., xkseg) - at which your patch seems to aim -
and vice versa.

>
> A few people reported that they had problem with KPHYS/CKSEG0 address
> mix for 64 bit kernels but as far I can see it was due to a miss
> configuration of their kernels. Of course I canbe wrong but these

Hmm, i don't remember actually mis-configured kernels, but allright,
have to skim the eMail-archive again.

> people haven't given any feedbacks so far...
>
> Thanks
> --
>                Franck

kind regards

peter



<Prev in Thread] Current Thread [Next in Thread>