From: Stefan Richter <stefanr@s5r6.in-berlin.de>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-arch@vger.kernel.org,
linux1394-devel@lists.sourceforge.net,
Clemens Ladisch <clemens@ladisch.de>
Subject: Re: PAGE_KERNEL_RO
Date: Thu, 13 Jan 2011 07:34:58 +0100 [thread overview]
Message-ID: <20110113073458.2179590a@stein> (raw)
In-Reply-To: <1294877484.9586.66.camel@pasglop>
On Jan 13 Benjamin Herrenschmidt wrote at linux-arch:
> On Wed, 2011-01-12 at 16:07 -0800, Andrew Morton wrote:
> > drivers/firewire/ohci.c now needs PAGE_KERNEL_RO, but many
> > architectures don't implement it. Broke my sparc64 build.
>
> Some architectures actually cannot implement it even... at least some
> variants of powerpc MMUs don't have a combination of protection bits
> that allow a kernel-only RO mapping (yeah odd).
The simplest perceivable fix, to disable firewire-ohci on architectures
which don't have PAGE_KERNEL_RO, would be bad since there are actually
sparc64 machines with these controllers.
As far as I can tell, the new RO mapping in firewire-ohci can as well be
an r/w mapping. We just never need to write at these virtual addresses.
So, should we just change the driver to map it r/w when we can't have
PAGE_KERNEL_RO, or for simplicity on all architectures?
--
Stefan Richter
-=====-==-== ---= -==-=
http://arcgraph.de/sr/
next prev parent reply other threads:[~2011-01-13 6:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-13 0:07 PAGE_KERNEL_RO Andrew Morton
2011-01-13 0:11 ` PAGE_KERNEL_RO Benjamin Herrenschmidt
2011-01-13 6:34 ` Stefan Richter [this message]
[not found] ` <522C1DF17AF50042AD8AE87F7887BD3D01E1655529@exch.hq.tensilica.com>
2011-01-13 7:27 ` PAGE_KERNEL_RO Clemens Ladisch
2011-01-13 9:04 ` PAGE_KERNEL_RO James Bottomley
2011-01-13 9:12 ` PAGE_KERNEL_RO Clemens Ladisch
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