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Re: Kernel crash in 2.6.32.6 / bcm1480 with 16k page size

To: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: Kernel crash in 2.6.32.6 / bcm1480 with 16k page size
From: Guenter Roeck <guenter.roeck@ericsson.com>
Date: Mon, 1 Feb 2010 13:12:17 -0800
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>, David Daney <ddaney@caviumnetworks.com>, "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>
In-reply-to: <20100201204912.GC17381@linux-mips.org>
Organization: Ericsson
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20100129180619.GA20113@linux-mips.org> <20100129183926.GB9895@ericsson.com> <4B632F60.4000604@caviumnetworks.com> <20100129192532.GA11123@ericsson.com> <4B6336F1.8070208@caviumnetworks.com> <20100129195801.GC11123@ericsson.com> <alpine.LFD.2.00.1001310907320.31764@eddie.linux-mips.org> <20100131165503.GA18523@ericsson.com> <20100201021854.GA8572@linux-mips.org> <1265055677.5825.47.camel@groeck-laptop> <20100201204912.GC17381@linux-mips.org>
Reply-to: guenter.roeck@ericsson.com
Sender: linux-mips-bounce@linux-mips.org
On Mon, 2010-02-01 at 15:49 -0500, Ralf Baechle wrote:
> On Mon, Feb 01, 2010 at 12:21:17PM -0800, Guenter Roeck wrote:
> 
> > > Write a value with all bits set to c0_entryhi, then read it back again.
> > > The set bits in the VPN2 bitfield will indicate the size of the virtual
> > > address range supported.  The MIPS64 documentation also calls this value
> > > SEGBITS.  The nice thing about this probe is that it is supported for
> > > all 64-bit MIPS processors except the R8000 which has an entirely 
> > > different
> > > TLB scheme anyway.
> > 
> > Are you sure that this doesn't work for the R8000 ? From the user's
> > manual (section 2.1.9, EntryHi) it looks like it should work.
> 
> The probe itself will work if it's carefully written not to get fooled by
> difference in bits 12..18 but that's easy) but still the R8000 has a fairly
> different TLB architecture which Linux doesn't support - the machines are
> rare and none of the active developers has one.
> 
Looks like my code should work. I'll send out a patch in a couple of
minutes.

Guenter



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