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Subject: Re: Kernel crash in 2.6.32.6 / bcm1480 with 16k page size
From:   Guenter Roeck <guenter.roeck@ericsson.com>
Reply-To: guenter.roeck@ericsson.com
To:     Ralf Baechle <ralf@linux-mips.org>
CC:     "Maciej W. Rozycki" <macro@linux-mips.org>,
        David Daney <ddaney@caviumnetworks.com>,
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Organization: Ericsson
Date:   Mon, 1 Feb 2010 13:12:17 -0800
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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