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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 12:21:17 -0800
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On Sun, 2010-01-31 at 21:18 -0500, Ralf Baechle wrote:
> On Sun, Jan 31, 2010 at 08:55:03AM -0800, Guenter Roeck wrote:
> 
> > >  The size of the address space can be probed via CP0 registers (for MIPS 
> > > architecture processors that is).  No need to add any CPU dependencies 
> > > (except from legacy 64-bit MIPS processors perhaps).
> > > 
> > That would help. Do you happen to know which CP0 register(s) to look for ? 
> > I browsed through the MIPS 5K and 20Kc manuals, but didn't find it.
> 
> 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.

Guenter