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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: "Maciej W. Rozycki" <macro@linux-mips.org>
Date: Mon, 1 Feb 2010 14:50:27 +0000 (GMT)
Cc: Guenter Roeck <guenter.roeck@ericsson.com>, David Daney <ddaney@caviumnetworks.com>, "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>
In-reply-to: <20100201021854.GA8572@linux-mips.org>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20100129151220.GA3882@ericsson.com> <4B6316D2.1060006@caviumnetworks.com> <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>
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On Mon, 1 Feb 2010, Ralf Baechle 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.
> 
> Similarly it is possible to probe the physical address range in either
> c0_entrylo0 or c0_entrylo1.  This is also of interest on 32-bit processors.

 Indeed -- IIRC the architecture spec calls this value PABITS.  I wasn't 
sure about the legacy processors -- if that works with them too, then it's 
even better.

  Maciej

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