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2.6.28 will not boot on 24K processor, ebase incorrectly modified in set

To: <linux-mips@linux-mips.org>
Subject: 2.6.28 will not boot on 24K processor, ebase incorrectly modified in set_uncached_handler
From: "David VomLehn (dvomlehn)" <dvomlehn@cisco.com>
Date: Sat, 24 Jan 2009 20:59:42 -0500
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Cc: "Dezhong Diao (dediao)" <dediao@cisco.com>, "Victor Williams Jr (williavi)" <williavi@cisco.com>, "Michael Sundius -X (msundius - Yoh Services LLC at Cisco)" <msundius@cisco.com>
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Thread-topic: 2.6.28 will not boot on 24K processor, ebase incorrectly modified in set_uncached_handler
The 2.6.28 kernel dies in memcpy when called from set_vi_srs_handler on
a
24K processor. The problem is that ebase has an invalid value. The
original
value of ebase comes from a bootmem allocation, but the following code
in
set_uncached_handler takes a perfectly good kseg0 address and turns it
into
an invalid kseg1 address.

        if (cpu_has_mips_r2)
                ebase += (read_c0_ebase() & 0x3ffff000);

This code was added in commit 566f74f6b2f8b85d5b8d6caaf97e5672cecd3e3e.
I
have no idea why ebase needs to be modified at all, so I have no patch
to
offer. When I removed these two lines, my kernel booted to a shell
prompt.
--
David VomLehn, dvomlehn@cisco.com


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