Hi David,
Is this just sun4c or does it affect other sparc32 architectures.
Regards
Mark Fortescue.
On Mon, 30 Apr 2007, David Miller wrote:
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Date: Mon, 30 Apr 2007 14:54:14 -0700
On Mon, 30 Apr 2007 22:36:27 +0100 (BST)
Mark Fortescue <mark@xxxxxxxxxxxxxxxxxx> wrote:
Hi all,
I have tracked down a failure to successfully load/run the init task on my
Sparcstation 1 clone (SS1) and Sparcstation 2 (SS2), sparc32 sun4c
systems, to a patch:
commit 1a44e149084d772a1bcf4cdbdde8a013a8a1cfde.
[PATCH] .text page fault SMP scalability optimization
Removing this patch fixes the issue and allows me to use kernels later
than v2.5.14. (tested using linux-2.6.20.9).
Given the comment provided by the git bisect, backing out this patch will
probably have undesirable conseqnences for other platforms (especially
powerpc64) so, if an architecture independent solution is not available,
some/all of the code in handle_pte_fault() in mm/memory.c will need be to
made architecture dependent.
I am not sufficiently familear with the how the SS1/SS2 mmu works and how
the linux memory management system works to understand why this patch
prevents my sun4c SS1/SS2 systems from working.
Advice and help on the approch to take and any code changes regarding this
issue would be most welcome.
Interesting - thanks for working that out. Let's keep linux-mm on cc please.
You can't elide the update_mmu_cache() call on sun4c because that will
miss some critical TLB setups which are performed there.
The sun4c TLB has two tiers of entries:
1) segment maps, these hold ptes for a range of addresses
2) ptes, mapped into segment maps
update_mmu_cache() on sun4c take care of allocating and setting
up the segment maps, so if you elide the call this never happens
and we fault forever.
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