On Sat, Jul 27, 2013 at 05:10:56AM +0100, Paul Walmsley wrote:
>
> Tonight I put on a Jon Hopkins album, in recollection of my UK ARM Linux
> colleagues perhaps, and started testing, and eventually wound up with this
> one:
>
> commit 621a0147d5c921f4cc33636ccd0602ad5d7cbfbc
> Author: Will Deacon <will.deacon@xxxxxxx>
Oh, great...
> Date: Wed Jun 12 12:25:56 2013 +0100
>
> ARM: 7757/1: mm: don't flush icache in switch_mm with hardware broadcasting
>
> When scheduling an mm on a CPU where it hasn't previously been used, we
> flush the icache on that CPU so that any code loaded previously on
> a different core can be safely executed.
>
> For cores with hardware broadcasting of cache maintenance operations,
> this is clearly unnecessary, since the inner-shareable invalidation in
> __sync_icache_dcache will affect all CPUs.
>
> This patch conditionalises the icache flush in switch_mm based on
> cache_ops_need_broadcast().
>
> Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Reported-by: Albin Tonnerre <albin.tonnerre@xxxxxxx>
> Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
> Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
>
> ...
>
> v3.11-rc2 boots with it reverted. What also works is v3.11-rc2 with the
> below patch applied.
That's very odd -- I *suspect* your bootloader is up to no good (iirc, we've
had issues with the bootloader on this machine in the past, since it enters
the kernel in ABT mode or something).
> Would be pleased to boot-test anything you'd care to send my way, as long
> as you can tolerate response latency jitter.
Can you try this quick hack please? It clobbers the I-cache as soon as we
enter the kernel, so it should tell us whether my theory is correct.
Cheers,
Will
--->8
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 9cf6063..d74c64c 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -83,6 +83,9 @@ ENTRY(stext)
THUMB( .thumb ) @ switch to Thumb now.
THUMB(1: )
+ mov r9, #0
+ mcr p15, 0, r9, c7, c5, 0
+
#ifdef CONFIG_ARM_VIRT_EXT
bl __hyp_stub_install
#endif
--
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