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icache flushing (Re: Broadcom Swarm support)

Subject: icache flushing (Re: Broadcom Swarm support)
From: Atsushi Nemoto <>
Date: Thu, 25 Jun 2009 10:48:24 +0900 (JST)
In-reply-to: <DDFD17CC94A9BD49A82147DDF7D545C501C3539B@exchange.ZeugmaSystems.local>
Original-recipient: rfc822;
References: <> <DDFD17CC94A9BD49A82147DDF7D545C501C3539B@exchange.ZeugmaSystems.local>
On Wed, 24 Jun 2009 15:18:24 -0700, "Kaz Kylheku" <> 
> At some point in the kernel history, Ralfie decided that
> the flush_icache_page function is unnecessary and
> turned it into a MIPS-wide noop. But the SB1 core, which has
> a VIVT instruction cache, it appears that there
> is some kind of issue whereby when it
> is handling a fault for a not-present virtual page,
> it somehow ends up with bad data in the instruction
> cache---perhaps an inconsistent state due to not having
> been able to complete the fetch, but having initiated
> a cache update on the expectation that the fetch
> will complete. It seems that the the fault handler
> is expected to do a flush.

Looking at current code, I also have some questions aboud icache

* flush_cache_mm does not flush icache.  Is it OK?

* flush_cache_{vmap,vunmap} does not flush icache.  When icache used
  by modules flushed after unloading?

* __update_cache, copy_user_highpage does not flush icache even if
  !cpu_has_ic_fills_f_dc.  Is it OK?

* free_initmem does not flush icache.  When these init pages are
  reused, how corresponding icache will be flushed?

I suppose flushing icache in flush_icache_page() will hide real bugs
somewhere else...

Atsushi Nemoto

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