RE: Fw: [PATCH] ia64: race flushing icache in do_no_page path

[Rohit Seth <rohitseth@google.com>]

-----Original Message-----
From: Hugh Dickins [mailto:hugh@veritas.com] 
Sent: Friday, April 27, 2007 10:20 PM
To: Nick Piggin
Cc: rohitseth@google.com; Mike Stroyan; Andrew Morton; Luck, Tony;
linux-ia64@vger.kernel.org; linux-kernel@vger.kernel.org
Subject: Re: Fw: [PATCH] ia64: race flushing icache in do_no_page path

On Sat, 28 Apr 2007, Nick Piggin wrote:
> 
> OIC, you need a virtual address to evict the icache, so you can't 
> flush at flush_dcache time? Or does ia64 have an instruction to flush 
> the whole icache? (it would be worth testing, to see how much 
> performance suffers).

IIRC, there is a PAL call to flush the whole cache (but that is quite a
heavy call).  Though you really don't need to be doing this.

>I'm puzzled by that remark: the ia64 flush_icache_range always has a 
>virtual address, it uses the kernel virtual address; it takes 
>no interest in whether there's a user virtual address.

Caches on Itanium are physical.  So, it doesn't matter what virtual address
you use to flush a cache line, cache line containing specific physical
memory will be flushed.  For the cases where you have virtual caches,
update_mmu_cache is the API to use.

-rohit

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