linux-kernel - RE: Fw: [PATCH] ia64: race flushing icache in do_no

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Message-Id: <200704281805.l3SI5JQx030827@smtp.corp.google.com>
Date:	Sat, 28 Apr 2007 11:05:09 -0700
From:	Rohit Seth <rohitseth@...gle.com>
To:	"'Hugh Dickins'" <hugh@...itas.com>,
	"'Nick Piggin'" <nickpiggin@...oo.com.au>
Cc:	"'Mike Stroyan'" <mike.stroyan@...com>,
	"'Andrew Morton'" <akpm@...ux-foundation.org>,
	"'Luck, Tony'" <tony.luck@...el.com>, <linux-ia64@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: RE: Fw: [PATCH] ia64: race flushing icache in do_no_page path

 

-----Original Message-----
From: Hugh Dickins [mailto:hugh@...itas.com] 
Sent: Friday, April 27, 2007 10:20 PM
To: Nick Piggin
Cc: rohitseth@...gle.com; Mike Stroyan; Andrew Morton; Luck, Tony;
linux-ia64@...r.kernel.org; linux-kernel@...r.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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