linux-kernel - Re: [RFC/PATCH] mm: Pass virtual address to [__]p{te,ud,md}_free

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Date:	Mon, 20 Jul 2009 13:46:03 +0100
From:	David Howells <dhowells@...hat.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	dhowells@...hat.com, Linux Memory Management <linux-mm@...ck.org>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	Hugh Dickins <hugh@...cali.co.uk>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: [RFC/PATCH] mm: Pass virtual address to [__]p{te,ud,md}_free_tlb()

Benjamin Herrenschmidt <benh@...nel.crashing.org> wrote:

> Upcoming paches to support the new 64-bit "BookE" powerpc architecture
> will need to have the virtual address corresponding to PTE page when
> freeing it, due to the way the HW table walker works.
> 
> Basically, the TLB can be loaded with "large" pages that cover the whole
> virtual space (well, sort-of, half of it actually) represented by a PTE
> page, and which contain an "indirect" bit indicating that this TLB entry
> RPN points to an array of PTEs from which the TLB can then create direct
> entries. Thus, in order to invalidate those when PTE pages are deleted,
> we need the virtual address to pass to tlbilx or tlbivax instructions.
>
> The old trick of sticking it somewhere in the PTE page struct page sucks
> too much, the address is almost readily available in all call sites and
> almost everybody implemets these as macros, so we may as well add the
> argument everywhere. I added it to the pmd and pud variants for consistency.
> 
> Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>

Acked-by: David Howells <dhowells@...hat.com> [MN10300 & FRV]
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