linux-kernel - Re: [PATCH 02/20] mm: Add optional TLB flush to generic RCU page-table freeing

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Date:	Thu, 28 Jun 2012 22:00:01 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-mm@...ck.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, akpm@...ux-foundation.org,
	Rik van Riel <riel@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Mel Gorman <mel@....ul.ie>, Nick Piggin <npiggin@...nel.dk>,
	Alex Shi <alex.shi@...el.com>,
	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>,
	Konrad Rzeszutek Wilk <konrad@...nok.org>,
	David Miller <davem@...emloft.net>,
	Russell King <rmk@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Chris Metcalf <cmetcalf@...era.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Tony Luck <tony.luck@...el.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Jeff Dike <jdike@...toit.com>,
	Richard Weinberger <richard@....at>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Kyle McMartin <kyle@...artin.ca>,
	James Bottomley <jejb@...isc-linux.org>,
	Chris Zankel <chris@...kel.net>
Subject: Re: [PATCH 02/20] mm: Add optional TLB flush to generic RCU
 page-table freeing

On Thu, 2012-06-28 at 13:05 +0200, Peter Zijlstra wrote:
> 
> > Some embedded ppc's know about the lowest level (SW loaded PMD) but
> > that's not an issue here. We flush these special TLB entries
> > specifically and synchronously in __pte_free_tlb().
> 
> OK, I missed that.. is that
> arch/powerpc/mm/tlb_nohash.c:tlb_flush_pgtable() ?

Yup.

> > > So even if the hardware did do speculative tlb fills, it would do
> them
> > > from the hash-table, but that's already cleared out.
> > 
> > Right,
> 
> Phew at least I got the important thing right ;-)

Yeah as long as we have that hash :-) The day we move on (if ever) it
will be as bad as ARM :-)

Cheers,
Ben.


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