From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from caramon.arm.linux.org.uk ([217.147.92.249]:47882 "EHLO caramon.arm.linux.org.uk") by vger.kernel.org with ESMTP id S1162877AbWLBJt5 (ORCPT ); Sat, 2 Dec 2006 04:49:57 -0500 Date: Sat, 2 Dec 2006 09:49:29 +0000 From: Russell King Subject: Re: [PATCH 1/3] Fix COW D-cache aliasing on fork Message-ID: <20061202094929.GA12294@flint.arm.linux.org.uk> References: <20061020214916.GA27810@linux-mips.org> <20061020.152247.111203913.davem@davemloft.net> <20061020225118.GA30965@linux-mips.org> <20061021000609.GA32701@linux-mips.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org To: Linus Torvalds Cc: Ralf Baechle , David Miller , nickpiggin@yahoo.com.au, akpm@osdl.org, linux-kernel@vger.kernel.org, anemo@mba.ocn.ne.jp, linux-arch@vger.kernel.org, schwidefsky@de.ibm.com, James.Bottomley@steeleye.com List-ID: On Fri, Oct 20, 2006 at 05:38:32PM -0700, Linus Torvalds wrote: > On Sat, 21 Oct 2006, Ralf Baechle wrote: > > > That said, maybe nobody does that. Virtual caches are a total braindamage > > > in the first place, so hopefully they have limited use. > > > > On MIPS we never had pure virtual caches. > > Ok, so on MIPS my schenario doesn't matter. > > I think (but may be mistaken) that ARM _does_ have pure virtual caches > with a process ID, but people have always ended up flushing them at > context switch simply because it just causes too much trouble. Just read this, sorry. The majority of ARM CPU implementations have pure virtual caches _without_ process IDs. (Some have a nasty hack which involves remapping the lower 32MB of virtual memory space to other areas of the cache's virtual space, but obviously that limits you to 32MB of VM.) Thankfully, with ARM version 6, they had an inkling of clue, and decided to move to VIPT caches but with _optional_ aliasing, and if the CPU design was Harvard there's a possibility for D/I cache aliasing. > > Be sure I'm sending a CPU designers a strong message about aliases. > > Castration. That's the best solution. We don't want those people > procreating. Absolutely. Can we start such a program in Cambridge, England ASAP please? -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: