From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [203.10.76.45]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mx.ozlabs.org", Issuer "CA Cert Signing Authority" (verified OK)) by bilbo.ozlabs.org (Postfix) with ESMTPS id 1532EB6F1F for ; Tue, 21 Jul 2009 17:06:06 +1000 (EST) Received: from mx1.suse.de (cantor.suse.de [195.135.220.2]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mx1.suse.de", Issuer "CAcert Class 3 Root" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 561ABDDD0B for ; Tue, 21 Jul 2009 17:06:05 +1000 (EST) Date: Tue, 21 Jul 2009 09:05:58 +0200 From: Nick Piggin To: Benjamin Herrenschmidt Subject: Re: [RFC/PATCH] mm: Pass virtual address to [__]p{te, ud, md}_free_tlb() Message-ID: <20090721070558.GA7816@wotan.suse.de> References: <20090715074952.A36C7DDDB2@ozlabs.org> <20090715135620.GD7298@wotan.suse.de> <1247709255.27937.5.camel@pasglop> <20090720081054.GH7298@wotan.suse.de> <1248084041.30899.7.camel@pasglop> <20090720103835.GB7070@wotan.suse.de> <1248134546.30899.27.camel@pasglop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1248134546.30899.27.camel@pasglop> Cc: Linux-Arch , Linux Memory Management , Hugh Dickins , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Jul 21, 2009 at 10:02:26AM +1000, Benjamin Herrenschmidt wrote: > On Mon, 2009-07-20 at 12:38 +0200, Nick Piggin wrote: > > On Mon, Jul 20, 2009 at 08:00:41PM +1000, Benjamin Herrenschmidt wrote: > > > On Mon, 2009-07-20 at 10:10 +0200, Nick Piggin wrote: > > > > > > > > Maybe I don't understand your description correctly. The TLB contains > > > > PMDs, but you say the HW still logically performs another translation > > > > step using entries in the PMD pages? If I understand that correctly, > > > > then generic mm does not actually care and would logically fit better > > > > if those entries were "linux ptes". > > > > > > They are :-) > > > > > > > The pte invalidation routines > > > > give the virtual address, which you could use to invalidate the TLB. > > > > > > For PTEs, yes, but not for those PMD entries. IE. I need the virtual > > > address when destroying PMDs so that I can invalidate those "indirect" > > > pages. PTEs are already taken care of by existing mechanisms. > > > > Hmm, so even after having invalidated all the pte translations > > then you still need to invalidate the empty indirect page? (or > > maybe you don't even invalidate the ptes if they're not cached > > in a TLB). > > The PTEs are cached in the TLB (ie, they turn into normal TLB entries). > > We need to invalidate the indirect entries when the PMD value change > (ie, when the PTE page is freed) or the TLB would potentially continue > loading PTEs from a stale PTE page :-) > > Hence my patch adding the virtual address to pte_free_tlb() which is the > freeing of a PTE page. I'm adding it to the pmd/pud variants too for > consistency and because I believe there's no cost. Yes I think we're on the same page now. So as I said, the patch is quite OK with me.