From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Mackerras Date: Thu, 10 Oct 2013 10:35:40 +0000 Subject: Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function Message-Id: <20131010103540.GD9906@iris.ozlabs.ibm.com> List-Id: References: <1381212212-29641-1-git-send-email-Bharat.Bhushan@freescale.com> <1381212212-29641-4-git-send-email-Bharat.Bhushan@freescale.com> <1381268203.7979.276.camel@snotra.buserror.net> <6A3DF150A5B70D4F9B66A25E3F7C888D071A8AD0@039-SN2MPN1-012.039d.mgd.msft.net> <1381340851.7979.327.camel@snotra.buserror.net> In-Reply-To: <1381340851.7979.327.camel@snotra.buserror.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Scott Wood Cc: Bhushan Bharat-R65777 , Wood Scott-B07421 , "agraf@suse.de" , Yoder Stuart-B08248 , "kvm@vger.kernel.org" , "kvm-ppc@vger.kernel.org" On Wed, Oct 09, 2013 at 12:47:31PM -0500, Scott Wood wrote: > On Wed, 2013-10-09 at 03:48 -0500, Bhushan Bharat-R65777 wrote: > > > > What lookup_linux_pte_and_update() does:- > > - find_linux_pte_or_hugepte() > > - does size and some other trivial checks > > - Then atomically update the pte:- > > => while() > > => wait till _PAGE_BUSY is clear > > => atomically update the pte > > => if not updated then go back to while() above else break > > > > > > While what lookup_linux_pte() does:- > > - find_linux_pte_or_hugepte() > > - does size and some other trivial checks > > - wait till _PAGE_BUSY is clear > > - return pte > > > > I am finding it difficult to call lookup_linux_pte() from lookup_linux_pte_and_update(). > > You could factor out a common lookup_linux_ptep(). I don't really think it's enough code to be worth wringing out the last drop of duplication. However, if he removed the checks for _PAGE_BUSY and _PAGE_PRESENT as I suggested in another mail, and made it return the pte pointer rather than the value, it would then essentially be a lookup_linux_ptep() as you suggest. Paul. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Mackerras Subject: Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function Date: Thu, 10 Oct 2013 21:35:40 +1100 Message-ID: <20131010103540.GD9906@iris.ozlabs.ibm.com> References: <1381212212-29641-1-git-send-email-Bharat.Bhushan@freescale.com> <1381212212-29641-4-git-send-email-Bharat.Bhushan@freescale.com> <1381268203.7979.276.camel@snotra.buserror.net> <6A3DF150A5B70D4F9B66A25E3F7C888D071A8AD0@039-SN2MPN1-012.039d.mgd.msft.net> <1381340851.7979.327.camel@snotra.buserror.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Bhushan Bharat-R65777 , Wood Scott-B07421 , "agraf@suse.de" , Yoder Stuart-B08248 , "kvm@vger.kernel.org" , "kvm-ppc@vger.kernel.org" To: Scott Wood Return-path: Received: from ozlabs.org ([203.10.76.45]:48800 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752019Ab3JJKfo (ORCPT ); Thu, 10 Oct 2013 06:35:44 -0400 Content-Disposition: inline In-Reply-To: <1381340851.7979.327.camel@snotra.buserror.net> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Oct 09, 2013 at 12:47:31PM -0500, Scott Wood wrote: > On Wed, 2013-10-09 at 03:48 -0500, Bhushan Bharat-R65777 wrote: > > > > What lookup_linux_pte_and_update() does:- > > - find_linux_pte_or_hugepte() > > - does size and some other trivial checks > > - Then atomically update the pte:- > > => while() > > => wait till _PAGE_BUSY is clear > > => atomically update the pte > > => if not updated then go back to while() above else break > > > > > > While what lookup_linux_pte() does:- > > - find_linux_pte_or_hugepte() > > - does size and some other trivial checks > > - wait till _PAGE_BUSY is clear > > - return pte > > > > I am finding it difficult to call lookup_linux_pte() from lookup_linux_pte_and_update(). > > You could factor out a common lookup_linux_ptep(). I don't really think it's enough code to be worth wringing out the last drop of duplication. However, if he removed the checks for _PAGE_BUSY and _PAGE_PRESENT as I suggested in another mail, and made it return the pte pointer rather than the value, it would then essentially be a lookup_linux_ptep() as you suggest. Paul.