On Thu, Oct 10, 2013 at 10:44:54AM +0000, Bhushan Bharat-R65777 wrote: > > > > -----Original Message----- > > From: Paul Mackerras [mailto:paulus@xxxxxxxxx] > > Sent: Thursday, October 10, 2013 4:06 PM > > To: Wood Scott-B07421 > > Cc: Bhushan Bharat-R65777; Wood Scott-B07421; agraf@xxxxxxx; Yoder Stuart- > > B08248; kvm@xxxxxxxxxxxxxxx; kvm-ppc@xxxxxxxxxxxxxxx > > Subject: Re: [PATCH 3/4] kvm: powerpc: define a linux pte lookup function > > > > 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. > > Do we want to have lookup_linux_pte() or lookup_linux_ptep() or both where lookup_linux_pte() and lookup_linux_pte_and_update() calls lookup_linux_ptep() ? I don't think we want both lookup_linux_pte() and lookup_linux_ptep(). Either have a lookup_linux_ptep() and call it from your book E code and from lookup_linux_pte_and_update(), or keep a separate lookup_linux_pte() and don't make the _and_update() version call it. I don't really care; you decide which looks nicer in the end. Of course someone will then tell you to do it the other way, but at that point it's just a matter of taste. Paul. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
