From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: Re: [patch 05/21] Xen-paravirt: paravirt_ops: allocate a fixmap slot Date: 14 Feb 2007 10:15:04 +0100 Message-ID: <20070214091504.GA68112@muc.de> References: <20070213221729.772002682@goop.org> <20070213221829.845132535@goop.org> <45D2649D.4080508@vmware.com> <45D26797.5090600@goop.org> <45D2D856.76E4.0078.0@novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Date: Wed, 14 Feb 2007 10:15:04 +0100 Content-Disposition: inline In-Reply-To: <45D2D856.76E4.0078.0@novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jan Beulich Cc: Andrew Morton , Jeremy Fitzhardinge , xen-devel@lists.xensource.com, Dan Hecht , linux-kernel@vger.kernel.org, Chris Wright , virtualization@lists.osdl.org List-Id: virtualization@lists.linuxfoundation.org On Wed, Feb 14, 2007 at 08:37:26AM +0000, Jan Beulich wrote: > >>> Jeremy Fitzhardinge 14.02.07 02:36 >>> > >Dan Hecht wrote: > >> Why doesn't Xen allocate the shared_info page from the pseudo-physical > >> space? Doesn't it already have to steal pages from the > >> pseudo-physical space for e.g. initial page tables, console, etc? Why > >> not do the same for shared_info, and then you don't need a reserve the > >> fixmap slot. > > > >Unlike the pagetable pages or the console page, the shared info page > >doesn't have a pseudo-physical address, so in order to map it we need to > >directly construct a pte containing the mfn for that page. Inserting > >this mapping into the fixmap space seems like the easiest way to do > >this. It's not like a fixmap slot costs anything. > > Otoh there are many fixmap slots not used under Xen, perhaps it would > be possible to use one of those... One slot certainly doesn't cost a lot, I don't have a problem with reserving one page for this. -Andi