From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber de Oliveira Costa Subject: Re: [PATCH 23/25] [PATCH] paravirt hooks for arch initialization Date: Fri, 10 Aug 2007 16:17:25 -0300 Message-ID: <46BCB9C5.4050103@redhat.com> References: <11865467522495-git-send-email-gcosta@redhat.com> <11865468394005-git-send-email-gcosta@redhat.com> <11865468431616-git-send-email-gcosta@redhat.com> <200708081144.04119.ak@suse.de> <46BB5258.8040609@goop.org> <20070809190303.214e5457@the-village.bc.nu> <5d6222a80708101108y62ebfa26n9f47bfc52b48f4a8@mail.gmail.com> <46BCB3A5.8090504@goop.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <46BCB3A5.8090504@goop.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Jeremy Fitzhardinge Cc: lguest@ozlabs.org, Steven@smtp2.linux-foundation.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, chrisw@sous-sol.org, anthony@codemonkey.ws, akpm@linux-foundation.org, mingo@elte.hu, Alan Cox List-Id: virtualization@lists.linuxfoundation.org Jeremy Fitzhardinge escreveu: > Glauber de Oliveira Costa wrote: >> On 8/9/07, Alan Cox wrote: >> >>>> What's the EBDA actually used for? The only place which seems to use >>>> ebda_addr is in the e820 code to avoid that area as RAM. >>>> >>> It belongs to the firmware. >>> >> Wouldn't it be better, then, to just skip this step unconditionally if >> we are running a paravirtualized guest? What do we from doing it? >> > > It's better to make discover_ebda() quietly cope with a missing ebda for > whatever reason. We could add an explicit interface to paravirt_ops to > handle this one little corner, but it isn't very important, not very > general and really its just clutter. Its much better to have things > cope with being virtualized quietly on their own rather than hit them > all with the pv_ops hammer. pv_ops is really for things where the > hypervisor-specific code really has to get actively involved. > I think the idea you gave me earlier of using probe_kernel_address could work. Xen/lguest/put_yours_here that won't use an ebda would then have to unmap the page, to make sure a read would fault.