From mboxrd@z Thu Jan 1 00:00:00 1970 From: "James Harper" Subject: RE: Ideas for PV on SeaBIOS Date: Thu, 19 May 2011 19:32:04 +1000 Message-ID: References: <4DD4EC2502000078000420F7@vpn.id2.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Return-path: Content-class: urn:content-classes:message In-Reply-To: <4DD4EC2502000078000420F7@vpn.id2.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 , Daniel Castro Cc: xen-devel@lists.xensource.com, seabios@seabios.org List-Id: xen-devel@lists.xenproject.org >=20 > >>> On 19.05.11 at 07:33, Daniel Castro wrote: > > In order to give PV Drivers to SeaBIOS we will need to solve a few > > problems, one is the following: > > Does a booting kernel informs the BIOS that it will leave real mode > > and not use it again? When the booting kernel uses CPU real mode for > > the last time, how can we (Xen or SeaBIOS) know that real mode will no > > longer be used, and hence BIOS calls will not be issued? > > We want upon last real mode usage to leave all Xen PV information in a > > clean state, this means, closing the channel and ring between the > > newly created domain and the host system. >=20 > How can you be certain an OS won't switch back to real mode even > after an extended period of up-time? Or that such switching back > would affect you (could be calling e.g. the video or PCI BIOS > functions only). Well that's a problem with any device with a real mode counterpart (eg INT13 for storage) isn't it? so just handle it in the same way. James