From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guillaume Thouvenin Subject: [RFC] change provided physical RAM map to add EBDA Date: Wed, 14 Mar 2007 11:02:38 +0000 Message-ID: <20070314110238.GA27518@bull.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Xen devel ML List-Id: xen-devel@lists.xenproject.org Hello When dom0 starts, we can see that Xen is provided a uniform pseudo physical RAM map. For example for a dom0 with 1GB of RAM we can see: BIOS-provided physical RAM map: Xen: 0000000000000000 - 0000000040800000 (usable) If I need to use data provided by EBDA, is it possible to change how Xen provides information to dom0? My idea was to provide something like this: BIOS-provided physical RAM map: Xen: 0000000000000000 - 0000000000099000 (usable) Xen: 0000000000099000 - 00000000000a0000 (reserved for EBDA) Xen: 00000000000a0000 - 0000000040800000 (usable) where memory from 99000 to a0000 is a direct mapping to machine address. By doing this, dom0 will be able to access the extended BIOS data area. This will allow to port pieces of code that are using EBDA area. I'm thinking about MP-table parsing routines found in arch/i386/kernel/mpparse.c or IBM summit code found in arch/i386/kernel/summit.c. Also we can see in arch/x86_64/kernel/setup-xen.c that currently the code that deals with ebda is just removed. Does it make sense to add support for EBDA in dom0 by changing the physical map? If not, what is the more appropriate solution to get information found in EBDA area from dom0? Regards, Guillaume