From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:34807) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T37ol-0008NZ-6Q for qemu-devel@nongnu.org; Sun, 19 Aug 2012 11:53:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1T37ok-0004Ns-AK for qemu-devel@nongnu.org; Sun, 19 Aug 2012 11:53:35 -0400 Received: from mail-vc0-f173.google.com ([209.85.220.173]:38618) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T37ok-0004No-6O for qemu-devel@nongnu.org; Sun, 19 Aug 2012 11:53:34 -0400 Received: by vcbgb23 with SMTP id gb23so4101373vcb.4 for ; Sun, 19 Aug 2012 08:53:33 -0700 (PDT) Date: Sun, 19 Aug 2012 11:53:32 -0400 From: Kevin O'Connor Message-ID: <20120819155332.GC12794@morn.localdomain> References: <50310119.4070806@redhat.com> <201208191634.50590.mbrown@fensystems.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201208191634.50590.mbrown@fensystems.co.uk> Subject: Re: [Qemu-devel] [ipxe-devel] Big real mode use in ipxe List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Michael Brown Cc: ipxe-devel@lists.ipxe.org, "seabios@seabios.org" , Avi Kivity , KVM list , qemu-devel On Sun, Aug 19, 2012 at 04:34:50PM +0100, Michael Brown wrote: > On Sunday 19 Aug 2012 16:07:05 Avi Kivity wrote: > > (and that seabios needs changes to either work in > > big real mode, or to put the processor back into big real mode after > > returning from a PMM service. > > If seabios switches into protected mode when performing a PMM service, then it > _must_ leave the segment limits at 4G when returning to real mode. To do > otherwise will violate the PMM spec, and will break conforming clients such as > iPXE. SeaBIOS does switch to 32bit mode during PMM calls and does switch to 16bit "big real" mode (segment limits set to 4G) on return. -Kevin