From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH][RFC] Emulating real mode with x86_emulate Date: Fri, 30 Mar 2007 17:00:54 -0500 Message-ID: <460D8896.9050606@us.ibm.com> References: <4607074E.1030807@us.ibm.com> <460D7F26.2080809@us.ibm.com> <20070330212548.GA10338@one.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20070330212548.GA10338@one.firstfloor.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Andi Kleen Cc: xen-devel@lists.xensource.com, Keir Fraser , "Nakajima, Jun" List-Id: xen-devel@lists.xenproject.org Andi Kleen wrote: >> There are some hard problems with migrating into QEMU. Namely, the code >> that QEMU generates isn't SMP safe (atomic instructions lose their >> atomicity) >> > > I see. > > You're worrying that real mode startup trampolines of OS rely > on atomic instructions? I can't think of much other possible real mode > multi CPU code. > No, that's a concern for using V2E to handle 32 bit code. The big problem for handling real mode code is dealing with synchronization for device state. With the devices split between QEMU and within the hypervisor, this becomes even more complicated. Any of the interesting guests that use big real mode also depend on being able to synchronize this device state. Regards, Anthony Liguori > -Andi >