From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=34786 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OOCP4-0000BI-V3 for qemu-devel@nongnu.org; Mon, 14 Jun 2010 12:20:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OOCP3-0001ok-U1 for qemu-devel@nongnu.org; Mon, 14 Jun 2010 12:20:50 -0400 Received: from mail-yw0-f190.google.com ([209.85.211.190]:65340) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OOCP3-0001oU-Pk for qemu-devel@nongnu.org; Mon, 14 Jun 2010 12:20:49 -0400 Received: by ywh28 with SMTP id 28so3274712ywh.28 for ; Mon, 14 Jun 2010 09:20:45 -0700 (PDT) Sender: Richard Henderson Message-ID: <4C1656C4.5090506@twiddle.net> Date: Mon, 14 Jun 2010 09:20:20 -0700 From: Richard Henderson MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 15/35] tcg-s390: Query instruction extensions that are installed. References: <1275678883-7082-1-git-send-email-rth@twiddle.net> <1275678883-7082-16-git-send-email-rth@twiddle.net> <20100610102815.GM26968@volta.aurel32.net> <4C1164ED.7020403@twiddle.net> <20100611080634.GP26968@volta.aurel32.net> <4C12368D.3050807@twiddle.net> <20100613104940.GA30341@volta.aurel32.net> <4C150120.2050600@twiddle.net> <20100613164412.GA17992@volta.aurel32.net> <75975F50-EEFE-43B8-B481-BC204E1817DC@suse.de> In-Reply-To: <75975F50-EEFE-43B8-B481-BC204E1817DC@suse.de> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: qemu-devel@nongnu.org, Aurelien Jarno On 06/13/2010 03:23 PM, Alexander Graf wrote: > On 13.06.2010, at 18:44, Aurelien Jarno wrote: >> Is KVM in 31-bit mode actually functional? > > I'm not aware of anything preventing it to be. But I honestly haven't > tried. As long as all hypercall parameters stay within the first > 32/31 bits, things should be safe. On the other hand, is there any point in supporting it? This does seem to be a case for which it does seem like having the extra VM space (KVM+TCG) and the extra register size (TCG) is extremely helpful. I'd be just as happy to adjust the configury to actively prevent compilation in 31-bit mode, rather than pretend it might work and never bother to test it... r~