From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thiemo Seufer Subject: Re: [Qemu-devel] Re: [PATCH 2 of 5] add can_dma/post_dma for direct IO Date: Tue, 23 Dec 2008 01:03:36 +0100 Message-ID: <20081223000336.GB16266@networkno.de> References: <20081213143944.GD30537@random.random> <4943E6F9.1050001@codemonkey.ws> <20081213165306.GE30537@random.random> <4944251D.8080109@codemonkey.ws> <20081214164751.GF30537@random.random> <49453BF2.9070304@redhat.com> <20081214171558.GH30537@random.random> <494565A1.6030306@redhat.com> <18767.50158.909778.205969@mariner.uk.xensource.com> <494FEE06.3040005@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andrea Arcangeli , chrisw@redhat.com, Gerd Hoffmann , kvm@vger.kernel.org To: qemu-devel@nongnu.org Return-path: Received: from relay01.mx.bawue.net ([193.7.176.67]:60756 "EHLO relay01.mx.bawue.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755526AbYLWADj (ORCPT ); Mon, 22 Dec 2008 19:03:39 -0500 Content-Disposition: inline In-Reply-To: <494FEE06.3040005@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity wrote: > Ian Jackson wrote: >> Avi Kivity writes ("[Qemu-devel] Re: [PATCH 2 of 5] add can_dma/post_dma for direct IO"): >> >>> Newer Xen shouldn't have this problem though; it runs qemu in kernel >>> mode in a dedicated 64-bit domain. >>> >> >> I think there is continued value in being able to emulate a guest >> whose physical address space exceeds the virtual address space in the >> host. The whole assumption that all guest accessible RAM is mapped at >> once, contiguously, is I think wrong. >> > > I agree that we shouldn't expect memory to be contiguous, in order to > properly support hotplug. But I see zero value in trying to support > large memory configurations on 32-bit in 2008. This is what 64-bit > systems are for! If Xen has a problem with 64-bit hosts, we can try to > accommodate it, but to have 32-bit qemu/tcg Running x86-64 binaries on a (non-x86) 32-bit host is IMHO quite an obvious application for qemu/tcg. > or qemu/kvm support large address spaces is pointless IMO. Interestingly, Virtualbox just started to support 64-bit-target-on-32-bit-host. Thiemo