From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=45655 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OQKqh-0000sw-2h for qemu-devel@nongnu.org; Sun, 20 Jun 2010 09:46:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OQKqg-0007wQ-1D for qemu-devel@nongnu.org; Sun, 20 Jun 2010 09:46:10 -0400 Received: from mail2.shareable.org ([80.68.89.115]:46229) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OQKqf-0007wK-SG for qemu-devel@nongnu.org; Sun, 20 Jun 2010 09:46:10 -0400 Date: Sun, 20 Jun 2010 14:46:03 +0100 From: Jamie Lokier Subject: Re: [Qemu-devel] [Bug 596106] Re: kvm to emulate 64 bit cpu on 32 bit host Message-ID: <20100620134603.GC15818@shareable.org> References: <27050726.2281276981848303.JavaMail.acathrow@aic-desktop.cathrow.org> <82AFD1E1-29B1-4DDF-B1F3-3B3EB98C13BB@claunia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <82AFD1E1-29B1-4DDF-B1F3-3B3EB98C13BB@claunia.com> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Natalia Portillo Cc: Bug 596106 <596106@bugs.launchpad.net>, Andrew Cathrow , qemu-devel@nongnu.org Natalia Portillo wrote: > You got the point wrong, I'm talking running WITH 64 bit hardware in a > 32 bit guest. > This is done in Mac OS X Leopard (kernel is only 32 bit) and Mac OS X > Snow Leopard (using 32 bit kernel not 64 bit one) by VMWare, Parallels > and VirtualBox, as well as on Windows 32 bit using VMWare (dunno about > VBox and Parallels, VirtualPC is unable to run 64 bit guests at all > even on 64 bit hosts), just provided of course, the hardware is 64 > bit. Ah yes, Mac OS X too. Apart from breaking userspace, the other reason people stick with 32-bit host kernels on both Windows and Macs is the 64-bit device drivers often don't work properly, or aren't available at all. They continue to improve, but still aren't as mature and dependable as 32-bit drivers. This is also true of Linux 64-bit kernels - both bugs and unavailable third party drivers/firmware. (But less so than the other OSes.) So even with Linux people cannot assume dropping in a 64-bit host kernel is always free of kernel/driver issues. Marking this feature request "won't fix" is just a statement that KVM developers aren't inclined to support this feature. But there's nothing to stop an interested contributor having a go. I'm sure if it works and the code is clean enough it will be accepted. > VirtualPC is unable to run 64 bit guests at all even on 64 bit > hosts Are you sure? Microsoft provides numerous downloadable 64-bit guest Windows images, and VirtualPC is Microsoft's; they must be running on something. -- Jamie