From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1KVVKN-0006M9-0i for qemu-devel@nongnu.org; Tue, 19 Aug 2008 13:49:07 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1KVVKM-0006Lf-5F for qemu-devel@nongnu.org; Tue, 19 Aug 2008 13:49:06 -0400 Received: from [199.232.76.173] (port=34003 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1KVVKL-0006LW-W9 for qemu-devel@nongnu.org; Tue, 19 Aug 2008 13:49:06 -0400 Received: from mx1.redhat.com ([66.187.233.31]:38846) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1KVVKM-0007k3-D1 for qemu-devel@nongnu.org; Tue, 19 Aug 2008 13:49:06 -0400 Received: from int-mx1.corp.redhat.com (int-mx1.corp.redhat.com [172.16.52.254]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id m7JHmwp8030574 for ; Tue, 19 Aug 2008 13:48:58 -0400 Received: from localhost.localdomain (vpn-13-69.rdu.redhat.com [10.11.13.69]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id m7JHmtla019263 for ; Tue, 19 Aug 2008 13:48:56 -0400 Message-ID: <48AB070A.1040104@redhat.com> Date: Tue, 19 Aug 2008 19:46:50 +0200 From: Chris Lalancette MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Bug with TARGET_PHYS_ADDR_SPACE_BITS Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Hello, oVirt is currently using straight x86_64 qemu emulation for certain parts of the architecture (we mostly use KVM, but need to use full emulation for a couple of parts). We recently upgraded our userspace package to kvm-72, but found that we could not PXE boot guests when we were doing full emulation (under kvm, we could PXE boot just fine). We also tried using qemu SVN tip, with similar results. We ended up doing a bisect, and tracked down the problem to this commit (from the kvm repo, but pulled from qemu): http://git.kernel.org/?p=linux/kernel/git/amit/kvm-userspace.git;a=commit;h=468f7507339a5236bff8ab339eb0c1b019a95fda The important changes in there in terms of this bug revolves around TARGET_PHYS_ADDR_SPACE_BITS in exec.c. If I change that back to 32 (what it was before this patch for x86_64), the PXE boot succeeds. Also, if I remove TARGET_PHYS_ADDR_SPACE_BITS > 32 conditional code in phys_page_find_alloc(), but leave TARGET_PHYS_ADDR_SPACE_BITS as 42, the PXE boot also works. I can't claim to understand the conditional code I've compiled out, so I'm not sure where the bug would be. Does anyone have an idea what the problem might be? Thanks, Chris Lalancette