From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=52757 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Pa98q-0001os-US for qemu-devel@nongnu.org; Tue, 04 Jan 2011 10:49:46 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Pa98k-0005Kx-HR for qemu-devel@nongnu.org; Tue, 04 Jan 2011 10:49:39 -0500 Received: from e31.co.us.ibm.com ([32.97.110.149]:38955) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Pa98j-0005JQ-Rq for qemu-devel@nongnu.org; Tue, 04 Jan 2011 10:49:38 -0500 Received: from d03relay01.boulder.ibm.com (d03relay01.boulder.ibm.com [9.17.195.226]) by e31.co.us.ibm.com (8.14.4/8.13.1) with ESMTP id p04FZER8023093 for ; Tue, 4 Jan 2011 08:35:14 -0700 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay01.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p04FnBlU169428 for ; Tue, 4 Jan 2011 08:49:14 -0700 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p04FnB0V030966 for ; Tue, 4 Jan 2011 08:49:11 -0700 Date: Tue, 4 Jan 2011 09:49:02 -0600 From: Ryan Harper Subject: Re: [Qemu-devel] Re: [PATCH] Fix segfault with ram_size > 4095M without kvm Message-ID: <20110104154902.GA30977@us.ibm.com> References: <20101208160110.1b0c7c64@doriath> <4CFFCD10.6060500@linux.vnet.ibm.com> <20101208162745.60d085db@doriath> <20101225223552.GA9076@volta.aurel32.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101225223552.GA9076@volta.aurel32.net> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Aurelien Jarno Cc: ryanh@linux.vnet.ibm.com, Anthony Liguori , qemu-devel@nongnu.org, Luiz Capitulino , Anthony Liguori , amit.shah@redhat.com * Aurelien Jarno [2010-12-25 16:37]: > On Wed, Dec 08, 2010 at 04:27:45PM -0200, Luiz Capitulino wrote: > > On Wed, 08 Dec 2010 12:23:12 -0600 > > Anthony Liguori wrote: > > > > > On 12/08/2010 12:01 PM, Luiz Capitulino wrote: > > > > Currently, x86_64-softmmu qemu segfaults when trying to use> 4095M memsize. > > > > This patch adds a simple check and error message (much like the 2047 limit on > > > > 32-bit hosts) on ram_size in the control path after we determine we're > > > > not using kvm > > > > > > > > Upstream qemu-kvm is affected if using the -no-kvm option; this patch address > > > > the segfault there as well. > > > > > > > > Signed-off-by: Ryan Harper > > > > Signed-off-by: Aurelien Jarno > > > > --- > > > > NOTE: this patch was applied in the v0.12.x branch, but it seems it got > > > > lost for master > > > > > > > > > > No, it was intentional. We should fix the segv, this is not a known > > > limitation but rather a bug. > > > > A TCG bug, I presume? > > > > Do you have more details about this issue and how to reproduce it? At the time of the bug, it was something simple like: qemu-system-x86_64 -m 4097 -hda /dev/null we'd get an imediate segfault. As you say, I'm not seeing it now on current git; I'll see about bisecting to see if we did get a fix for the issue. > > Support for more than 4GB of memory has been added a few years ago, > and I am not able to reproduce the problem anymore (I have booted a > 64-bit guest with 6GB of RAM, and make sure the guest use the whole > memory). I guess TCG itself is fine, but there might be a bug in > the MMU emulation in some cases. > > I also noticed that now i386-softmmu has been artificially limited to > 2047MB. Tthis configuration used to support up to 64GB of RAM (PAE) > on 64-bit hosts. > > -- > Aurelien Jarno GPG: 1024D/F1BCDB73 > aurelien@aurel32.net http://www.aurel33.net -- Ryan Harper Software Engineer; Linux Technology Center IBM Corp., Austin, Tx ryanh@us.ibm.com