From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=41569 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PWcik-0003DD-Lp for qemu-devel@nongnu.org; Sat, 25 Dec 2010 17:36:15 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PWcij-0008Rg-Hm for qemu-devel@nongnu.org; Sat, 25 Dec 2010 17:36:14 -0500 Received: from hall.aurel32.net ([88.191.126.93]:55236) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PWcij-0008Ra-9C for qemu-devel@nongnu.org; Sat, 25 Dec 2010 17:36:13 -0500 Date: Sat, 25 Dec 2010 23:35:52 +0100 From: Aurelien Jarno Message-ID: <20101225223552.GA9076@volta.aurel32.net> References: <20101208160110.1b0c7c64@doriath> <4CFFCD10.6060500@linux.vnet.ibm.com> <20101208162745.60d085db@doriath> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20101208162745.60d085db@doriath> Subject: [Qemu-devel] Re: [PATCH] Fix segfault with ram_size > 4095M without kvm List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Luiz Capitulino Cc: ryanh@linux.vnet.ibm.com, Anthony Liguori , Anthony Liguori , amit.shah@redhat.com, qemu-devel@nongnu.org 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? 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