From patchwork Thu Mar 4 21:27:24 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Aurelien Jarno X-Patchwork-Id: 46980 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [199.232.76.165]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 0E90FB7D08 for ; Fri, 5 Mar 2010 08:31:49 +1100 (EST) Received: from localhost ([127.0.0.1]:42506 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NnIe2-0002CC-AZ for incoming@patchwork.ozlabs.org; Thu, 04 Mar 2010 16:31:46 -0500 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NnIZy-0005WK-5X for qemu-devel@nongnu.org; Thu, 04 Mar 2010 16:27:34 -0500 Received: from [199.232.76.173] (port=52937 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NnIZx-0005V8-Fh for qemu-devel@nongnu.org; Thu, 04 Mar 2010 16:27:33 -0500 Received: from Debian-exim by monty-python.gnu.org with spam-scanned (Exim 4.60) (envelope-from ) id 1NnIZv-0002qx-GB for qemu-devel@nongnu.org; Thu, 04 Mar 2010 16:27:33 -0500 Received: from hall.aurel32.net ([88.191.82.174]:39274) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1NnIZv-0002q7-4c for qemu-devel@nongnu.org; Thu, 04 Mar 2010 16:27:31 -0500 Received: from aurel32 by hall.aurel32.net with local (Exim 4.69) (envelope-from ) id 1NnIZo-0000le-KX; Thu, 04 Mar 2010 22:27:24 +0100 Date: Thu, 4 Mar 2010 22:27:24 +0100 From: Aurelien Jarno To: Ryan Harper Subject: Re: [Qemu-devel] [PATCH] Fix segfault with ram_size > 4095M without kvm Message-ID: <20100304212724.GH5860@hall.aurel32.net> References: <20100223151314.GN17350@us.ibm.com> <4B840A17.9050809@aurel32.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <4B840A17.9050809@aurel32.net> X-Mailer: Mutt 1.5.18 (2008-05-17) User-Agent: Mutt/1.5.18 (2008-05-17) X-detected-operating-system: by monty-python.gnu.org: GNU/Linux 2.6 (newer, 3) Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org On Tue, Feb 23, 2010 at 06:02:15PM +0100, Aurelien Jarno wrote: > Ryan Harper a écrit : > > 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. > > It looks like workarounding the real bug. At some point both > i386-softmmu (via PAE) and x86_64-softmmu were able to support > 4GB of > memory. I remember adding the support long time ago, and testing it with > 32GB of emulated RAM. I have looked into that, and actually one patch to get full support for > 4GB of memory was not merged: While this patch is acceptable for qemu i386, it creates a big L1 table for x86_64 or other 64-bit architectures, resulting in huge memory overhead. The recent multilevel tables patches from Richard Henderson should fix the problem for HEAD (I haven't found time to look at them in details). As this is not something we really want to backport, your patch makes sense in stable-0.12. > > Signed-off-by: Ryan Harper > > --- > > vl.c | 6 ++++++ > > 1 files changed, 6 insertions(+), 0 deletions(-) > > > > diff --git a/vl.c b/vl.c > > index db7a178..a659e98 100644 > > --- a/vl.c > > +++ b/vl.c > > @@ -5760,6 +5760,12 @@ int main(int argc, char **argv, char **envp) > > fprintf(stderr, "failed to initialize KVM\n"); > > exit(1); > > } > > + } else { > > + /* without kvm enabled, we can only support 4095 MB RAM */ > > + if (ram_size > (4095UL << 20)) { > > + fprintf(stderr, "qemu: without kvm support at most 4095 MB RAM can be simulated\n"); > > + exit(1); > > + } > > } > > > > if (qemu_init_main_loop()) { > > > -- > Aurelien Jarno GPG: 1024D/F1BCDB73 > aurelien@aurel32.net http://www.aurel32.net > > > diff --git a/exec.c b/exec.c index 8389c54..b0bb058 100644 --- a/exec.c +++ b/exec.c @@ -166,7 +166,7 @@ typedef struct PhysPageDesc { */ #define L1_BITS (TARGET_VIRT_ADDR_SPACE_BITS - L2_BITS - TARGET_PAGE_BITS) #else -#define L1_BITS (32 - L2_BITS - TARGET_PAGE_BITS) +#define L1_BITS (TARGET_PHYS_ADDR_SPACE_BITS - L2_BITS - TARGET_PAGE_BITS) #endif #define L1_SIZE (1 << L1_BITS)