From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1KILs0-0001rl-OK for qemu-devel@nongnu.org; Mon, 14 Jul 2008 07:05:28 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1KILrw-0001rW-8n for qemu-devel@nongnu.org; Mon, 14 Jul 2008 07:05:27 -0400 Received: from [199.232.76.173] (port=36888 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1KILrw-0001rB-3f for qemu-devel@nongnu.org; Mon, 14 Jul 2008 07:05:24 -0400 Received: from mx1.redhat.com ([66.187.233.31]:38207) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1KILrv-0006uP-H2 for qemu-devel@nongnu.org; Mon, 14 Jul 2008 07:05:23 -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 m6EB5A7V031297 for ; Mon, 14 Jul 2008 07:05:10 -0400 Received: from file.fab.redhat.com (file.fab.redhat.com [10.33.63.6]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id m6EB59MA005391 for ; Mon, 14 Jul 2008 07:05:09 -0400 Received: (from berrange@localhost) by file.fab.redhat.com (8.13.1/8.13.1/Submit) id m6EB58UR015666 for qemu-devel@nongnu.org; Mon, 14 Jul 2008 12:05:08 +0100 Date: Mon, 14 Jul 2008 12:05:08 +0100 From: "Daniel P. Berrange" Subject: Re: [Qemu-devel] [RFC][PATCH] x86: Optional segment type and limit checks - v2 Message-ID: <20080714110507.GD29536@redhat.com> References: <4874AB47.9090208@siemens.com> <487B2BC8.9050804@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <487B2BC8.9050804@siemens.com> Reply-To: "Daniel P. Berrange" , 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 On Mon, Jul 14, 2008 at 12:34:48PM +0200, Jan Kiszka wrote: > This is the second version of my segment type and register check. It > reduces the impact on the translator code significantly, and it also > fixes a bug of the "size" helper variant in the previous version. > > The idea of this patch is to generate calls to a check helper only in > case the user requested this support via "-seg-checks". This feature > remains off by default as most x86 OSes do not care about protection via > segmentation anymore (and it was even removed from 64-bit modes by the > CPU vendors). Two current users of protection via segmentation I know of - 32-bit linux with the ExecShield capability will still use segmentation to split the address space into executable vs non-executable regions, if the CPU doesn't have NX bit support. - 32-bit Xen uses segmentation for protecting the hypervisor. Regards, Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|