From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Raj, Ashok" Subject: Re: [PATCH v4 3/3] i386: publish advised value of MSR_IA32_FEATURE_CONTROL via fw_cfg Date: Fri, 17 Jun 2016 13:21:18 -0700 Message-ID: <20160617202118.GA8131@linux.intel.com> References: <20160616060621.30422-1-haozhong.zhang@intel.com> <20160616060621.30422-4-haozhong.zhang@intel.com> <20160616111951.yvmr6tznzw6tyxlx@hz-desktop> <603c703c-5142-4721-e5a3-2d147c32ccd1@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Haozhong Zhang , Paolo Bonzini , qemu-devel@nongnu.org, Richard Henderson , Eduardo Habkost , "Michael S . Tsirkin" , Marcelo Tosatti , kvm@vger.kernel.org, Boris Petkov , Tony Luck , Andi Kleen , rkrcmar@redhat.com, ashok.raj@intel.com To: Laszlo Ersek Return-path: Received: from mga02.intel.com ([134.134.136.20]:23025 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964833AbcFQUVl (ORCPT ); Fri, 17 Jun 2016 16:21:41 -0400 Content-Disposition: inline In-Reply-To: <603c703c-5142-4721-e5a3-2d147c32ccd1@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Fri, Jun 17, 2016 at 07:31:08PM +0200, Laszlo Ersek wrote: > >> > >> On 16/06/2016 08:06, Haozhong Zhang wrote: > >>> It's a prerequisite that certain bits of MSR_IA32_FEATURE_CONTROL should > >>> be set before some features (e.g. VMX and LMCE) can be used, which is > >>> usually done by the firmware. This patch adds a fw_cfg file > >>> "etc/msr_feature_control" which contains the advised value of > >>> MSR_IA32_FEATURE_CONTROL and can be used by guest firmware (e.g. SeaBIOS). > >>> I'm sorry i'm joining this discussion a bit late returning from vacation. In a real platform supporting LMCE, BIOS is responsible for setting the bits for IA32_FEATURE_CONTROL correctly. There are good reasons why we want the BIOS to play this role. in a virtualized environment, do we really have to push the same requirement or would it suffice to just emulate it as we did in the early patches. Not sure what exact problem is created by just simply supporting it within kvm/qemu and not needing the bios for the guest to also adapt these changes. Cheers, Ashok From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57675) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bE0Gw-00070a-AK for qemu-devel@nongnu.org; Fri, 17 Jun 2016 16:21:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bE0Gs-0004eJ-0N for qemu-devel@nongnu.org; Fri, 17 Jun 2016 16:21:45 -0400 Received: from mga02.intel.com ([134.134.136.20]:58451) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bE0Gr-0004dk-Py for qemu-devel@nongnu.org; Fri, 17 Jun 2016 16:21:41 -0400 Date: Fri, 17 Jun 2016 13:21:18 -0700 From: "Raj, Ashok" Message-ID: <20160617202118.GA8131@linux.intel.com> References: <20160616060621.30422-1-haozhong.zhang@intel.com> <20160616060621.30422-4-haozhong.zhang@intel.com> <20160616111951.yvmr6tznzw6tyxlx@hz-desktop> <603c703c-5142-4721-e5a3-2d147c32ccd1@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <603c703c-5142-4721-e5a3-2d147c32ccd1@redhat.com> Subject: Re: [Qemu-devel] [PATCH v4 3/3] i386: publish advised value of MSR_IA32_FEATURE_CONTROL via fw_cfg List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laszlo Ersek Cc: Haozhong Zhang , Paolo Bonzini , qemu-devel@nongnu.org, Richard Henderson , Eduardo Habkost , "Michael S . Tsirkin" , Marcelo Tosatti , kvm@vger.kernel.org, Boris Petkov , Tony Luck , Andi Kleen , rkrcmar@redhat.com, ashok.raj@intel.com On Fri, Jun 17, 2016 at 07:31:08PM +0200, Laszlo Ersek wrote: > >> > >> On 16/06/2016 08:06, Haozhong Zhang wrote: > >>> It's a prerequisite that certain bits of MSR_IA32_FEATURE_CONTROL should > >>> be set before some features (e.g. VMX and LMCE) can be used, which is > >>> usually done by the firmware. This patch adds a fw_cfg file > >>> "etc/msr_feature_control" which contains the advised value of > >>> MSR_IA32_FEATURE_CONTROL and can be used by guest firmware (e.g. SeaBIOS). > >>> I'm sorry i'm joining this discussion a bit late returning from vacation. In a real platform supporting LMCE, BIOS is responsible for setting the bits for IA32_FEATURE_CONTROL correctly. There are good reasons why we want the BIOS to play this role. in a virtualized environment, do we really have to push the same requirement or would it suffice to just emulate it as we did in the early patches. Not sure what exact problem is created by just simply supporting it within kvm/qemu and not needing the bios for the guest to also adapt these changes. Cheers, Ashok