From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43640) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZyHyb-00087J-QS for qemu-devel@nongnu.org; Mon, 16 Nov 2015 06:29:38 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZyHyW-00027K-My for qemu-devel@nongnu.org; Mon, 16 Nov 2015 06:29:37 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:47865) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZyHyW-00026x-FK for qemu-devel@nongnu.org; Mon, 16 Nov 2015 06:29:32 -0500 Received: from localhost by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 16 Nov 2015 04:29:30 -0700 Message-ID: <5649BE12.1060001@linux.vnet.ibm.com> Date: Mon, 16 Nov 2015 16:59:22 +0530 From: Aravinda Prasad MIME-Version: 1.0 References: <20151111171135.4328.41819.stgit@aravindap> <20151111171602.4328.34006.stgit@aravindap> <56444957.9080003@redhat.com> <20151116035046.GA19340@iris.ozlabs.ibm.com> <56499B65.6050601@redhat.com> In-Reply-To: <56499B65.6050601@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 4/4] target-ppc: Handle NMI guest exit List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Huth Cc: benh@au1.ibm.com, aik@ozlabs.ru, agraf@suse.de, qemu-devel@nongnu.org, Paul Mackerras , qemu-ppc@nongnu.org, sam.bobroff@au1.ibm.com, david@gibson.dropbear.id.au On Monday 16 November 2015 02:31 PM, Thomas Huth wrote: > On 16/11/15 04:50, Paul Mackerras wrote: >> On Thu, Nov 12, 2015 at 09:09:59AM +0100, Thomas Huth wrote: >>> >>> Shouldn't you also check MSR_ME here first and enter checkstop when >>> machine checks are disabled? >> >> MSR_ME is a hypervisor resource and is not able to be controlled by HV >> KVM guests, or in fact by the OS running on the pseries machine target >> regardless of how it's accelerated or emulated. >> >> What you say would only apply if we had a powernv machine target and >> we were emulating the whole system, and in that case we wouldn't be >> using any hcalls, and we wouldn't be doing FWNMI (or at least not at >> this level). >> >> So the answer is no, MSR_ME will always be set when running in a >> guest, and we don't ever need to checkstop the virtual machine. > > Good point, I missed that sentence about the hypervisor resource in the > PowerISA. So QEMU does not have to check this bit here. > > But out of curiosity: What happens if a guest disables the ME bit? Is > this checked somewhere or simply ignored? If a guest disables the ME bit (and may be does not set it again) and should a machine check happen in guest address space then the entire system checkstops? However, I am not sure if the guest is allowed to disable ME bit. Regards, Aravinda > > Thomas > -- Regards, Aravinda