From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57555) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WSqgk-0008CN-PQ for qemu-devel@nongnu.org; Wed, 26 Mar 2014 12:28:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WSqge-00020T-R0 for qemu-devel@nongnu.org; Wed, 26 Mar 2014 12:28:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:61160) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WSqge-00020L-H9 for qemu-devel@nongnu.org; Wed, 26 Mar 2014 12:28:20 -0400 Message-ID: <5333001F.90805@redhat.com> Date: Wed, 26 Mar 2014 17:28:15 +0100 From: Laszlo Ersek MIME-Version: 1.0 References: <20140326064510.5518.72436.malonedeb@chaenomeles.canonical.com> <20140326064510.5518.72436.malonedeb@chaenomeles.canonical.com> <20140326103112.GA20219@redhat.com> <5332C7D2.3030901@redhat.com> <20140326125828.GA2192@redhat.com> <20140326144829.52f72b74@nial.usersys.redhat.com> <20140326145431.GA3269@redhat.com> <20140326150638.GR2057@otherpad.lan.raisama.net> <20140326150929.GA3511@redhat.com> <20140326152323.GS2057@otherpad.lan.raisama.net> In-Reply-To: <20140326152323.GS2057@otherpad.lan.raisama.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [Bug 1297651] [NEW] KVM create a win7 guest with Qemu, it boots up fail List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost , "Michael S. Tsirkin" Cc: Igor Mammedov , Bug 1297651 <1297651@bugs.launchpad.net>, qemu-devel@nongnu.org, robert.hu@intel.com On 03/26/14 16:23, Eduardo Habkost wrote: > On Wed, Mar 26, 2014 at 05:09:29PM +0200, Michael S. Tsirkin wrote: >> On Wed, Mar 26, 2014 at 12:06:38PM -0300, Eduardo Habkost wrote: >>> On Wed, Mar 26, 2014 at 04:54:31PM +0200, Michael S. Tsirkin wrote: >>>> On Wed, Mar 26, 2014 at 02:48:29PM +0100, Igor Mammedov wrote: >>> [...] >>>>> more clean would be to abort if CPON index (i.e. APIC ID) >>>>> is more than 255. That would affect small number of weird >>>>> topologies but sould be fine for most usecases. >>>> >>>> Any idea how to trigger this behaviour? >>> >>> Set sockets and/or cores to a 2^n+1 value. It will use n+1 bits for the >>> socket ID and core ID, making APIC ID larger than CPU index. You can get >>> a very large APIC ID if you use, for example: >>> >>> -smp 1,cores=17,threads=17,maxcpus=200 >>> >>> There's code to limit the maximum APIC ID and abort if it is too large, >>> already (so the above command-line will make QEMU abort). >> >> Okay so how do you make this package size exactly 256? > > I didn't look for a proof yet, but it looks like having apic_id_limit > exactly 256 while max_cpus <= 255 is impossible. > > Laszlo, did you find a case where this was possible? No, it's impossible, like you say; see my other email with the small program doing an exhaustive search. Any topology that simultaneously results in: - a maximal VCPU count <= 255, and - an APIC ID width <= 8 will prevent the exact APIC ID value 255. Thanks Laszlo