From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39597) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dfkgB-00072s-0m for qemu-devel@nongnu.org; Thu, 10 Aug 2017 06:27:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dfkg7-00087v-7r for qemu-devel@nongnu.org; Thu, 10 Aug 2017 06:27:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37586) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dfkg7-00087D-1o for qemu-devel@nongnu.org; Thu, 10 Aug 2017 06:26:59 -0400 Date: Thu, 10 Aug 2017 11:26:49 +0100 From: "Daniel P. Berrange" Message-ID: <20170810102649.GF12980@redhat.com> Reply-To: "Daniel P. Berrange" References: <1502359687-25370-1-git-send-email-tianyu.lan@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1502359687-25370-1-git-send-email-tianyu.lan@intel.com> Subject: Re: [Qemu-devel] [PATCH] x86: Increase max vcpu number to 352 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Lan Tianyu Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, rth@twiddle.net, ehabkost@redhat.com, mst@redhat.com On Thu, Aug 10, 2017 at 06:08:07PM +0800, Lan Tianyu wrote: > Intel Xeon phi chip will support 352 logical threads. For HPC > usage case, it will create a huge VM with vcpus number as same as host > cpus. This patch is to increase max vcpu number to 352. If we pick arbitray limits based on size of physical CPUs that happen to be shipping today, we'll continue the cat+mouse game forever trailing latest CPUs that vendors ship. IMHO we should pick a higher number influenced by technical constraints of the q35 impl instead. eg can we go straight to something like 512 or 1024 ? > Signed-off-by: Lan Tianyu > --- > hw/i386/pc_q35.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c > index 169a214..5e93749 100644 > --- a/hw/i386/pc_q35.c > +++ b/hw/i386/pc_q35.c > @@ -299,7 +299,7 @@ static void pc_q35_machine_options(MachineClass *m) > m->default_display = "std"; > m->no_floppy = 1; > m->has_dynamic_sysbus = true; > - m->max_cpus = 288; > + m->max_cpus = 352; > } You'll need to introduce machine type back compat support so that we avoid changing the 2.10 q35 machine type - only the 2.11 machine type should have the new limit. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|