From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NKH7U-0003Hn-QS for qemu-devel@nongnu.org; Mon, 14 Dec 2009 15:02:12 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NKH7Q-0003Go-Ud for qemu-devel@nongnu.org; Mon, 14 Dec 2009 15:02:12 -0500 Received: from [199.232.76.173] (port=37129 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NKH7Q-0003Gl-N3 for qemu-devel@nongnu.org; Mon, 14 Dec 2009 15:02:08 -0500 Received: from mail-iw0-f197.google.com ([209.85.223.197]:54624) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NKH7Q-0005eJ-7c for qemu-devel@nongnu.org; Mon, 14 Dec 2009 15:02:08 -0500 Received: by iwn35 with SMTP id 35so2242240iwn.4 for ; Mon, 14 Dec 2009 12:02:07 -0800 (PST) Message-ID: <4B2699BB.1090302@codemonkey.ws> Date: Mon, 14 Dec 2009 14:02:03 -0600 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] cpuid problem in upstream qemu with kvm References: <20091214193541.GA6150@redhat.com> <4B269596.1050103@codemonkey.ws> <20091214194432.GC6150@redhat.com> <4B2698A9.9090107@codemonkey.ws> <20091214200002.GA27769@redhat.com> In-Reply-To: <20091214200002.GA27769@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gleb Natapov Cc: avi@redhat.com, qemu-devel@nongnu.org, "Michael S. Tsirkin" Gleb Natapov wrote: >> I thought KVM emulates the syscall instruction? I swear I've seen >> patches for that. >> >> > It is. Starting from 2.6.32. > Okay, so this is a performance vs. migration compatibility issue then? BTW, couldn't we just not advertise syscall in cpuid? That should fix it too without sacrificing migration compatibility. We get a slight slowdown on AMD hosts but that's probably minor compared to the cost of using emulated syscall on Intel hosts. Regards, Anthony Liguori