From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: KVM crash on unusual PM->RM transition Date: Tue, 14 Apr 2009 19:16:33 +0300 Message-ID: <49E4B6E1.6020308@redhat.com> References: <49E3CDE1.8010001@zytor.com> <49E42260.7030009@zytor.com> <49E445C9.3000105@redhat.com> <49E4B046.5040008@zytor.com> <49E4B4BA.8010801@redhat.com> <49E4B581.4000808@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: "H. Peter Anvin" Return-path: Received: from mx2.redhat.com ([66.187.237.31]:34316 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755213AbZDNQP4 (ORCPT ); Tue, 14 Apr 2009 12:15:56 -0400 In-Reply-To: <49E4B581.4000808@zytor.com> Sender: kvm-owner@vger.kernel.org List-ID: H. Peter Anvin wrote: > Avi Kivity wrote: > >> - qemu doesn't do smp. >> >> > > It certainly claims to. > > Sorry, not specific enough: it doesn't do real SMP. Atomic instructions are translated as multiple, non-atomic instructions, so you can't run tcg compiled code in parallel. If your host is different than your target, you have memory ordering issues as well. What qemu does is to multiplex multiple guest cpus on one host thread. It's nice but it isn't how kvm works. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.