From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] [PATCH v3 01/39] virtio-pci: get config on init Date: Mon, 08 Aug 2011 08:02:08 -0500 Message-ID: <4E3FDE50.3060702@codemonkey.ws> References: <1312463195-13605-1-git-send-email-avi@redhat.com> <1312463195-13605-2-git-send-email-avi@redhat.com> <4E3BF599.4050207@codemonkey.ws> <20110808103606.GA10372@redhat.com> <4E3FDA5F.5050105@codemonkey.ws> <20110808125647.GA27643@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Avi Kivity , kvm@vger.kernel.org, qemu-devel@nongnu.org To: "Michael S. Tsirkin" Return-path: Received: from mail-pz0-f42.google.com ([209.85.210.42]:54209 "EHLO mail-pz0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751982Ab1HHNCM (ORCPT ); Mon, 8 Aug 2011 09:02:12 -0400 Received: by pzk37 with SMTP id 37so8283210pzk.1 for ; Mon, 08 Aug 2011 06:02:11 -0700 (PDT) In-Reply-To: <20110808125647.GA27643@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 08/08/2011 07:56 AM, Michael S. Tsirkin wrote: > On Mon, Aug 08, 2011 at 07:45:19AM -0500, Anthony Liguori wrote: >> On 08/08/2011 05:36 AM, Michael S. Tsirkin wrote: >>>> Thinking more closely, I don't think this right. >>>> >>>> Updating on map ensured that the config was refreshed after each >>>> time the bar was mapped. In the very least, the config needs to be >>>> refreshed during reset because the guest may write to the guest >>>> space which should get cleared after reset. >>>> >>>> Regards, >>>> >>>> Anthony Liguori >>> >>> Not sure I understand. Which register, for example, >>> do you have in mind? >>> Could you clarify please? >> >> Actually, you never need to call config_get() AFAICT. It's called >> in every read/write access. > > Every read, yes. But every write? Are you sure? Yeah, not on write, but I think this is a bug. get_config() should be called before doing the memcpy() in order to have a proper RMW. Regards, Anthony Liguori > >> So I think the code you changed is >> extraneous now. >> >> Regards, >> >> Anthony Liguori > >