From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: Configuration vs. compat hints [was Re: [Qemu-devel] [PATCHv3 03/13] qemu: add routines to manage PCI capabilities] Date: Sun, 14 Jun 2009 12:47:54 +0300 Message-ID: <20090614094754.GC6959@redhat.com> References: <20090610150129.GC28601@redhat.com> <200906101624.30659.paul@codesourcery.com> <20090610174301.GC7416@shareable.org> <20090610182227.GN28601@redhat.com> <20090610192702.GH7416@shareable.org> <1244796209.16425.20.camel@blaa> <4A326C7E.3020309@codemonkey.ws> <1244822007.30522.68.camel@blaa> <20090614093411.GA6959@redhat.com> <4A34C4C9.8030105@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Mark McLoughlin , Anthony Liguori , Jamie Lokier , Carsten Otte , kvm@vger.kernel.org, Glauber Costa , Rusty Russell , qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, Blue Swirl , Christian Borntraeger , Paul Brook To: Avi Kivity Return-path: Received: from mx2.redhat.com ([66.187.237.31]:39104 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751373AbZFNJuV (ORCPT ); Sun, 14 Jun 2009 05:50:21 -0400 Content-Disposition: inline In-Reply-To: <4A34C4C9.8030105@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Sun, Jun 14, 2009 at 12:37:13PM +0300, Avi Kivity wrote: > Michael S. Tsirkin wrote: >> >> If we want to remove a device from under a running guest, you need >> hotplug. So we can't just remove several lines from the config and hope >> that it'll work simply because the PCI address is stable. >> > > Why not? E.g. configuration cycles address a specific bus/slot. You need cooperation from guest if you want to move a device. >> OTOH, if you reboot the guest, it's ok for addresses to change. >> > > No, it's not. Some guests depend on addressing for their configuration > (for example older Linux guests will swap eth0/eth1 if you swap their > slots). Ah, I misunderstood what's meant by the address. I agree that it's useful to be able to control device's placement on the bus. -- MST From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MFmM3-0002OT-Lc for qemu-devel@nongnu.org; Sun, 14 Jun 2009 05:50:23 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MFmLy-0002NN-Cz for qemu-devel@nongnu.org; Sun, 14 Jun 2009 05:50:22 -0400 Received: from [199.232.76.173] (port=37229 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MFmLy-0002NJ-6d for qemu-devel@nongnu.org; Sun, 14 Jun 2009 05:50:18 -0400 Received: from mx2.redhat.com ([66.187.237.31]:44574) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1MFmLx-0004Cz-KV for qemu-devel@nongnu.org; Sun, 14 Jun 2009 05:50:17 -0400 Date: Sun, 14 Jun 2009 12:47:54 +0300 From: "Michael S. Tsirkin" Subject: Re: Configuration vs. compat hints [was Re: [Qemu-devel] [PATCHv3 03/13] qemu: add routines to manage PCI capabilities] Message-ID: <20090614094754.GC6959@redhat.com> References: <20090610150129.GC28601@redhat.com> <200906101624.30659.paul@codesourcery.com> <20090610174301.GC7416@shareable.org> <20090610182227.GN28601@redhat.com> <20090610192702.GH7416@shareable.org> <1244796209.16425.20.camel@blaa> <4A326C7E.3020309@codemonkey.ws> <1244822007.30522.68.camel@blaa> <20090614093411.GA6959@redhat.com> <4A34C4C9.8030105@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A34C4C9.8030105@redhat.com> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: Mark McLoughlin , kvm@vger.kernel.org, Carsten Otte , Glauber Costa , Rusty Russell , qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, Blue Swirl , Christian Borntraeger , Paul Brook On Sun, Jun 14, 2009 at 12:37:13PM +0300, Avi Kivity wrote: > Michael S. Tsirkin wrote: >> >> If we want to remove a device from under a running guest, you need >> hotplug. So we can't just remove several lines from the config and hope >> that it'll work simply because the PCI address is stable. >> > > Why not? E.g. configuration cycles address a specific bus/slot. You need cooperation from guest if you want to move a device. >> OTOH, if you reboot the guest, it's ok for addresses to change. >> > > No, it's not. Some guests depend on addressing for their configuration > (for example older Linux guests will swap eth0/eth1 if you swap their > slots). Ah, I misunderstood what's meant by the address. I agree that it's useful to be able to control device's placement on the bus. -- MST