From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: [Qemu-devel] Using PCI config space to indicate config location Date: Wed, 10 Oct 2012 14:14:47 +1030 Message-ID: <87txu36le8.fsf@rustcorp.com.au> References: <874nmajcmj.fsf@codemonkey.ws> <87y5jhpuu2.fsf@rustcorp.com.au> <87bogddq0l.fsf@codemonkey.ws> <5072EA14.30809@redhat.com> <87k3v1gfw1.fsf@codemonkey.ws> <507333F1.1060000@redhat.com> <874nm4u1in.fsf@codemonkey.ws> <87sj9o8qn7.fsf@rustcorp.com.au> <87sj9oh0pm.fsf@codemonkey.ws> <87haq48hds.fsf@rustcorp.com.au> <20121009210901.GY14867@jl-vm1.vm.bytemark.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20121009210901.GY14867@jl-vm1.vm.bytemark.co.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Jamie Lokier Cc: Anthony Liguori , kvm@vger.kernel.org, "Michael S. Tsirkin" , qemu-devel , virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org Jamie Lokier writes: > Rusty Russell wrote: >> I don't think it'll be that bad; reset clears the device to unknown, >> bar0 moves it from unknown->legacy mode, bar1/2/3 changes it from >> unknown->modern mode, and anything else is bad (I prefer being strict so >> we catch bad implementations from the beginning). > > Will that work, if the guest with kernel that uses modern mode, kexecs > to an older (but presumed reliable) kernel that only knows about legacy mode? > > I.e. will the replacement kernel, or (ideally) replacement driver on > the rare occasion that is needed on a running kernel, be able to reset > the device hard enough? Well, you need to reset the device, so yes. Cheers, Rusty. From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:53785) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TLt7S-00067y-WA for qemu-devel@nongnu.org; Wed, 10 Oct 2012 06:02:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TLt7O-0003xk-OZ for qemu-devel@nongnu.org; Wed, 10 Oct 2012 06:02:26 -0400 Received: from ozlabs.org ([203.10.76.45]:59974) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TLt7O-0003xG-Df for qemu-devel@nongnu.org; Wed, 10 Oct 2012 06:02:22 -0400 From: Rusty Russell In-Reply-To: <20121009210901.GY14867@jl-vm1.vm.bytemark.co.uk> References: <874nmajcmj.fsf@codemonkey.ws> <87y5jhpuu2.fsf@rustcorp.com.au> <87bogddq0l.fsf@codemonkey.ws> <5072EA14.30809@redhat.com> <87k3v1gfw1.fsf@codemonkey.ws> <507333F1.1060000@redhat.com> <874nm4u1in.fsf@codemonkey.ws> <87sj9o8qn7.fsf@rustcorp.com.au> <87sj9oh0pm.fsf@codemonkey.ws> <87haq48hds.fsf@rustcorp.com.au> <20121009210901.GY14867@jl-vm1.vm.bytemark.co.uk> Date: Wed, 10 Oct 2012 14:14:47 +1030 Message-ID: <87txu36le8.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: Re: [Qemu-devel] Using PCI config space to indicate config location List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jamie Lokier Cc: Anthony Liguori , kvm@vger.kernel.org, "Michael S. Tsirkin" , qemu-devel , virtualization@lists.linux-foundation.org, Gerd Hoffmann Jamie Lokier writes: > Rusty Russell wrote: >> I don't think it'll be that bad; reset clears the device to unknown, >> bar0 moves it from unknown->legacy mode, bar1/2/3 changes it from >> unknown->modern mode, and anything else is bad (I prefer being strict so >> we catch bad implementations from the beginning). > > Will that work, if the guest with kernel that uses modern mode, kexecs > to an older (but presumed reliable) kernel that only knows about legacy mode? > > I.e. will the replacement kernel, or (ideally) replacement driver on > the rare occasion that is needed on a running kernel, be able to reset > the device hard enough? Well, you need to reset the device, so yes. Cheers, Rusty.