Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754360AbaK0KzM (ORCPT ); Thu, 27 Nov 2014 05:55:12 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60319 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753329AbaK0KzK (ORCPT ); Thu, 27 Nov 2014 05:55:10 -0500 Date: Thu, 27 Nov 2014 12:54:34 +0200 From: "Michael S. Tsirkin" To: Cornelia Huck Cc: linux-kernel@vger.kernel.org, David Miller , rusty@au1.ibm.com, nab@linux-iscsi.org, pbonzini@redhat.com, Rusty Russell , Christian Borntraeger , linux390@de.ibm.com, Martin Schwidefsky , Heiko Carstens , Pawel Moll , Ohad Ben-Cohen , Sudeep Dutt , Ashutosh Dixit , Greg Kroah-Hartman , Nikhil Rao , Siva Yerramreddy , lguest@lists.ozlabs.org, linux-s390@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v4 04/42] virtio: disable virtio 1.0 in transports Message-ID: <20141127105434.GA10037@redhat.com> References: <1416933600-21398-1-git-send-email-mst@redhat.com> <1416933600-21398-5-git-send-email-mst@redhat.com> <20141125182942.3890fe7b.cornelia.huck@de.ibm.com> <20141125212011.GA22343@redhat.com> <20141126100954.3811e594.cornelia.huck@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141126100954.3811e594.cornelia.huck@de.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 26, 2014 at 10:09:54AM +0100, Cornelia Huck wrote: > On Tue, 25 Nov 2014 23:20:11 +0200 > "Michael S. Tsirkin" wrote: > > > On Tue, Nov 25, 2014 at 06:29:42PM +0100, Cornelia Huck wrote: > > > On Tue, 25 Nov 2014 18:41:35 +0200 > > > "Michael S. Tsirkin" wrote: > > > > > > > disable virtio 1.0 in transports that don't > > > > support it yet. > > > > > > I'd prefer if you disabled it for _every_ transport in this patch, > > > until the needed infrastructure is in place. Else this is a bit > > > confusing. > > > > Well the only transports left are pci and rpoc, and these only > > read the low 32 bit of the features from the device - > > so there's nothing to clear. > > > > E.g. the following would be even more confusing, would it not: > > > > u32 features; > > .... > > features &= ~BIT_ULL(VIRTIO_F_VERSION_1); > > > > Agree? > > Maybe you should tweak the patch description a bit and mention that you > only disable virtio 1.0 for transports where it is actually needed? > > (...) Yes, I did that now. > > > FWIW, as negotiating a revision >= 1 is a pre-req for virtio 1.0 > > > support on ccw, virtio 1.0 is already implicitly disabled. > > > > Ah, you mean device guarantees that VIRTIO_F_VERSION_1 isn't set > > if guest sets revision to 0? > > Yes, the bit will not be offered if the revision is 0 or has not been > set at all. > > > In that case it's probably best to drop this from both ccw > > devices. > > There's only one ccw transport :) > > The old s390 virtio transport in kvm_virtio.c is not part of virtio 1.0. It might or might not be a good idea to add code in kvm_virtio.c blacklisting VIRTIO_F_VERSION_1, just in case there's a buggy device that sets it. As correct devices won't set it, I don't think we need to worry about it too much. We can make it a patch on top later if we want. -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/