From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754885Ab2IFKCx (ORCPT ); Thu, 6 Sep 2012 06:02:53 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:50663 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752908Ab2IFKCw (ORCPT ); Thu, 6 Sep 2012 06:02:52 -0400 Date: Thu, 6 Sep 2012 03:02:48 -0700 From: Kent Overstreet To: "Michael S. Tsirkin" Cc: Rusty Russell , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] virtio-blk: Fix kconfig option Message-ID: <20120906100247.GA27355@koverstreet-glaptop> References: <20120903044133.GA9980@moria.home.lan> <87wr0ae26e.fsf@rustcorp.com.au> <20120906074113.GA5902@koverstreet-glaptop> <20120906084403.GD17656@redhat.com> <20120906092512.GB5902@koverstreet-glaptop> <20120906094956.GB22816@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120906094956.GB22816@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 06, 2012 at 12:49:56PM +0300, Michael S. Tsirkin wrote: > On Thu, Sep 06, 2012 at 02:25:12AM -0700, Kent Overstreet wrote: > > On Thu, Sep 06, 2012 at 11:44:03AM +0300, Michael S. Tsirkin wrote: > > > On Thu, Sep 06, 2012 at 12:41:13AM -0700, Kent Overstreet wrote: > > > > On Tue, Sep 04, 2012 at 03:53:53PM +0930, Rusty Russell wrote: > > > > > Kent Overstreet writes: > > > > > > > > > > > CONFIG_VIRTIO isn't exposed, everything else is supposed to select it > > > > > > instead. > > > > > > > > > > This is a slight mis-understanding. It's supposed to be selected by > > > > > the particular driver, probably virtio_pci in your case. > > > > > > > > So are you saying virtio-blk depends on virtio-pci? If so, the kconfig > > > > should have that. > > > > > > > > As is, VIRTIO_BLK just has: > > > > depends on EXPERIMENTAL && VIRTIO > > > > > > > > which is flat out broken. > > > > > > I don't think anything is broken. > > > Can you show an example of a broken configuration? > > > > Do you not understand the difference between depends an selects? > > Or did you not read my original mail? > > Flip off everything in drivers -> virtio > > > > Now go to drivers -> block and try to turn on virtio-blk. > > > > It's not listed! > > Yes. Because you disabled all virtio backends. > It does not make sense to have any frontends. How's a user - or even another kernel developer who isn't familiar with virtio - supposed to know that? I still don't know what exactly a virtio backend is - the term isn't even mentioned anywhere that I've seen. Whatever it is though virtio-blk should be depending on _that_, not a config option that _isn't exposed in the menu_! > > Now go back to drivers -> virtio and turn on (randomly) balloon. > > > > Go back to drivers -> block, and now you can turn on virtio-blk! > > > > Do you see what's wrong with this picture? > > Yes. You got unlucky with your random guess. > It's a bug in balloon kconfig: it should not > select virtio. > I sent a patch to fix that yesterday. Then it's also a bug in the comments at the top of drivers/virtio/Kconfig. And besides that, how the _hell_ is a user supposed to know to turn on VIRTIO_PCI before VIRTIO_BLK? It's not documented anywhere (if that is what's supposed to happen! I still don't know) and even if it was documented, having one kconfig option depend on something that's exposed in a _completely different menu_ is just made of fail.