From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754309AbbAUGo3 (ORCPT ); Wed, 21 Jan 2015 01:44:29 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50210 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754142AbbAUGo2 (ORCPT ); Wed, 21 Jan 2015 01:44:28 -0500 Date: Wed, 21 Jan 2015 08:44:09 +0200 From: "Michael S. Tsirkin" To: Amit Shah Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Rusty Russell , cornelia.huck@de.ibm.com, Arnd Bergmann , Greg Kroah-Hartman Subject: Re: [PATCH v3 04/16] virtio/console: verify device has config space Message-ID: <20150121064409.GA13320@redhat.com> References: <1421256142-11512-1-git-send-email-mst@redhat.com> <1421256142-11512-5-git-send-email-mst@redhat.com> <20150120104040.GJ31174@grmbl.mre> <20150120110955.GF26442@redhat.com> <20150121061452.GV31174@grmbl.mre> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150121061452.GV31174@grmbl.mre> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 21, 2015 at 11:44:52AM +0530, Amit Shah wrote: > On (Tue) 20 Jan 2015 [13:09:55], Michael S. Tsirkin wrote: > > On Tue, Jan 20, 2015 at 04:10:40PM +0530, Amit Shah wrote: > > > On (Wed) 14 Jan 2015 [19:27:35], Michael S. Tsirkin wrote: > > > > Some devices might not implement config space access > > > > (e.g. remoteproc used not to - before 3.9). > > > > virtio/console needs config space access so make it > > > > fail gracefully if not there. > > > > > > Do we know any such devices? Wondering what prompted this patch. If > > > it's just theoretical, I'd rather let it be like this, and pull this > > > in when there's a device that doesn't have config space. > > > > Yes, with virtio 1.0 config space can be in a separate BAR now. If > > that's not enabled by BIOS (e.g. out of space), we won't have config > > space. > > I'm still not sure whether we should pull in this patch before > actually seeing a failure. > > You do have a dev_err which tells why the probe failed, so it's an > acceptable compromise I suppose. > > > > Also, just the console functionality (i.e. F_MULTIPORT is unset) is > > > available w/o config space access. > > > > Supporting this by gracefully disabling F_MULTIPORT > > would require getting this info from driver before > > features are finalized. > > Alternatively, check F_MULTIPORT and only fail if set? > > Let me know, I'll cook up a patch. > > Yes, failing only if F_MULTIPORT is set is a better option (if we have > to fail). OK, that's easy I think - will send a patch on top. > > > In fact, getting this patch in > > > would mean remoteproc wouldn't even run in its pre-config days... > > > > It seems to have get callback unconditionally now - or did I miss > > something? > > What I meant was remoteproc doesn't depend on the config space, only > uses the console functionality. If remoteproc devices didn't expose a > config space, this patch would cause it to lose its console > functionality for no apparent reason. > > > Amit Better than crashing on jump to NULL? -- MST