From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754286AbbATLKP (ORCPT ); Tue, 20 Jan 2015 06:10:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44335 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754172AbbATLKM (ORCPT ); Tue, 20 Jan 2015 06:10:12 -0500 Date: Tue, 20 Jan 2015 13:09:55 +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: <20150120110955.GF26442@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150120104040.GJ31174@grmbl.mre> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > 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. > 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? > > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c > > index de03df9..26afb56 100644 > > --- a/drivers/char/virtio_console.c > > +++ b/drivers/char/virtio_console.c > > @@ -1986,6 +1986,12 @@ static int virtcons_probe(struct virtio_device *vdev) > > bool multiport; > > bool early = early_put_chars != NULL; > > > > + if (!vdev->config->get) { > > + dev_err(&vdev->dev, "%s failure: config access disabled\n", > > + __func__); > > + return -EINVAL; > > + } > > + > > > Amit