From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-s390-owner@vger.kernel.org>
Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:35929 "EHLO
        us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org
        with ESMTP id S1728815AbgFPNvK (ORCPT
        <rfc822;linux-s390@vger.kernel.org>); Tue, 16 Jun 2020 09:51:10 -0400
Date: Tue, 16 Jun 2020 15:50:51 +0200
From: Cornelia Huck <cohuck@redhat.com>
Subject: Re: [PATCH v2 1/1] s390: virtio: let arch accept devices without
 IOMMU feature
Message-ID: <20200616155051.5b842895.cohuck@redhat.com>
In-Reply-To: <e130c5e7-40e5-40a8-eac3-c2d17c90ee7b@linux.ibm.com>
References: <1592224764-1258-1-git-send-email-pmorel@linux.ibm.com>
        <1592224764-1258-2-git-send-email-pmorel@linux.ibm.com>
        <20200616115202.0285aa08.pasic@linux.ibm.com>
        <ef235cc9-9d4b-1247-c01a-9dd1c63f437c@linux.ibm.com>
        <20200616135726.04fa8314.pasic@linux.ibm.com>
        <20200616141744.61b3a139.cohuck@redhat.com>
        <e130c5e7-40e5-40a8-eac3-c2d17c90ee7b@linux.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-s390-owner@vger.kernel.org
List-ID: <linux-s390.vger.kernel.org>
To: Pierre Morel <pmorel@linux.ibm.com>
Cc: Halil Pasic <pasic@linux.ibm.com>, linux-kernel@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, mst@redhat.com, jasowang@redhat.com, kvm@vger.kernel.org, linux-s390@vger.kernel.org, virtualization@lists.linux-foundation.org, thomas.lendacky@amd.com, David Gibson <david@gibson.dropbear.id.au>, Ram Pai <linuxram@us.ibm.com>, Heiko Carstens <heiko.carstens@de.ibm.com>, Vasily Gorbik <gor@linux.ibm.com>

On Tue, 16 Jun 2020 15:41:20 +0200
Pierre Morel <pmorel@linux.ibm.com> wrote:

> On 2020-06-16 14:17, Cornelia Huck wrote:
> > On Tue, 16 Jun 2020 13:57:26 +0200
> > Halil Pasic <pasic@linux.ibm.com> wrote:
> >   
> >> On Tue, 16 Jun 2020 12:52:50 +0200
> >> Pierre Morel <pmorel@linux.ibm.com> wrote:
> >>  
> >>>>>    int virtio_finalize_features(struct virtio_device *dev)
> >>>>>    {
> >>>>>    	int ret = dev->config->finalize_features(dev);
> >>>>> @@ -179,6 +184,10 @@ int virtio_finalize_features(struct virtio_device *dev)
> >>>>>    	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
> >>>>>    		return 0;
> >>>>>    
> >>>>> +	if (arch_needs_iommu_platform(dev) &&
> >>>>> +		!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM))
> >>>>> +		return -EIO;
> >>>>> +  
> >>>>
> >>>> Why EIO?  
> >>>
> >>> Because I/O can not occur correctly?
> >>> I am open to suggestions.  
> >>
> >> We use -ENODEV if feature when the device rejects the features we
> >> tried to negotiate (see virtio_finalize_features()) and -EINVAL when
> >> the F_VERSION_1 and the virtio-ccw revision ain't coherent (in
> >> virtio_ccw_finalize_features()). Any of those seems more fitting
> >> that EIO to me. BTW does the error code itself matter in any way,
> >> or is it just OK vs some error?  
> > 
> > If I haven't lost my way, we end up in the driver core probe failure
> > handling; we probably should do -ENODEV if we just want probing to fail
> > and -EINVAL or -EIO if we want the code to moan.
> >   
> 
> what about returning -ENODEV and add a dedicated warning here?
> 

Sounds good at least to me.