From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:27524 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726261AbgFPNle (ORCPT ); Tue, 16 Jun 2020 09:41:34 -0400 Subject: Re: [PATCH v2 1/1] s390: virtio: let arch accept devices without IOMMU feature 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> <20200616135726.04fa8314.pasic@linux.ibm.com> <20200616141744.61b3a139.cohuck@redhat.com> From: Pierre Morel Message-ID: Date: Tue, 16 Jun 2020 15:41:20 +0200 MIME-Version: 1.0 In-Reply-To: <20200616141744.61b3a139.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Cornelia Huck , Halil Pasic Cc: 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 , Ram Pai , Heiko Carstens , Vasily Gorbik On 2020-06-16 14:17, Cornelia Huck wrote: > On Tue, 16 Jun 2020 13:57:26 +0200 > Halil Pasic wrote: > >> On Tue, 16 Jun 2020 12:52:50 +0200 >> Pierre Morel 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? -- Pierre Morel IBM Lab Boeblingen