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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 3 Jan 2019 17:28:51 -0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x03HSoNi32243870 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 3 Jan 2019 17:28:50 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 92A8111C04A; Thu, 3 Jan 2019 17:28:50 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5C89711C052; Thu, 3 Jan 2019 17:28:50 +0000 (GMT) Received: from oc2783563651 (unknown [9.152.224.202]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 3 Jan 2019 17:28:50 +0000 (GMT) Date: Thu, 3 Jan 2019 18:28:49 +0100 From: Halil Pasic To: Cornelia Huck Cc: "Michael S . Tsirkin" , Jason Wang , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, virtio-dev@lists.oasis-open.org, Wei Wang Subject: Re: [PATCH 2/2] virtio: document virtio_config_ops restrictions In-Reply-To: <20190103160804.21438-3-cohuck@redhat.com> References: <20190103160804.21438-1-cohuck@redhat.com> <20190103160804.21438-3-cohuck@redhat.com> Organization: IBM X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19010317-0028-0000-0000-00000333555A X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19010317-0029-0000-0000-000023F055CD Message-Id: <20190103182849.7b0b0f0b@oc2783563651> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-01-03_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901030154 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 3 Jan 2019 17:08:04 +0100 Cornelia Huck wrote: > Some transports (e.g. virtio-ccw) implement virtio operations that > seem to be a simple read/write as something more involved that > cannot be done from an atomic context. > > Give at least a hint about that. > > Signed-off-by: Cornelia Huck > --- > include/linux/virtio_config.h | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h > index 7087ef946ba7..987b6491b946 100644 > --- a/include/linux/virtio_config.h > +++ b/include/linux/virtio_config.h > @@ -12,6 +12,11 @@ struct irq_affinity; > > /** > * virtio_config_ops - operations for configuring a virtio device > + * Note: Do not assume that a transport implements all of the operations > + * getting/setting a value as a simple read/write! Generally speaking, > + * any of @get/@set, @get_status/@set_status, or @get_features/ > + * @finalize_features are NOT safe to be called from an atomic > + * context. I think the only exception is @bus_name (and maybe @generation, I don't know) because it does not have to 'speak' with the hypervisor. If a transport operation has to 'speak' with the hypervisor, we do it by making it interpret a channel program. That means not safe to be called form atomic context. Or am I missing something? Regards, Halil > * @get: read the value of a configuration field > * vdev: the virtio_device > * offset: the offset of the configuration field