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Tue, 9 Jun 2020 14:02:45 +0000 (GMT) Received: from oc3016276355.ibm.com (unknown [9.145.16.61]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 9 Jun 2020 14:02:45 +0000 (GMT) Subject: Re: [PATCH v2 1/1] virtio-ccw: auto-manage VIRTIO_F_IOMMU_PLATFORM if PV To: Halil Pasic , Cornelia Huck References: <20200514221155.32079-1-pasic@linux.ibm.com> <20200520121507-mutt-send-email-mst@kernel.org> <20200606013217.2cffa3ed.pasic@linux.ibm.com> <20200608181428.3c6f127c.cohuck@redhat.com> <20200608190045.319dd68b.pasic@linux.ibm.com> <20200609084402.35d317ec.cohuck@redhat.com> <20200609114130.0ca9190b.pasic@linux.ibm.com> From: Pierre Morel Message-ID: <1d914b70-e30c-ea1f-3356-2fc53b63ce58@linux.ibm.com> Date: Tue, 9 Jun 2020 16:02:45 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200609114130.0ca9190b.pasic@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216, 18.0.687 definitions=2020-06-09_06:2020-06-09, 2020-06-09 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 lowpriorityscore=0 spamscore=0 impostorscore=0 priorityscore=1501 malwarescore=0 adultscore=0 mlxscore=0 cotscore=-2147483648 phishscore=0 mlxlogscore=999 bulkscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006090107 Received-SPF: pass client-ip=148.163.156.1; envelope-from=pmorel@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/09 10:03:48 X-ACL-Warn: Detected OS = Linux 3.x [generic] [fuzzy] X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, KHOP_DYNAMIC=0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Thomas Huth , Boris Fiuczynski , Janosch Frank , David Hildenbrand , Claudio Imbrenda , Richard Henderson , "Michael S. Tsirkin" , qemu-devel@nongnu.org, Christian Borntraeger , qemu-s390x@nongnu.org, Viktor Mihajlovski , David Gibson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020-06-09 11:41, Halil Pasic wrote: > On Tue, 9 Jun 2020 08:44:02 +0200 > Cornelia Huck wrote: > >> On Mon, 8 Jun 2020 19:00:45 +0200 >> Halil Pasic wrote: >> >> ...snip... >> >> I mean, can a virtio devices without IOMMU_PLATFORM act as a transition >> blocker (i.e. an attempt by a guest to move to pv would fail?) >> > > I don't know. Janosch could answer that, but he is on vacation. Adding > Claudio maybe he can answer. My understanding is, that while it might be > possible, it is ugly at best. The ability to do a transition is > indicated by a CPU model feature. Indicating the feature to the guest and > then failing the transition sounds wrong to me. The guest image is encrypted and the transition to PV is done by the stage 3 boot loader, part of the loaded image, before Linux is started. At this moment the guest is not aware of the virtio devices. Regards, Pierre -- Pierre Morel IBM Lab Boeblingen