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Wed, 6 May 2020 16:53:08 +0000 (UTC) Date: Wed, 6 May 2020 17:53:05 +0100 From: "Dr. David Alan Gilbert" To: Cornelia Huck Subject: Re: [PATCH v16 QEMU 08/16] vfio: Register SaveVMHandlers for VFIO device Message-ID: <20200506165305.GP2743@work-vm> References: <1585084154-29461-1-git-send-email-kwankhede@nvidia.com> <1585084154-29461-9-git-send-email-kwankhede@nvidia.com> <20200325150248.6661e1bd@w520.home> <20200504223726.5d4bb9ce@x1.home> <20200506063846.GB19334@joy-OptiPlex-7040> <20200506115856.012c88d8.cohuck@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200506115856.012c88d8.cohuck@redhat.com> User-Agent: Mutt/1.13.4 (2020-02-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.61; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/06 05:50:09 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001, T_HK_NAME_DR=0.01, URIBL_BLOCKED=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: "Tian, Kevin" , "Liu, Yi L" , "cjia@nvidia.com" , "eskultet@redhat.com" , "Yang, Ziye" , "qemu-devel@nongnu.org" , "Zhengxiao.zx@Alibaba-inc.com" , "shuangtai.tst@alibaba-inc.com" , Kirti Wankhede , "Wang, Zhi A" , "mlevitsk@redhat.com" , "pasic@linux.ibm.com" , "aik@ozlabs.ru" , Alex Williamson , "eauger@redhat.com" , "felipe@nutanix.com" , "jonathan.davies@nutanix.com" , Yan Zhao , "Liu, Changpeng" , "Ken.Xue@amd.com" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Cornelia Huck (cohuck@redhat.com) wrote: > On Wed, 6 May 2020 02:38:46 -0400 > Yan Zhao wrote: >=20 > > On Tue, May 05, 2020 at 12:37:26PM +0800, Alex Williamson wrote: > > > It's been a long time, but that doesn't seem like what I was asking. > > > The sysfs version checking is used to select a target that is likely = to > > > succeed, but the migration stream is still generated by a user and th= e > > > vendor driver is still ultimately responsible for validating that > > > stream. I would hope that a vendor migration stream therefore starts > > > with information similar to that found in the sysfs interface, allowi= ng > > > the receiving vendor driver to validate the source device and vendor > > > software version, such that we can fail an incoming migration that th= e > > > vendor driver deems incompatible. Ideally the vendor driver might al= so > > > include consistency and sequence checking throughout the stream to > > > prevent a malicious user from exploiting the internal operation of th= e > > > vendor driver. Thanks, >=20 > Some kind of somewhat standardized marker for driver/version seems like > a good idea. Further checking is also a good idea, but I think the > details of that need to be left to the individual drivers. Standardised markers like that would be useful; although the rules of how to compare them might be a bit vendor specific; but still - it would be good for us to be able to dump something out when it all goes wrong. > > > =20 > > maybe we can add a rw field migration_version in > > struct vfio_device_migration_info besides sysfs interface ? > >=20 > > when reading it in src, it gets the same string as that from sysfs; > > when writing it in target, it returns success or not to check > > compatibility and fails the migration early in setup phase. >=20 > Getting both populated from the same source seems like a good idea. >=20 > Not sure if a string is the best value to put into a migration stream; > maybe the sysfs interface can derive a human-readable string from a > more compact value to be put into the migration region (and ultimately > the stream)? Might be overengineering, just thinking out aloud here. A string might be OK fi you specify a little about it. Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK