Am 10.07.2019 um 12:09 hat Paolo Bonzini geschrieben: > On 09/07/19 22:38, Dmitry Fomichev wrote: > > Currently, attaching zoned block devices (i.e. storage devices > > compliant to ZAC/ZBC standards) using several virtio methods doesn't > > work - the zoned devices appear as regular block devices at the guest. > > This may cause unexpected i/o errors and, potentially, some data > > corruption. > > > > To be more precise, attaching a zoned device via virtio-pci-blk, > > virtio-scsi-pci/scsi-disk or virtio-scsi-pci/scsi-hd demonstrates the > > above behavior. A simple fix is needed to make > > virtio-scsi-pci/scsi-block work and this is covered by a different > > patch. The virtio-scsi-pci/scsi-generic method appears to handle zoned > > devices without problems. > > The problem with this approach is that other devices (e.g. ide-hd or sd > card) also break with zoned devices and the only way to fix it would be > to add code denying zoned block devices to all of them. > > The question then becomes how to define a whitelist. One possiblity is > to add a QOM interface (for example TYPE_ZONED_BLOCK_SUPPORT) to > scsi-block and scsi-generic. In do_parse_drive you can query the > BlockBackend with bdrv_get_zoned_info, and return an error if the > backend is a zoned block device and the device does not implement > TYPE_ZONED_BLOCK_SUPPORT. (Commit 6b1566c is an example of adding a new > QOM interface; in your case, it would be simpler as the interface would > not have any method). Kevin, what do you think?
What about non-device users such as block jobs or (NBD) exports? Won't they have to special-case such devices, too? In fact, what about image format drivers or even filters? I feel that this needs to be managed at the BDS level somehow. Not sure which mechanism to use, though. Permissions would be suitable for a blacklist approach, but I agree with you that we need a whitelist instead. Hm... Actually, file-posix implements .bdrv_check_perm and could just refuse attaching a parent there if it doesn't request a specific permission like BLK_PERM_SUPPORT_ZONED. That should give us the whitelist semantics through existing infrastructure. Kevin