Re: [libvirt-users] Questions regarding hostdev scsi

Hi! I'm oVirt developer responsible for most of 'hostdev' support. While working on SCSI passthrough (that is hostdev type='scsi'), I've encountered few issues I'm not sure how to solve somewhat effectively and nicely. Just a note - oVirt by default disables 'dynamic_ownership', meaning we have to handle endpoint ownership/labeling ourselves. This is not something I can change in a short term. Also, oVirt uses libvirt's python API, I'll do my best using the original C names. To report and construct the hostdev element, I am using virConnectListAllNodeDevices. To get information about the devices, virNodeDeviceGetXMLDesc is called on each device. For PCI and USB devices, XML of the device contains everything needed to a) construct the element, b) fix endpoint permissions. SCSI device becomes more difficult as the information is scattered between multiple devices. Devices I have encountered contain this subtree: <device> <name>scsi_host4</name> <path>/sys/devices/pci0000:00/0000:00:1f.2/ata5/host4</path> <parent>pci_0000_00_1f_2</parent> <capability type='scsi_host'> <host>4</host> <unique_id>5</unique_id> </capability> </device> <device> <name>scsi_target4_0_0</name> <path>/sys/devices/pci0000:00/0000:00:1f.2/ata5/host4/target4:0:0</path> <parent>scsi_host4</parent> <capability type='scsi_target'> <target>target4:0:0</target> </capability> </device> <device> <name>scsi_4_0_0_0</name> <path>/sys/devices/pci0000:00/0000:00:1f.2/ata5/host4/target4:0:0/4:0:0:0</path> <parent>scsi_target4_0_0</parent> <driver> <name>sd</name> </driver> <capability type='scsi'> <host>4</host> <bus>0</bus> <target>0</target> <lun>0</lun> <type>disk</type> </capability> </device> <device> <name>block_sdb_Samsung_SSD_850_PRO_256GB_S251NXAGB42213R</name> <path>/sys/devices/pci0000:00/0000:00:1f.2/ata5/host4/target4:0:0/4:0:0:0/block/sdb</path> <parent>scsi_4_0_0_0</parent> <capability type='storage'> <block>/dev/sdb</block> <bus>ata</bus> <drive_type>disk</drive_type> <model>Samsung SSD 850</model> <vendor>ATA</vendor> <serial>Samsung_SSD_850_PRO_256GB_S251NXAGB42213R</serial> <size>256060514304</size> <logical_block_size>512</logical_block_size> <num_blocks>500118192</num_blocks> </capability> </device> <device> <name>scsi_generic_sg1</name> <path>/sys/devices/pci0000:00/0000:00:1f.2/ata5/host4/target4:0:0/4:0:0:0/scsi_generic/sg1</path> <parent>scsi_4_0_0_0</parent> <capability type='scsi_generic'> <char>/dev/sg1</char> </capability> </device> To construct the element, information from device scsi_4_0_0_0 is needed for <address> element (minus the host element). Adapter element is one of the places that I am not sure which information I can rely on, currently 'host' element from scsi_4_0_0_0 is used to form string 'scsi_host{host}'. Is this correct? Reliable? Whole different issue is locating the endpoint (/dev/sg{int}) to set the permissions. From the subtree, it's apparent that it is included in device called scsi_generic_sg1, but there is no *direct* link between scsi_4_0_0_0 and scsi_generic_sg1. At this point, we present user with devices matching capability='scsi', therefore to get the information 2 additional parses of the tree would have to be done. Other way would be reporting 'scsi_generic' capability, where only 2 additional virNodeDeviceLookupByName calls would be required (to descend 2 levels). Is there anything *really* wrong with this approach? Are there any other options without dynamic ownershit? Seclabel doesn't seem to be available. I'm thankful for any hints.

Regards, mpolednik _______________________________________________ libvirt-users mailing list libvirt-users(a)redhat.com https://www.redhat.com/mailman/listinfo/libvirt-users