On 02/07/2011 09:57 AM, Nicholas A. Bellinger wrote: > Greetings all, > > [Topic] > > A hybrid target fabric module for QEMU/KVM SCSI para-virtualization > > [Abstract] > > Currently we use the TCM_Loop v4 fabric module with mainline .38 target > code to present SCSI LUNs with high level multi-fabric (iSCSI, FC, SAS) > SPC-3 port WWN emulation into KVM guests using two different forms of > QEMU HBA hardware emulation. However both of these currently require > interaction with the QEMU block layer and extra overhead of OS > independent code running in user-space connected to our existing > SG_IO/BSG interfaces. This also has the limitiation that we currently > cannot perform explict SCSI Initiator Port access management for LUNs > also present via TCM_Loop SCSI LLD driver on the KVM host. > > Recently there has been an off-list discussion between myself and > members of the QEMU/KVM community, and they have expressed an interest > in seeing a native paravirtualized SCSI passthrough available to QEMU > guests with direct interaction into TCM fabric module code running on > KVM host. This would be using existing CDB level port emulation code in > target_core_fabric_lib.c, and (mostly) generic fabric control plane in > target_core_fabric_configfs.c.. Beyond the TCM fabric module specifics, > this will require: > > *) An asynchronous I/O capable virtio interface for KVM that does not > require direct QEMU block-layer interaction > > *) A multi-fabric WWN naming capable TCM fabric module using native > virtio-scsi connections to individual KVM guests for kernel-level > passthrough into TCM backend storage. (eg: similar to TCM_Loop, but w/o > the Linux/SCSI LLD frontend, and full explict Initiator port NodeACL + > MappedLUN control abstraction) > > *) Guest OS specific para-virtualized SCSI driver packages (similar to > virtio-blk) performing SCSI I/O handoff into passthrough interface via > SCSI I_T nexues, with proper T10 WWN Port and LUN naming provided from > underlying TCM v4.x infrastructure (eg: full compat w/ existing SPC-3 > capable cluster clients) > I agree with the 2 above points on a better scsi-based Kernel-only passthrough code in the KVM host. But the 3rd point, could we not used any one of the few LLDs that already exist? I think there are already 3 of these, no? including the one Microsoft submitted. > --nab > Thanks Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
