Re: [libvirt] [PATCH 1/2] Add VSCSI bus type and VSCSI controller type for pseries guest.

On Fri, May 04, 2012 at 05:49:54PM +0800, Li Zhang wrote: > On 05/04/2012 05:04 PM, Daniel P. Berrange wrote: >> On Fri, May 04, 2012 at 10:05:13AM +0800, Li Zhang wrote: >>> Now, there is only SCSI bus and controller type in libvirt. >>> And when configuring VSCSI controller, it needs to configure >>> the spapr-vio bus address type externally. It's a little >>> inconvenient to configure the controller type. >>> >>> This patch is to add VSCSI bus type and VSCSI controller type. >>> And handle with the problems when VSCSI and SCSI devices >>> working together, by assign the even number to index of >>> VSCSI controller and odd number to index of SCSI controller. >>> >>> And when the VSCSI controller is always assigned as SPAPRVIO >>> bus address type and SCSI controller will be always assigned >>> as PCI bus address, which is implemented according to the >>> controllers' type. >>> >>> So when one disk is based on VSCSI controller, then assign >>> the bus as 'vscsi', and one right VSCSI controller will be >>> selected. >> >> I'm not at all convinced by this description that we need >> a new controller type. At most we need a separate<address/> >> type for the VSCSI controller under an existing SCSI controller >> element. >> > > The problem is that when using two kinds of SCSI controller, > vscsi and scsi, which are based on different address type and > model at the same time, it needs to specify the model and address > type externally. And it's hard to find the right controller for > disk to use, only by the 'sdx'. Sure, but there's nothing special about s390 / vSCSI in that respect. If you have a guest with a SATA controller and a SCSI controller you have the same problem. If you have multiple disk controllers assigned to the guest, and are adding a disk, then you are responsible for providing an<address> element for the disk to indicate which controller it should be added to.

The automagic guessing of controllers is only ever intended to work in the simple case where you have 1 kind of controller

Daniel