Avi Kivity wrote: > On 06/15/2009 03:45 PM, Anthony Liguori wrote: >>>> This last option makes sense to me: in a real world the user has >>>> control over where he places the device on the bus, so why >>>> not with qemu? >>> >>> Yes, the user build the machine using the command line and monitor >>> (or, in 2017, the machine configuration file), >> >> >> Considering pbrook just posted a machine config for arm, I think it >> would be rather sad if pc wasn't converted to it by 2017... > > I'd be sad too, but not surprised. > >>> then turns on the power. Command line options are the parts lying >>> around when we start. >>> >>> btw, -drive needs to be separated: >>> >>> -controller type=lsi1234,pci_addr=foobar,name=blah >>> -drive file=foo.img,controller=blah,index=0 >>> -drive file=bar.img,controller=blah,index=1 >>> >>> Drives to not have pci addresses. >> >> Drivers don't have indexes and buses but we specify it on the -drive >> line. > > Drives do have indexes. On old parallel scsi drives you set the index > by clicking a button on the back of the drive to cycle through scsi > addresses 0-7. An IDE drive's index is determined by the cable > (master/slave). A SATA drive's index is determined by which header on > the motherboard the drive connects to. It's not at all that simple. SCSI has a hierarchical address mechanism with 0-7 targets but then potentially multiple LUNs per target. Today, we always emulate a single LUN per target but if we ever wanted to support more than 7 disks on a SCSI controller, we would have to add multiple LUN support too. So the current linear unit= parameter is actually pretty broken for SCSI. For IDE, it's a combination of bus, slot, and master/slave. For virtio, it's just a PCI address. What we really need is something that is more opaque and controller specific. For instance, if we were going to do controllers... -controller type=lsi1234,pci_addr=foobar,name=blah -controller-disk controller=blah,target=0,lun=1,name=sda -controller type=ide,pci_addr=barfoo,name=ide -controller-disk controller=ide,slot=secondary,cable=slave,name=hdd -drive file=foo.img,controller-disk=sda -drive file=bar.img,controller-disk=hdd And having "-hdd file=foo.img" be short-hand for "-drive file=%s,controller-disk=%s". > > > If by bus you mean the if= parameter, then drives certainly do have > buses. Just try connecting the scsi drive from the previous paragraph > to a USB port. No, I meant drive file=foo.img,bus=3. If that doesn't seem obvious what it should do to you that's because it isn't at all obvious :-) It ends up skipping a predefined number of locations in the drive table. This is pretty broken fundamentally because it assumes controllers always support a fixed number of devices. Nothing really respects bus_id though so in practice, I assume it's almost universally broken. Regards, Anthony Liguori _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
