On 08.07.2013, at 22:08, Anthony Liguori wrote: > Peter Maydell <peter.maydell@xxxxxxxxxx> writes: > >> On 8 July 2013 14:45, Alexander Graf <agraf@xxxxxxx> wrote: >>> On 08.07.2013, at 15:23, Peter Maydell wrote: >>>> Now I'm completely confused. Why would assigned devices >>>> have anything to do with this? Can you explain in more >>>> detail, because I don't really see what you're suggesting? >>> >>> The only missing link we have to create any device using -device >>> on the command line is the IRQ line enumeration. If we can allocate >>> IRQ lines automatically, we can put any command line given -device >>> onto our main system bus that is non-pci, non-isa. >> >> If the user is expected to be able to get the MMIO address >> right (which they'd have to specify on the command line >> somehow too) why not require them to specify the IRQ number >> while they're doing it? I'm a bit suspicious of anything >> that requires the user to specify to that level of detail >> though, since it requires a lot of inside knowledge about the >> board. >> >> This is the whole reason for having the separate transport: >> the board gets to take care of the board specific detail of >> how to wire up the transport, and the user just asks to >> create the backends that plug automatically into it. >> The virtio command line options are complicated and confusing >> enough as it is. >> >>> So if we want to ever support VFIO for platform devices, >>> the user will want to pass -device vfio-ahci,foo=bar on >>> the command line to assign an AHCI device. >> >> This appears to be seriously short on actually specifying >> enough information to wire a device up. >> >>> The only infrastructure blocker we have for that today >>> is the IRQ allocation. >> >> DMA lines? Specifying the right location in the address space? >> >>> Maybe we could even try to be as smart as putting the MMIO >>> regions into guest address space intelligently automatically. >> >> This sounds likely to cause problems with migration unless >> we can guarantee that we always pick the same place. > > I think we're trying to fit a square peg into a round hole. > > virtio-mmio is a virtio transport where each device has a dedicated set > of system resources. > > Alex, it sounds like you want virtio-mmio-bus which would be a single > set of system resources that implemented a virtio bus on top of it. Well, what I really want is a sysbus that behaves like PCI from a usability point of view ;). Alex _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
