On Thu, Apr 29, 2010 at 12:29:40PM -0700, Tom Lyon wrote: > Michael, et al - sorry for the delay, but I've been digesting the comments > and researching new approaches. > > I think the plan for V4 will be to take things entirely out of the UIO > framework, and instead have a driver which supports user mode use of > "well-behaved" PCI devices. I would like to use read and write to support > access to memory regions, IO regions, or PCI config space. Config space is a > bitch because not everything is safe to read or write, but I've come up with > a table driven approach which can be run-time extended for non-compliant > devices (under root control) which could then enable non-privileged users. > For instance, OHCI 1394 devices use a dword in config space which is not > formatted as a PCI capability, root can use sysfs to enable access: > echo <offset> <readbits> <writebits> > > /sys/dev/pci/devices/xxxx:xx:xx.x/<yyy>/config_permit > > > A "well-behaved" PCI device must have memory BARs >= 4K for mmaping, must > have separate memory space for MSI-X that does not need mmaping > by the user driver, must support the PCI 2.3 interrupt masking, and must not > go totally crazy with PCI config space (tg3 is real ugly, e1000 is fine).
e1000 has a good driver in kernel, though. > > Again, my primary usage model is for direct user-level access to network > devices, not for virtualization, but I think both will work. I suspect that without mmap and (to a lesser extent) write-combining, this would be pretty useless for virtualization. > So, I will go outside UIO because: > 1 - it doesn't allow reads and writes to sub-drivers, just irqcontrol > 2 - it doesn't have ioctls > 3 - it has its own interrupt model which doesn't use eventfds > 4 - it's ugly doing the new stuff and maintaining backwards compat. > > I hereby solicit comments on the name and location for the new driver. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
