On Thursday 16 July 2009 20:31:01 Michael S. Tsirkin wrote: > On Wed, Jul 15, 2009 at 03:08:29PM -0700, Greg KH wrote: > > On Wed, Jul 15, 2009 at 11:13:40PM +0300, Michael S. Tsirkin wrote: > > > This adds a generic uio driver that can bind to any PCI device. First > > > user will be virtualization where a qemu userspace process needs to > > > give guest OS access to the device. > > > > > > Interrupts are handled using the Interrupt Disable bit in the PCI > > > command register and Interrupt Status bit in the PCI status register. > > > All devices compliant to PCI 2.3 (circa 2002) and all compliant PCI > > > Express devices should support these bits. Driver detects this > > > support, and won't bind to devices which do not support the Interrupt > > > Disable Bit in the command register. > > > > > > It's expected that more features of interest to virtualization will be > > > added to this driver in the future. Possibilities are: mmap for device > > > resources, MSI/MSI-X, eventfd (to interface with kvm), iommu. > > > > > > Acked-by: Chris Wright <chrisw@xxxxxxxxxx> > > > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > > > --- > > > > > > Hans, Greg, please review and consider for upstream. > > > > > > This is intended to solve the problem in virtualization that shared > > > interrupts do not work with assigned devices. Earlier versions of this > > > patch have circulated on kvm@vger. > > > > How does this play with the pci-stub driver that I thought was written > > to solve this very problem? > > AFAIK the problem pci stub was written to solve is simply to bind to a > device. You then have to use another kernel module which looks the > device up with something like pci_get_bus_and_slot to do anything > useful. In particular, for non-shared interrupts, we can disable the > interrupt in the apic. But this does not work well for shared > interrupts. Thus this work. > > The uio driver will be used in virtualization scenarious, a couple > of possible ones that have been mentioned on the kvm list are: > - device assignment (guest access to device) for simple devices with > shared interrupts: emulating PCI is tricky enough to better be done in > userspace. shared interrupt support is important as it happens > with real devices One comments for shared interrupt: if you means guest device shares interrupt with device in other domain(that means guest or host), it's still a security hole, and our position seems still won't-do it. Could you explain how the situation change with this patch? I am not sure if I understand your meaning completely... Thanks. -- regards Yang, Sheng > - simple communication between guest and host: > we create a virtual device in host, and userspace > driver in guest gets events and passes them on > to e.g. dbus. shared interrupt support is important > to avoid wasting irqs > > > Will it conflict? > > No in a sense that you can't bind both drivers to the same device. > > > In fact, it looks like you copied the comments for this driver directly > > from the pci-stub driver :) > > Right. > > > How about moving that documentation into a place that people will notice > > it, like the rest of the UIO documentation? > > OK. > > > And right now you are just sending the irq to userspace, what is > > userspace supposed to do with it? > > Userspace uses libpci (i.e. pci sysfs) to talk to the device and to > re-enable interrupts by writing to the command register. > > In the case of device assignment, this will be qemu which > acts as a proxy for driver running in guest context. > In case of uio loaded in guest, the driver will be in guest > userspace, and the device is emulated in qemu. > > > Do you have a userspace program that > > uses this interface today to verify that everything works? If so, care > > to provide a pointer to it? > > Sure. I used an emulated device for this. > First, you patch qemu to add the device: > http://www.linux-kvm.org/downloads/mst/test_irq.patch > > Now, run with the new kernel (-kernel flag), adding > -device test-irq > > Once in guest, assign the device id > echo "1af4 2009" > /sys/bus/pci/drivers/uio_pci_generic/new_id > > Compile and run this driver: > http://www.linux-kvm.org/downloads/mst/testuio.c > (it does not use any libraries besides libc, > so just gcc testuio.c -o testuio) > > And now make the device assert interrupts, like this: > > while > sleep 1 > do > setpci -s 00:04.0 0x40.B=0x1 > done > > You should see messages printed as the driver gets interrupts, but no > error messages about missed interrupts. > > > thanks, > > > > greg k-h > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
