On Mon, Apr 20, 2015 at 08:33:18AM -0700, Stephen Hemminger wrote: > On Mon, 20 Apr 2015 15:59:06 +0200 > "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > > On Thu, Apr 16, 2015 at 02:21:10PM -0700, Stephen Hemminger wrote: > > > On Thu, 16 Apr 2015 09:43:24 +0200 > > > "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > > > > > > On Wed, Apr 15, 2015 at 09:59:34AM -0700, Stephen Hemminger wrote: > > > > > The driver already supported INTX interrupts but had no in kernel > > > > > function to enable and disable them. > > > > > > > > > > It is possible for userspace to do this by accessing PCI config > > > > > directly, but this racy > > > > > > > > How is it racy? We have userspace using this interface, > > > > if there's a race I want to fix it. > > > > > > There is nothing to prevent two threads in user space doing > > > read/modify write at the same time. > > > > Well that's a userspace bug then - so let's drop that > > from commit log lest people think this fixes some > > kernel bugs. read/modify/write to the same register > > is at least an easy to grasp problem, creating > > an extra interface for the same function opens up > > the possibility that some userspace will do > > read/modify/write from one thread with irqcontrol > > from another thread, creating more races. > > > > > The bigger issue is that DPDK needs to support multiple UIO > > > interface types. And with current model there is no abstraction. > > > The way to enable/disable IRQ is different depending on the UIO > > > drivers. > > > > OK compatibility with other devices might be useful, but what are the > > other UIO drivers DPDK supports? I only found support for igb_uio so > > far, and that doesn't seem to be upstream. > > > > Currently, supports: > igb_uio, uio_pci_generic (as well as vfio) > > There are additional drivers which been submitted but not accepted for Xen and HyperV > both of which require special uio drivers. Well vfio doesn't have irq_control, does it? So I'd say it's best to wait and see before we commit to a new ABI then. You probably need to support existing kernels anyway, if igb_uio makes it upstream, then adding an interface that's consistent with it will make sense. -- MST -- 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
