On Wed, Oct 30, 2013 at 08:30:22AM -0600, Alex Williamson wrote: > On Wed, 2013-10-30 at 12:40 +0200, Gleb Natapov wrote: > > On Tue, Oct 29, 2013 at 10:13:22AM -0600, Alex Williamson wrote: > > > The KVM device interface allocates a struct kvm_device and calls > > > kvm_device_ops.create on it from KVM VM ioctl KVM_CREATE_DEVICE. > > > This returns a file descriptor to the user for them to set/get/check > > > further attributes. On closing the file descriptor, one would assume > > > that kvm_device_ops.destroy is called and all traces of the device > > > would go away. One would be wrong, it actually does nothing more > > > than release the struct kvm reference, waiting until the VM is > > > destroyed before doing more. This leaves devices that only want a > > > single instance of themselves per VM in a tough spot. > > > > > This is by design. Otherwise locking will be needed on each device access > > and for interrupt controllers this is unnecessary serialization and > > overhead. Device API is not designed for devices that can go away while > > machine is running anyway, so after creation device is only destroyed > > during VM destruction. > > Hmm, ok. In that case I can drop this patch and I think the rest just > boils down to userspace use of the device. I had been close()'ing the > kvm device fd when all QEMU vfio devices are detached, but I can just as > easily leave it open in case a new device is added later. I'll send out > a new series after doing some more review and testing. Do you have any > comments on the rest of the series? Thanks, > If I understand 4/4 correctly if there is VFIO device connected we assume non coherent domain. How hard it would be to do proper checking in this path series? -- Gleb. -- 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
