[Qemu-devel] Re: UIO interrupts being lost

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jun 24, 2010 at 05:43:15PM -0600, Cam Macdonell wrote:
> Hi Michael,
> 
> I'm trying to write a uio driver for my shared memory device for KVM
> and I'm running into a situation where several interrupts in quick
> succession are not all triggering the callback function in my kernel
> UIO driver, say 2 out of 5.  My driver does not set the Interrupt
> Disable bit and if it helps, I'm using MSI-X interrupts.  Even without
> the interrupt disable bit set, is there still a window where
> successive interrupts can be lost if they arrive too quickly?
> 
> Thanks,
> Cam

Yes, I think so: if an interrupt is delivered when
ISR is running, it gets queued, but a second one
gets lost.

A queueing mechanism is necessary to avoid losing
information, e.g. virtio implements exactly that.
Why don't you reuse virtio for signalling?

If I understand what Anthony said correctly,
he objected to the specific implementation,
not to the idea of reusing virtio spec and code.

-- 
MST