Michael S. Tsirkin wrote:
On Mon, May 04, 2009 at 12:21:28PM +0300, Avi Kivity wrote:
Michael S. Tsirkin wrote:
So what I see is transports providing something like:
struct virtio_interrupt_mapping {
int virtqueue;
int interrupt;
};
map_vqs_to_interrupt(dev, struct virtio_interrupt_mapping *, int nvirtqueues);
unmap_vqs(dev);
Isn't that the same thing? Please explain the flow.
So to map vq 0 to vector 0, vq 1 to vector 1 and vq 2 to vector 2 the driver would do:
struct virtio_interrupt_mapping mapping[3] = { {0, 0}, {1, 1}, {2, 2} };
vec = map_vqs_to_interrupt(dev, mapping, 3);
if (vec) {
error handling
}
and then find_vq as usual.
Yes, that works.
Given that pci_enable_msix() can fail, we can put the retry loop in
virtio-pci, and instead of a static mapping, supply a dynamic mapping:
static void get_vq_interrupt(..., int nr_interrupts, int vq)
{
/* reserve interrupt 0 to config changes; round-robin vqs to
interrupts */
return 1 + (vq % (nr_interrupts - 1));
}
driver_init()
{
map_vqs_to_interrupt(dev, get_vq_interrupt);
}
map_vqs_to_interrupts() would call get_vq_interrupt() for each vq,
assuming the maximum nr_interrupts, and retry with smaller nr_interrupts
on failure.
Since guest drivers are going to do round-robin most of the time, I
think the right thing to do is to make the API simple, along the lines
proposed by Rusty, and make the guest/host ABI rich enough to support
arbitrary mapping, along the lines proposed by you. We can always change
the API, ABI is harder.
We can provide the round-robin mapper as a helper, so driver code
doesn't need to implement any callback if they're satisfied with the
default.
--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.
--
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
