Re: [KVM PATCH v4 3/3] kvm: add iosignalfd support

From: Avi Kivity
Date: Sun May 31 2009 - 05:12:00 EST

Gregory Haskins wrote:
This is closer to how the original series worked, but Avi asked for a
data-match token and thus the cookie was born. I think the rationale is
that we can't predict whether the same eventfd will be registered more
than once, and thus we need a way to further qualify it. However, to
your point, I cannot think of a valid use case for having the same fd
registered to the same address more than once, so perhaps your fd/addr
tuple is sufficient and we can drop the cookie (or, really, rename it to
"trigger" ;)


This is just how virtio works. To kick ring N of device X, it writes N to a port specific to X.

If we lose N, then we don't know which ring was kicked and have to check them all.

May we can rename cookie to data_match to make it explicit. If the data doesn't match, the eventfd isn't kicked.

(Mark, same as we have arbitrary ring->MSI mappings (allowing one MSI to notify multiple rings), perhaps we should have the same capability for the other direction? So the guest could kick mulitple rings with one write, or just one ring, according to personal preference.

error compiling committee.c: too many arguments to function

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