tree 02e212c8eeeb52e74876408bb5e7e5d2febae379
parent cd9ae5fe47dfb9820976c3c38c70f4b07a5a1c36
author Michael S. Tsirkin <mst@redhat.com> 1396291838 +0300
committer Marcelo Tosatti <mtosatti@redhat.com> 1397754102 -0300

KVM: support any-length wildcard ioeventfd

It is sometimes benefitial to ignore IO size, and only match on address.
In hindsight this would have been a better default than matching length
when KVM_IOEVENTFD_FLAG_DATAMATCH is not set, In particular, this kind
of access can be optimized on VMX: there no need to do page lookups.
This can currently be done with many ioeventfds but in a suboptimal way.

However we can't change kernel/userspace ABI without risk of breaking
some applications.
Use len = 0 to mean "ignore length for matching" in a more optimal way.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>