On Fri, May 26, 2017 at 04:28:52PM +0200, Maxime Coquelin wrote:
This series aims at specifying ans implementing the protocol update
required to support device IOTLB with user backends.
In this second non-RFC version, main changes are:
- spec fixes and clarification
- rings information update has been restored back to ring
enablement time
- Work around GCC 4.4.7 limitation wrt assignment in unnamed union at
declaration time.
The series can be tested with vhost_iotlb_proto_v2 branch on my gitlab
account[0].
The slave requests channel part is re-used from Marc-André's series
submitted
last year[1], with main changes from original version being
request/feature
names renaming and addition of the REPLY_ACK feature support.
Regarding IOTLB protocol, one noticeable change is the IOTLB miss
request
reply made optionnal (i.e. only if slave requests it by setting the
VHOST_USER_NEED_REPLY flag in the message header). This change provides
more flexibility in the backend implementation of the feature.
The protocol is very close to kernel backends, except that a new
communication channel is introduced to enable the slave to send
requests to the master.
[0]:https://gitlab.com/mcoquelin/dpdk-next-virtio/commits/vhost_iotlb_proto_v2
[1]:https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg00095.html
Overall, this looks good to me. I do think patch 3 isn't a good idea
though, if slave wants something let it request it.
Need to find out why does vhost in kernel want the used ring iotlb at
start time - especially considering we aren't even guaranteed one entry
covers the whole ring, and invalidates should affect all addresses at
least in theory.