The local variable used to read the ports won't be valid after we return from
the function. Moving it to be an instance member is not ideal, but it work if
we don't unmask the ports until we're ready signaling them all.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
If there is some error opening the xenstore - for instance, if we run
without privileges, we should bail out or we will segfault later.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
This is not required for OSv, but is required for userspace operation.
It won't work without it.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
After the latest reactor rework from Nadav, it is no longer allowed to use eventfds
in the reactor for OSv. Change the code to use the reactor notifier instead.
We could just use that instead of semaphores altogether. But because the semaphore is
per listener, we need a translation anyway. So let's keep this one doing the interrupt
processing, and the semaphores doing the rest of the work.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
This is useful for features that are provided incrementally, so may not
be present on all hypervisors. If the value is not present, return a
user-provided default, which also has a system-provided default (0).
We current have one port per event channel. We need to have a list of
semaphores that will all be made ready when an interrupt kicks in. This is
useful in the case where both tx and rx are bound to the same event channel.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
If we do that, plus make it an instance method, we should be able to use
make_ready_port. This is consistent with the userspace implementation and
from that point any changes there will be propagated to both.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
The representation of an event channel as an integer poses a problem, in which
waiting on an integer port doesn't work well when the same event channel is
assigned for both tx and rx. The future will be ready for one of the sides, but
we won't process the other.
One alternative is to have conditions in the future processing, and in case the
event channels are bound to the same port, process both events. But a better
solution is to use a class to represent the bound ports, and instances of those
classes will have their own pending methods.
Infrastructure will be written in a following patch to make sure that all
listeners to the same port will be made ready when an interrupt kicks in
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Instead of returning a reference to a grant that is already present in an
array, defer the initialization. This is how the OSv driver handles it, and I
honestly am not sure if this is really needed: it seems to me we should be able
to just reuse the old grants. I need to check in the backend code if we can be
any smarter than this.
However, right now we need to do something to recycle the buffers, and just
re-doing the refs would lead to inconsistencies. So the best by now is to close
and reopen the grants, and then later on rework this in a way that works for
both the initial setup and the recycle.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Enhance gntref with some useful operations. Also provide a default object that
represents an invalid grant.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
The Xen code registers a function that calls semaphore::signal as
an interrupt handler, however that function is not smp safe and may crash,
and in events it generates are likely to be ignored, since they are just
appended to the reactor queue without any real wakeup to the reactor thread.
Switch to using an eventfd. That's still unsafe, but a little better, since
its signalling is smp safe, and will cause the reactor thread to wake up
in case it was asleep.
With this, we are able to receive multiple packets.
We used gnttab_grant_foreign_access() instead of
gnttab_grant_foreign_access_ref(). While the two functions have similar
enough signatures, they do very different things.
With the change, we are able to receive packets from Xen, though we crash
immediately.
We used gnttab_grant_foreign_access() instead of
gnttab_grant_foreign_access_ref(). While the two functions have similar
enough signatures, they do very different things.
With the change, we are able to transmit packets through Xen.
This patch enables xen event channels. It creates the placeholder for the
kernel evtchns when we move to OSv as well.
The main problem with this patch, is that evtchn::pending can return more than
one evtchn, so this that I am doing here is technically wrong. We should probably
call keep_doing() in pending() itself, and have that to store the references to
futures equivalent to the possible event channels, that would then be made ready.
I am, however, having a bit of a hard time coding this, since it's still
unclear how, once the future is consumed, we would generate the next.
Please note: All of this is moot if we disable "split event channels", which
can be done by masking that feature in case it is even available. In that case,
only one event channel will be notified, and when ready, we process both tx and
rx. This is yet another reason why I haven't insisted so much in fixing this properly
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
This patch creates a seastar enabled version of the xen gntalloc device.
TODO: grow the table dynamically, and fix the index selection algorithm. Shouldn't
just always bump 1.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
This patch enables to interact with xenstore. Since now OSv now fakes the
presence of libxenstore, the code is the same for userspace and kernel.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
