Each virtio thread was reading/draining the pause_evt pipe when
detecting the associated event. Problem is, when a virtio device has
multiple threads, they all share the same pause_evt pipe, which can
prevent some threads from receiving the event. If the first thread to
catch the event is quickly clearing the pipe, some other threads might
simply miss the event and they will not enter the "paused" state as
expected.
This is a behavior that was spotted with virtio-net as it usually uses
2 threads by default (1 for TX/RX queues and 1 for the control queue).
The way to solve this issue is by letting each thread drain the pipe
during the resume codepath, that is after the thread has been unparked.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The same way the VM and the vCPUs are restored in a paused state, all
devices associated with the device manager must be restored in the same
paused state.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
When a virtio device is paused an event is written to the appropriate
"pause" EventFd for the device. This will be noticed by the the device's
epoll_wait(), an atomic bool checked an if true then the thread is
parked(). When resuming the bool is reset and the thread is unpark()ed.
However the event triggering the pause is still in the EventFd so the
epoll_wait() will continue to return but because the boolean is not set
the thread will not be park()ed but instead we will busy loop around an
event that is not being consumed.
The solution is to drain the "pause" EventFd when the event is first
received and thus the epoll_wait() will only return for the pause event
once. This resolves the infinite epoll_wait() wake-ups.
Fixes: #869
Signed-off-by: Rob Bradford <robert.bradford@intel.com>
Thanks to the recently introduced function notifier() in the
VirtioInterrupt trait, all vhost-user devices can now bypass
listening onto an intermediate event fd as they can provide the
actual fd responsible for triggering the interrupt directly to
the vhost-user backend.
In case the notifier does not provide the event fd, the code falls
back onto the creation of an intermediate event fd it needs to listen
to, so that it can trigger the interrupt on behalf of the backend.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Callbacks are not the most Rust idiomatic way of programming. The right
way is to use a Trait to provide multiple implementation of the same
interface.
Additionally, a Trait will allow for multiple functions to be defined
while using callbacks means that a new callback must be introduced for
each new function we want to add.
For these two reasons, the current commit modifies the existing
VirtioInterrupt callback into a Trait of the same name.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Due to the amount of code currently duplicated across vhost-user devices,
the stats for this commit is on the large side but it's mostly more
duplicated code, unfortunately.
Migratable and Snapshotable placeholder implementations are provided as
well, making all vhost-user devices Migratable.
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
New event is added in VhostUserEpollHandler for vhost-user fs,
but the total event count is not update accordingly. Fix the
issue and refactor the event data setting for new event
expansion in the future.
Signed-off-by: Cathy Zhang <cathy.zhang@intel.com>
In order to factorize the code between vhost-user-net and virtio-fs one
step further, this patch extends the vhost-user handler implementation
to support slave requests.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
vhost-user framwork could provide good performance in data intensive
scenario due to the memory sharing mechanism. Implement vhost-user-net
device to get the benefit for Rust-based VMMs network.
Signed-off-by: Cathy Zhang <cathy.zhang@intel.com>
