This implements synchronized time-travel mode which - using a special
application on a unix socket - lets multiple machines take part in a
time-travelling simulation together.
The protocol for the unix domain socket is defined in the new file
include/uapi/linux/um_timetravel.h.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Implement in-band notifications that are necessary for running
vhost-user devices under externally synchronized time-travel
mode (which is in a follow-up patch). This feature makes what
usually should be eventfd notifications in-band messages.
We'll prefer this feature, under the assumption that only a
few (simulation) devices will ever support it, since it's not
very efficient.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This driver *can* be a module, but then its parameters (socket path)
are untrusted data from inside the VM, and that isn't allowed. Allow
the code to only be built-in to avoid that.
Fixes: 5d38f32499 ("um: drivers: Add virtio vhost-user driver")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Anton Ivanov <anton.ivanov@cambridgegreys.co.uk>
Signed-off-by: Richard Weinberger <richard@nod.at>
When we get an interrupt from the socket getting readable,
and start reading, there's a possibility for a race. This
depends on the implementation of the device, but e.g. with
qemu's libvhost-user, we can see:
device virtio_uml
---------------------------------------
write header
get interrupt
read header
read body -> returns -EAGAIN
write body
The -EAGAIN return is because the socket is non-blocking,
and then this leads us to abandon this message.
In fact, we've already read the header, so when the get
another signal/interrupt for the body, we again read it
as though it's a new message header, and also abandon it
for the same reason (wrong size etc.)
This essentially breaks things, and if that message was
one that required a response, it leads to a deadlock as
the device is waiting for the response but we'll never
reply.
Fix this by spinning on -EAGAIN as well when we read the
message body. We need to handle -EAGAIN as "no message"
while reading the header, since we share an interrupt.
Note that this situation is highly unlikely to occur in
normal usage, since there will be very few messages and
only in the startup phase. With the inband call feature
this does tend to happen (eventually) though.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
If the connection drops, just remove the device, we don't try
to recover from this right now.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Implement the VHOST_USER_PROTOCOL_F_REPLY_ACK extension for both
slave requests (previous patch) where we have to reply and our
own requests where it helps understand if the slave failed.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Implement the communication channel for the device to notify
us of some events, and notably implement the handling of the
config updates needed for the combination of this feature
and VHOST_USER_PROTOCOL_F_CONFIG.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This module allows virtio devices to be used over a vhost-user socket.
Signed-off-by: Erel Geron <erelx.geron@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Johannes Berg