docs/specs/ivshmem-spec.rst

2 Device Specification for Inter-VM shared memory device
7 and the host.  In order for all guests to be able to pick up the
17 For information on configuring the ivshmem device on the QEMU
41 - If you additionally need the capability for peers to interrupt each
44   configured for interrupts, obviously.
47 configured for interrupts.  It becomes safely accessible only after
49 revision 0 rather than 1.  Guest software should wait for the
54 it is configured for interrupts.
89 IVPosition Register: if the device is not configured for interrupts,
92 Before QEMU 2.6.0, the register may read -1 for a short while after
95 There is no good way for software to find out whether the device is
96 configured for interrupts.  A positive IVPosition means interrupts,
103 If the device is not configured for interrupts, the write is ignored.
114 The peer's interrupt for this vector then becomes pending.  There is
115 no way for software to clear the pending bit, and a polling mode of
130 When configured for interrupts, the peers share eventfd objects in
139 For each new client that connects to the server, the server
142 - creates eventfd file descriptors for the interrupt vectors,
143 - sends the ID and the file descriptor for the shared memory to the
145 - sends connect notifications for the new client to the other clients
146   (these contain file descriptors for sending interrupts),
147 - sends connect notifications for the other clients to the new client,
150   descriptors for receiving interrupts).
159 If the server terminates without sending disconnect notifications for
163 no way for the clients to connect to a restarted server.  The device
171 for debugging.
176 An ivshmem device configured for interrupts connects to an ivshmem
194    provides only 16 bits for them.
196 3. The number -1, accompanied by the file descriptor for the shared
199 4. Connect notifications for existing other clients, if any.  This is
202    descriptor.  These are for interrupting the peer with that ID using
203    vector 0,..,N-1, in order.  If the client is configured for fewer
205    for more, the extra vectors remain unconnected.
209    for receiving interrupts from peers using vector 0,..,N-1, in
210    order.  If the client is configured for fewer vectors, it closes
211    the extra file descriptors.  If it is configured for more, the
221   - Else, it's a disconnection notification for the peer with that ID.
233 An ivshmem device configured for interrupts receives eventfd file
234 descriptors for interrupting peers and getting interrupted by peers