@@ -26,3 +26,4 @@ guest hardware that is specific to QEMU.
fw_cfg
vmw_pvscsi-spec
edu
+ ivshmem-spec
similarity index 88%
rename from docs/specs/ivshmem-spec.txt
rename to docs/specs/ivshmem-spec.rst
@@ -1,4 +1,6 @@
-= Device Specification for Inter-VM shared memory device =
+======================================================
+Device Specification for Inter-VM shared memory device
+======================================================
The Inter-VM shared memory device (ivshmem) is designed to share a
memory region between multiple QEMU processes running different guests
@@ -12,42 +14,17 @@ can obtain one from an ivshmem server.
In the latter case, the device can additionally interrupt its peers, and
get interrupted by its peers.
+For information on configuring the ivshmem device on the QEMU
+command line, see :doc:`../system/devices/ivshmem`.
-== Configuring the ivshmem PCI device ==
-
-There are two basic configurations:
-
-- Just shared memory:
-
- -device ivshmem-plain,memdev=HMB,...
-
- This uses host memory backend HMB. It should have option "share"
- set.
-
-- Shared memory plus interrupts:
-
- -device ivshmem-doorbell,chardev=CHR,vectors=N,...
-
- An ivshmem server must already be running on the host. The device
- connects to the server's UNIX domain socket via character device
- CHR.
-
- Each peer gets assigned a unique ID by the server. IDs must be
- between 0 and 65535.
-
- Interrupts are message-signaled (MSI-X). vectors=N configures the
- number of vectors to use.
-
-For more details on ivshmem device properties, see the QEMU Emulator
-user documentation.
-
-
-== The ivshmem PCI device's guest interface ==
+The ivshmem PCI device's guest interface
+========================================
The device has vendor ID 1af4, device ID 1110, revision 1. Before
QEMU 2.6.0, it had revision 0.
-=== PCI BARs ===
+PCI BARs
+--------
The ivshmem PCI device has two or three BARs:
@@ -59,8 +36,7 @@ There are two ways to use this device:
- If you only need the shared memory part, BAR2 suffices. This way,
you have access to the shared memory in the guest and can use it as
- you see fit. Memnic, for example, uses ivshmem this way from guest
- user space (see http://dpdk.org/browse/memnic).
+ you see fit.
- If you additionally need the capability for peers to interrupt each
other, you need BAR0 and BAR1. You will most likely want to write a
@@ -77,10 +53,13 @@ accessing BAR2.
Revision 0 of the device is not capable to tell guest software whether
it is configured for interrupts.
-=== PCI device registers ===
+PCI device registers
+--------------------
BAR 0 contains the following registers:
+::
+
Offset Size Access On reset Function
0 4 read/write 0 Interrupt Mask
bit 0: peer interrupt (rev 0)
@@ -145,18 +124,20 @@ With multiple MSI-X vectors, different vectors can be used to indicate
different events have occurred. The semantics of interrupt vectors
are left to the application.
-
-== Interrupt infrastructure ==
+Interrupt infrastructure
+========================
When configured for interrupts, the peers share eventfd objects in
addition to shared memory. The shared resources are managed by an
ivshmem server.
-=== The ivshmem server ===
+The ivshmem server
+------------------
The server listens on a UNIX domain socket.
For each new client that connects to the server, the server
+
- picks an ID,
- creates eventfd file descriptors for the interrupt vectors,
- sends the ID and the file descriptor for the shared memory to the
@@ -189,7 +170,8 @@ vectors.
A standalone client is in contrib/ivshmem-client/. It can be useful
for debugging.
-=== The ivshmem Client-Server Protocol ===
+The ivshmem Client-Server Protocol
+----------------------------------
An ivshmem device configured for interrupts connects to an ivshmem
server. This section details the protocol between the two.
@@ -245,7 +227,8 @@ Known bugs:
* The protocol is poorly designed.
-=== The ivshmem Client-Client Protocol ===
+The ivshmem Client-Client Protocol
+----------------------------------
An ivshmem device configured for interrupts receives eventfd file
descriptors for interrupting peers and getting interrupted by peers
@@ -50,7 +50,7 @@ maintained as part of the virtio specification.
by QEMU.
1af4:1110
- ivshmem device (shared memory, ``docs/specs/ivshmem-spec.txt``)
+ ivshmem device (:doc:`ivshmem-spec`)
All other device IDs are reserved.
@@ -33,7 +33,7 @@ syntax when using the shared memory server is:
When using the server, the guest will be assigned a VM ID (>=0) that
allows guests using the same server to communicate via interrupts.
Guests can read their VM ID from a device register (see
-ivshmem-spec.txt).
+:doc:`../../specs/ivshmem-spec`).
Migration with ivshmem
~~~~~~~~~~~~~~~~~~~~~~