diff options
| -rw-r--r-- | docs/specs/index.rst | 1 | ||||
| -rw-r--r-- | docs/specs/ivshmem-spec.rst (renamed from docs/specs/ivshmem-spec.txt) | 63 | ||||
| -rw-r--r-- | docs/specs/pci-ids.rst | 2 | ||||
| -rw-r--r-- | docs/system/devices/ivshmem.rst | 2 |
4 files changed, 26 insertions, 42 deletions
diff --git a/docs/specs/index.rst b/docs/specs/index.rst index 30a0cf3d47..e60c837754 100644 --- a/docs/specs/index.rst +++ b/docs/specs/index.rst @@ -26,3 +26,4 @@ guest hardware that is specific to QEMU. fw_cfg vmw_pvscsi-spec edu + ivshmem-spec diff --git a/docs/specs/ivshmem-spec.txt b/docs/specs/ivshmem-spec.rst index 1beb3a01ec..2d8e80055b 100644 --- a/docs/specs/ivshmem-spec.txt +++ b/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 diff --git a/docs/specs/pci-ids.rst b/docs/specs/pci-ids.rst index d6707fa069..c0a3dec2e7 100644 --- a/docs/specs/pci-ids.rst +++ b/docs/specs/pci-ids.rst @@ -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. diff --git a/docs/system/devices/ivshmem.rst b/docs/system/devices/ivshmem.rst index e7aaf34c20..ce71e25663 100644 --- a/docs/system/devices/ivshmem.rst +++ b/docs/system/devices/ivshmem.rst @@ -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 ~~~~~~~~~~~~~~~~~~~~~~ |