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doc: edit ivshmem hld doc

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Signed-off-by: David B. Kinder <david.b.kinder@intel.com>
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David B. Kinder 2020-06-05 15:48:06 -07:00 committed by David Kinder
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doc/developer-guides/hld/ivshmem-hld.rst
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ACRN Shared Memory Based Inter-VM Communication ACRN Shared Memory Based Inter-VM Communication
############################################### ###############################################
To support inter virtual machines communication based on shared memory ACRN supports inter-virtual machine communication based on a shared
mechanism, ACRN device model/hypervisor emulate a virtual PCI device memory mechanism, The ACRN device model and hypervisor emulate a virtual
(Called ``ivshmem`` device) to expose the base address and size of shared PCI device (called an ``ivshmem`` device) to expose the base address and
memory. size of this shared memory.
Inter-VM Communication Overview Inter-VM Communication Overview
******************************* *******************************
@ -17,28 +17,33 @@ Inter-VM Communication Overview
ACRN shared memory based inter-vm communication architecture ACRN shared memory based inter-vm communication architecture
Two solutions of ivshmem device: dm-land and hypervisor-land. For dm-land, The ``ivshmem`` device is emulated in the ACRN device model (dm-land)
the ivshmem device emulated in acrn device model and its shared memory region and its shared memory region is allocated from the Service VM's memory
is allocated from the Service VM's memory space. For hypervisor-land, it is space. This solution only supports communication between post-launched
emulated in hypervisor and the shared memory regions are reserved in hypervisor's VMs.
memory space. The former solution only supports interactive between post-launched
VMs and the latter one can work for both pre-launched and post-launched VMs. The
hypervisor-land solution is WIP, plan to support in the near future.
- Ivshmem dm – The ivshmem device model implements register virtualization .. note:: In a future implementation, the ``ivshmem`` device could
instead be emulated in the hypervisor (hypervisor-land) and the shared
memory regions reserved in the hypervisor's memory space. This solution
would work for both pre-launched and post-launched VMs.
ivshmem dm:
The ivshmem device model implements register virtualization
and shared memory mapping. Will support notification/interrupt mechanism and shared memory mapping. Will support notification/interrupt mechanism
in future. in future.
- Ivshmem server – A daemon for inter-VM notification capability, ivshmem server:
currently, it has not been implemented, so the inter-VM communication A daemon for inter-VM notification capability,
doesn’t support notification mechanism. This is currently not implemented, so the inter-VM communication
doesn't support a notification mechanism.
Ivshmem Device Introduction Ivshmem Device Introduction
*************************** ***************************
The ivshmem device is a virtual standard PCI device, it consists of two The ``ivshmem`` device is a virtual standard PCI device consisting of
BARs(BAR0 and BAR2), one is used for emulate interrupt related registers, two Base Address Registers (BARs): BAR0 is used for emulating interrupt related registers,
another one is used for exposing shared memory region. The ivshmem device and BAR2 is used for exposing shared memory region. The ``ivshmem`` device
doesn't support any extra capabilities. doesn't support any extra capabilities.
Configuration Space Definition Configuration Space Definition
@ -58,36 +63,51 @@ Configuration Space Definition
MMIO Registers Definition MMIO Registers Definition
+---------------------------+----------+-------+-----------------------------------------------------------------------------------------------------------------------+ .. list-table::
| Register | Offset | RW | Description | :widths: auto
+===========================+==========+=======+=======================================================================================================================+ :header-rows: 1
| IVSHMEM\_IRQ\_MASK\_REG | 0x0 | R/W | Interrupt Status register is used for legacy interrupt. |
| | | | | * - Register
| | | | Currently, the ivshmem doesn’t support interrupt, so this is reserved. | - Offset
+---------------------------+----------+-------+-----------------------------------------------------------------------------------------------------------------------+ - Read/Write
| IVSHMEM\_IRQ\_STA\_REG | 0x4 | R/W | Interrupt Mask register is used for legacy interrupt. | - Description
| | | | | * - IVSHMEM\_IRQ\_MASK\_REG
| | | | Currently, the ivshmem doesn’t support interrupt, so this is reserved. | - 0x0
+---------------------------+----------+-------+-----------------------------------------------------------------------------------------------------------------------+ - R/W
| IVSHMEM\_IV\_POS\_REG | 0x8 | RO | Inter VM Position register is used to identify VM ID, currently its value is zero. | - Interrupt Status register is used for legacy interrupt.
+---------------------------+----------+-------+-----------------------------------------------------------------------------------------------------------------------+ ivshmem doesn't support interrupts, so this is reserved.
| IVSHMEM\_DOORBELL\_REG | 0xc | WO | Doorbell register is used to trigger an interrupt to the peer VM. Currently, the ivshmem doesn’t support interrupt. | * - IVSHMEM\_IRQ\_STA\_REG
+---------------------------+----------+-------+-----------------------------------------------------------------------------------------------------------------------+ - 0x4
- R/W
- Interrupt Mask register is used for legacy interrupt.
ivshmem doesn't support interrupts, so this is reserved.
* - IVSHMEM\_IV\_POS\_REG
- 0x8
- RO
- Inter-VM Position register is used to identify the VM ID.
Currently its value is zero.
* - IVSHMEM\_DOORBELL\_REG
- 0xC
- WO
- Doorbell register is used to trigger an interrupt to the peer VM.
ivshmem doesn't support interrupts.
Usage Usage
***** *****
To support two post-launched VMs communication via ivshmem device, user To support two post-launched VMs communicating via an ``ivshmem`` device,
needs to add below line as acrn-dm boot parameter. add this line as an acrn-dm boot parameter::
***-s slot, ivshmem, shm\_name,shm\_size*** -s slot, ivshmem, shm_name, shm_size
- -s slot – Specify the virtual PCI slot number where
- ivshmem – Virtual PCI device name - ``-s slot`` - Specify the virtual PCI slot number
- shm\_name – Specify a shared memory name, post-launched VMs with the - ``ivshmem`` - Virtual PCI device name
same *shm\_name* share a shared memory region.
- shm\_size – Specify a shared memory size, two communicating VMs need - ``shm_name`` - Specify a shared memory name. Post-launched VMs with the
to define the same size. same ``shm_name`` share a shared memory region.
- ``shm_size`` - Specify a shared memory size. The two communicating
VMs must define the same size.