https://github.com/arm-software/revere-demo

Example program demonstrating the use of the Revere-AMU System Architecture from userspace, with VFIO
https://github.com/arm-software/revere-demo

accelerator revere-amu vfio vfio-pci

Last synced: 12 months ago
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Example program demonstrating the use of the Revere-AMU System Architecture from userspace, with VFIO

Host: GitHub
URL: https://github.com/arm-software/revere-demo
Owner: ARM-software
License: bsd-3-clause
Created: 2019-07-19T11:29:56.000Z (almost 7 years ago)
Default Branch: master
Last Pushed: 2020-09-15T10:12:12.000Z (almost 6 years ago)
Last Synced: 2025-06-14T21:08:39.493Z (about 1 year ago)
Topics: accelerator, revere-amu, vfio, vfio-pci
Language: C
Homepage: https://developer.arm.com/architectures/system-architectures/accelerators
Size: 42 KB
Stars: 5
Watchers: 3
Forks: 8
Open Issues: 0
Metadata Files:
- Readme: README.md
- License: LICENSE

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README

Revere VFIO demo
================

Principles
----------

The Revere VFIO demo is a standalone example using a Revere device, originally
from userspace through VFIO.
It establishes a connection with a hardware inversion "accelerator". Data is
exchanged with the accelerator through Revere messages.
Alternatively, the demo can also run in loopback mode, where the data is looped
back directly, bypassing the accelerator.

License
-------

This code is licensed under the open source BSD, clause 3 license. See LICENSE
for more information.

Build
-----

To build:

```
$ ./autogen.sh
$ ./configure
$ make
```

Run
---

When using VFIO, run the demo as root to avoid permissions issues.

To run:

```
# modprobe vfio_iommu_type1 allow_unsafe_interrupts=1
# modprobe vfio-pci ids=13b5:ff81
# revere-vfio-demo --vfio-group /dev/vfio/2 --device 0000:00:03.0
```

Note: you need to adapt the vfio group and device to those corresponding to the
Revere PF on your platform.

Running with VFIO in loop back mode is done with:

```
# revere-vfio-demo --vfio-group /dev/vfio/2 --device 0000:00:03.0 --loopback
```

Command line options allow to change various other parameters of the demo, such
as the total number of packets or the packet size. See all supported command
line options in the online help with:

```
$ revere-vfio-demo -h
```

Details
-------

Details of the files for this demo:

```
+-- autogen.sh
+-- cmdline.c
+-- cmdline.h
+-- configure.ac
+-- LICENSE
+-- main.c ............. Demo top level
+-- platform.c ......... Platform abstraction layer
+-- platform.h
+-- Makefile.am
+-- README
+-- regs.h ............. Registers access functions
+-- revere_dev.c ....... Function for Revere setup
+-- revere_dev.h
+-- revere.h ........... Revere-AMU generated header
+-- revere_hw.h ........ A few Revere registers aliases
+-- vfio.c ............. VFIO functions
`-- vfio.h
```

The demo goes through the following steps:

1. Allocate memory for all i/o buffers, which are shared with the Revere device.
2. With VFIO, open the device and map memory into Revere IOVA space. Also, map
BAR0 into our process address space.
Also, turn on BME.
3. Setup the Revere device: setup Revere management interface, then using the
management interface, setup the AMI-HWs in the accelerator, an AMI-SW and
connect them with sessions.
4. Exchange data with the inversion agent and verify that it has been inverted.
5. Teardown everything and exit.

Here is the Revere setup configured by the demo (omitting the management
interface):

```
Rings in memory
+-----------------------+
.---------------. | Inversion accelerator |
| +-+-+-+-+-+ | | (AHA 0) |
`->| | | | | |--' | |
+-+-+-+-+-+ AMI-SW 0 | AMI-HW 0 |
| +-----------+ ASN 0 +-----------+ |
`........>| TX AMS 0 @---------->@ RX AMS 0 |--. |
| | | | | |
| | | | Invert |
| | | | | |
..........| RX AMS 0 @<----------@ TX AMS 0 |<-' |
V +-----------+ ASN 1 +-----------+ |
+-+-+-+-+-+ | |
.->| | | | | |--. +-----------------------+
| +-+-+-+-+-+ |
`---------------'
```

Command line options allow to select different AMI-HWs in the accelerator for Tx
and Rx, and change the AHA ID.

In dma mode, the sw selects a different accelerator (called the DMA agent, AHA 3).
It receives a revere message with this format:

```
struct DMAPacket {
uint64_t of_buf_stash_ctl;
uint64_t src;
uint64_t dst;
uint32_t len;
uint32_t rsvd0;
uint32_t invert;
}
```

and copies len bytes from src to dst buffers, inverted if invert == 1.
Finally the DMA agent sends a response message back to notify of the DMA completion.

In loopback mode a single session is setup. No AMI-HW is setup and the inversion
accelerator is bypassed. The data is received "as is" without inversion:

```
Rings in memory

.---------------.
| +-+-+-+-+-+ |
`->| | | | | |--'
+-+-+-+-+-+ AMI-SW 0
| +-----------+
`........>| TX AMS 0 @-----------.
| | |
| | | ASN 0
| | |
..........| RX AMS 0 @<----------'
V +-----------+
+-+-+-+-+-+
.->| | | | | |--.
| +-+-+-+-+-+ |
`---------------'
```

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