CV-Bowen opened a new pull request, #18265:
URL: https://github.com/apache/nuttx/pull/18265
## Summary
This PR adds a new API `virtio_read_config_bytes()` and updates VirtIO
drivers to use size-matched operations when reading the VirtIO configuration
space, following the VirtIO specification requirements.
### Why is this change needed?
According to the VirtIO specification:
> For the device-specific configuration space, the driver MUST use 8-bit
wide accesses for 8-bit wide fields, 16-bit wide and aligned accesses for
16-bit wide fields and 32-bit wide and aligned accesses for 32 and 64-bit wide
fields.
The current implementation uses `virtio_read_config()` to read strings (like
CPU names, MAC addresses, and tags) as a whole block, which violates the
specification. For string fields in the VirtIO config space, we should use
byte-by-byte read operations.
### What does this PR do?
1. **Add `virtio_read_config_bytes()` API**
(`include/nuttx/virtio/virtio-config.h`)
- New inline function that reads config space byte-by-byte
- Suitable for reading string-type fields that require 8-bit accesses
2. **Update `rpmsg_virtio` driver** (`drivers/rpmsg/rpmsg_virtio.c`)
- Use `virtio_read_config_bytes()` to read `host_cpuname` and
`remote_cpuname` strings
3. **Update `virtio-net` driver** (`drivers/virtio/virtio-net.c`)
- Use `virtio_read_config_bytes()` to read MAC address (6 bytes)
4. **Update `virtio-snd` driver** (`drivers/virtio/virtio-snd.c`)
- Use `virtio_read_config_member()` to read individual config members
(`jacks`, `streams`, `chmaps`)
- Each member is read with proper size-matched access
5. **Update `virtio_9p` driver** (`fs/v9fs/virtio_9p.c`)
- Use `virtio_read_config_bytes()` to read the tag string
## Impact
- **Stability**: Improves compatibility with VirtIO backends that strictly
enforce the specification
- **Compatibility**: No breaking changes; existing functionality preserved
- **Code Quality**: Better adherence to VirtIO specification
## Testing
### Build Verification
```bash
cmake -B cmake_out/v8a_netnsh -DBOARD_CONFIG=qemu-armv8a:netnsh -GNinja
cmake --build cmake_out/v8a_netnsh
cmake -B cmake_out/v8a_server -DBOARD_CONFIG=qemu-armv8a:rpserver -GNinja
cmake --build cmake_out/v8a_server
cmake -B cmake_out/v8a_proxy -DBOARD_CONFIG=qemu-armv8a:rpproxy -GNinja
cmake --build cmake_out/v8a_proxy
```
### Test Environment
- **Host OS**: Ubuntu 22.04
- **QEMU Version**: 9.2.3
- **Target**: qemu-armv8a
### Test Results
#### VirtIO Network/9p Test
```c
❯ /data/software/qemu/qemu-9.2.3/build/qemu-system-aarch64 -cpu cortex-a53
-nographic \
-machine virt,virtualization=on,gic-version=3 \
-chardev stdio,id=con,mux=on -serial chardev:con \
-global virtio-mmio.force-legacy=false \
-device virtio-serial-device,bus=virtio-mmio-bus.0 \
-chardev
socket,telnet=on,host=127.0.0.1,port=3450,server=on,wait=off,id=foo \
-device virtconsole,chardev=foo \
-device virtio-rng-device,bus=virtio-mmio-bus.1 \
-netdev
user,id=u1,hostfwd=tcp:127.0.0.1:10023-10.0.2.15:23,hostfwd=tcp:127.0.0.1:15001-10.0.2.15:5001
\
-device virtio-net-device,netdev=u1,bus=virtio-mmio-bus.2 \
-drive file=./mydisk-1gb.img,if=none,format=raw,id=hd \
-device virtio-blk-device,bus=virtio-mmio-bus.3,drive=hd \
-fsdev
local,security_model=none,id=fsdev0,path=/data/project/code/apache/nuttx \
-device virtio-9p-device,id=fs0,fsdev=fsdev0,mount_tag=host \
-mon chardev=con,mode=readline -kernel
./nuttx/cmake_out/v8a_netnsh/nuttx \
-gdb tcp::7777
[ 0.350000] pci_scan_bus: pci_scan_bus for bus 0
[ 0.350000] pci_scan_bus: class = 00000600, hdr_type = 00000000
[ 0.350000] pci_scan_bus: 00:00 [1b36:0008]
[ 0.350000] pci_setup_device: pbar0 set bad mask
[ 0.350000] pci_setup_device: pbar1 set bad mask
[ 0.350000] pci_setup_device: pbar2 set bad mask
[ 0.350000] pci_setup_device: pbar3 set bad mask
[ 0.360000] pci_setup_device: pbar4 set bad mask
[ 0.360000] pci_setup_device: pbar5 set bad mask
telnetd [4:100]
NuttShell (NSH) NuttX-12.10.0
nsh>
nsh>
nsh>
nsh> ls
/:
dev/
proc/
nsh> mount -t v9fs -o trans=virtio,tag=host /9p
nsh> ls
/:
9p/
dev/
proc/
nsh> ls 9p
/9p:
pass1/
.codespellrc
README.md
.gitignore
net/
build/
AUTHORS
sched/
Makefile
CONTRIBUTING.md
openamp/
ReleaseNotes
mm/
.editorconfig
.codespell-ignore-lines
LICENSE
.version
.yamllint
crypto/
drivers/
CMakeLists.txt
INVIOLABLES.md
arch/
syscall/
video/
.asf.yaml
boards/
audio/
Kconfig
include/
.git/
.gitmessage
binfmt/
NOTICE
tools/
cmake_out/
dummy/
libs/
fs/
.pre-commit-config.yaml
.github/
cmake/
Documentation/
graphics/
wireless/
nsh> ifconfig
eth0 Link encap:Ethernet HWaddr 00:e0:de:ad:be:ef at RUNNING mtu 1500
inet addr:10.0.2.15 DRaddr:10.0.2.2 Mask:255.255.255.0
IPv4 TCP UDP ICMP
Received 0000 0000 0000 0000
Dropped 0000 0000 0000 0000
IPv4 VHL: 0000 Frg: 0000
Checksum 0000 0000 0000 ----
TCP ACK: 0000 SYN: 0000
RST: 0000 0000
Type 0000 ---- ---- 0000
Sent 0000 0000 0000 0000
Rexmit ---- 0000 ---- ----
nsh>
nsh> iperf -s -i 1
IP: 10.0.2.15
mode=tcp-server sip=10.0.2.15:5001,dip=0.0.0.0:5001, interval=1, time=0
accept: 10.0.2.2:60720
Interval Transfer Bandwidth
0.00- 1.01 sec 9222196 Bytes 73.05 Mbits/sec
1.01- 2.02 sec 9433012 Bytes 74.72 Mbits/sec
2.02- 3.03 sec 9463248 Bytes 74.96 Mbits/sec
3.03- 4.04 sec 9453436 Bytes 74.88 Mbits/sec
4.04- 5.05 sec 9419736 Bytes 74.61 Mbits/sec
5.05- 6.06 sec 9451292 Bytes 74.86 Mbits/sec
6.06- 7.07 sec 9501272 Bytes 75.26 Mbits/sec
7.07- 8.08 sec 9452464 Bytes 74.87 Mbits/sec
8.08- 9.09 sec 9434036 Bytes 74.73 Mbits/sec
9.09- 10.10 sec 9404416 Bytes 74.49 Mbits/sec
closed by the peer: 10.0.2.2:60720
iperf exit
nsh>
nsh> uname -a
NuttX 12.10.0 ff74c26cdd9 Jan 30 2026 10:56:04 arm64 qemu-armv8a
nsh>
```
#### RPMSG VirtIO Test (Dual-Core QEMU)
```c
❯ qemu-system-aarch64 -cpu cortex-a53 -nographic \
-machine virt,virtualization=on,gic-version=3 \
-chardev stdio,id=con,mux=on -serial chardev:con \
-object
memory-backend-file,discard-data=on,id=shmmem-shmem0,mem-path=/dev/shm/my_shmem0,size=4194304,share=yes
\
-device ivshmem-plain,id=shmem0,memdev=shmmem-shmem0,addr=0xb \
-device virtio-serial-device,bus=virtio-mmio-bus.0 \
-chardev socket,path=/tmp/rpmsg_port_uart_socket,server=on,wait=off,id=foo \
-device virtconsole,chardev=foo \
-mon chardev=con,mode=readline -kernel ./nuttx/cmake_out/v8a_server/nuttx \
-gdb tcp::7775
[ 0.000000] [ 0] [ INFO] [server] pci_register_rptun_ivshmem_driver:
Register ivshmem driver, id=0, cpuname=proxy, master=1
[ 0.000000] [ 3] [ INFO] [server] pci_scan_bus: pci_scan_bus for bus 0
[ 0.000000] [ 3] [ INFO] [server] pci_scan_bus: class = 00000600,
hdr_type = 00000000
[ 0.000000] [ 3] [ INFO] [server] pci_scan_bus: 00:00 [1b36:0008]
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar0 set bad mask
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar1 set bad mask
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar2 set bad mask
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar3 set bad mask
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar4 set bad mask
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar5 set bad mask
[ 0.000000] [ 3] [ INFO] [server] pci_scan_bus: class = 00000200,
hdr_type = 00000000
[ 0.000000] [ 3] [ INFO] [server] pci_scan_bus: 00:08 [1af4:1000]
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar0:
mask64=fffffffe 32bytes
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar1:
mask64=fffffff0 4096bytes
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar2 set bad mask
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar3 set bad mask
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar4:
mask64=fffffffffffffff0 16384bytes
[ 0.000000] [ 3] [ INFO] [server] pci_scan_bus: class = 00000500,
hdr_type = 00000000
[ 0.000000] [ 3] [ INFO] [server] pci_scan_bus: 00:58 [1af4:1110]
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar0:
mask64=fffffff0 256bytes
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar1 set bad mask
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar2:
mask64=fffffffffffffff0 4194304bytes
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar4 set bad mask
[ 0.000000] [ 3] [ INFO] [server] pci_setup_device: pbar5 set bad mask
[ 0.000000] [ 3] [ INFO] [server] ivshmem_probe: shmem addr=0x8000400000
size=4194304 reg=0x10001000
[ 0.000000] [ 3] [ INFO] [server] rptun_ivshmem_probe: shmem
addr=0x8000400000 size=4194304
NuttShell (NSH) NuttX-12.10.0
server> [ 0.000000] [ 0] [ INFO] [proxy]
pci_register_rptun_ivshmem_driver: Register ivshmem driver, id=0,
cpuname=server, master=0
[ 0.000000] [ 3] [ INFO] [proxy] pci_scan_bus: pci_scan_bus for bus 0
[ 0.000000] [ 3] [ INFO] [proxy] pci_scan_bus: class = 00000600,
hdr_type = 00000000
[ 0.000000] [ 3] [ INFO] [proxy] pci_scan_bus: 00:00 [1b36:0008]
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar0 set bad mask
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar1 set bad mask
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar2 set bad mask
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar3 set bad mask
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar4 set bad mask
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar5 set bad mask
[ 0.000000] [ 3] [ INFO] [proxy] pci_scan_bus: class = 00000200,
hdr_type = 00000000
[ 0.000000] [ 3] [ INFO] [proxy] pci_scan_bus: 00:08 [1af4:1000]
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar0:
mask64=fffffffe 32bytes
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar1:
mask64=fffffff0 4096bytes
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar2 set bad mask
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar3 set bad mask
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar4:
mask64=fffffffffffffff0 16384bytes
[ 0.000000] [ 3] [ INFO] [proxy] pci_scan_bus: class = 00000500,
hdr_type = 00000000
[ 0.000000] [ 3] [ INFO] [proxy] pci_scan_bus: 00:58 [1af4:1110]
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar0:
mask64=fffffff0 256bytes
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar1 set bad mask
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar2:
mask64=fffffffffffffff0 4194304bytes
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar4 set bad mask
[ 0.000000] [ 3] [ INFO] [proxy] pci_setup_device: pbar5 set bad mask
[ 0.000000] [ 3] [ INFO] [proxy] ivshmem_probe: shmem addr=0x8000400000
size=4194304 reg=0x10001000
[ 0.000000] [ 3] [ INFO] [proxy] rptun_ivshmem_probe: shmem
addr=0x8000400000 size=4194304
[ 0.000000] [ 3] [ INFO] [proxy] rptun_ivshmem_probe: Start the wdog
server>
server>
server> ps
TID PID PPID PRI POLICY TYPE NPX STATE EVENT SIGMASK
STACK USED FILLED COMMAND
0 0 0 0 FIFO Kthread - Ready
0000000000000000 0008144 0001792 22.0% Idle_Task
1 0 0 192 FIFO Kthread - Waiting Semaphore
0000000000000000 0008080 0001328 16.4% hpwork 0x4047bc60 0x4047bce0
2 0 0 100 FIFO Kthread - Waiting Semaphore
0000000000000000 0008080 0001328 16.4% lpwork 0x4047bd10 0x4047bd90
5 0 0 224 FIFO Kthread - Waiting Semaphore
0000000000000000 0008080 0002224 27.5% rpmsg-uart-rx proxy2 0x404b1048
6 0 0 224 FIFO Kthread - Waiting Event
0000000000000000 0008080 0001968 24.3% rpmsg-uart-tx proxy2 0x404b1048
7 7 0 100 FIFO Task - Running
0000000000000000 0008112 0004176 51.4% nsh_main
8 0 0 224 FIFO Kthread - Waiting Semaphore
0000000000000000 0008080 0002208 27.3% rpmsg-virtio proxy 0x40495b38
server>
server>
server> rpmsg ping all 1 1 1 1
[ 0.000000] [ 7] [ EMERG] [server] ping times: 1
[ 0.000000] [ 7] [ EMERG] [server] buffer_len: 1520, send_len: 17
[ 0.000000] [ 7] [ EMERG] [server] avg: 0 s, 19125584 ns
[ 0.000000] [ 7] [ EMERG] [server] min: 0 s, 19125584 ns
[ 0.000000] [ 7] [ EMERG] [server] max: 0 s, 19125584 ns
[ 0.000000] [ 7] [ EMERG] [server] rate: 0.007110 Mbits/sec
[ 0.000000] [ 7] [ EMERG] [server] ping times: 1
[ 0.000000] [ 7] [ EMERG] [server] buffer_len: 2024, send_len: 17
[ 0.000000] [ 7] [ EMERG] [server] avg: 0 s, 18162928 ns
[ 0.000000] [ 7] [ EMERG] [server] min: 0 s, 18162928 ns
[ 0.000000] [ 7] [ EMERG] [server] max: 0 s, 18162928 ns
[ 0.000000] [ 7] [ EMERG] [server] rate: 0.007487 Mbits/sec
server> rpmsg dump all
[ 0.000000] [ 7] [ EMERG] [server] Local: server Remote: proxy Headrx 8
[ 0.000000] [ 7] [ EMERG] [server] Dump rpmsg info between cpu (master:
yes)server <==> proxy:
[ 0.000000] [ 7] [ EMERG] [server] rpmsg vq RX:
[ 0.000000] [ 7] [ EMERG] [server] rpmsg vq TX:
[ 0.000000] [ 7] [ EMERG] [server] rpmsg ept list:
[ 0.000000] [ 7] [ EMERG] [server] ept NS
[ 0.000000] [ 7] [ EMERG] [server] ept rpmsg-sensor
[ 0.000000] [ 7] [ EMERG] [server] ept rpmsg-ping
[ 0.000000] [ 7] [ EMERG] [server] ept rpmsg-syslog
[ 0.000000] [ 7] [ EMERG] [server] rpmsg buffer list:
[ 0.000000] [ 7] [ EMERG] [server] RX buffer, total 8, pending 0
[ 0.000000] [ 7] [ EMERG] [server] TX buffer, total 8, pending 0
[ 0.000000] [ 7] [ EMERG] [server] Remote: proxy2 state: 1
[ 0.000000] [ 7] [ EMERG] [server] ept NS
[ 0.000000] [ 7] [ EMERG] [server] ept rpmsg-sensor
[ 0.000000] [ 7] [ EMERG] [server] ept rpmsg-ping
[ 0.000000] [ 7] [ EMERG] [server] rpmsg_port queue RX: {used: 0, avail:
8}
[ 0.000000] [ 7] [ EMERG] [server] rpmsg buffer list:
[ 0.000000] [ 7] [ EMERG] [server] rpmsg_port queue TX: {used: 0, avail:
8}
[ 0.000000] [ 7] [ EMERG] [server] rpmsg buffer list:
[ 0.000000] [ 7] [ ALERT] [server] sched_dumpstack: backtrace| 5:
0x00000000402a8554 0x00000000402aa218 0x000000004029bfc8 0x000000004028ca54
0x00000000402e3b48 0x00000000402e3bf8 0x00000000402bca60 0x00000000402bcee8
[ 0.000000] [ 7] [ ALERT] [server] sched_dumpstack: backtrace| 5:
0x00000000402aced8
[ 0.000000] [ 7] [ ALERT] [server] sched_dumpstack: backtrace| 6:
0x00000000402a8974 0x00000000402f5c1c 0x00000000402bbe34 0x00000000402bcfd0
0x00000000402aced8
server>
server> uname -a
NuttX server 12.10.0 ff74c26cdd9-dirty Jan 30 2026 10:56:23 arm64 qemu-armv8a
server>
```
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