Support multiple virtio block devices

[ChinYikMing]

Demo Video

multiple-vblk.mp4

Problem Statement

Previously, #539 set VBLK_DEV_CNT_MAX to 1, limiting the virtual
machine to a single block device. This commit introduces support for
multiple block devices by switching from statically allocated storage to
dynamic allocation based on CLI input.

Key changes:

1. Dynamic Allocation
   Virtio block related fields are now dynamically allocated based on the
   number of -x vblk options provided.

2. Device Tree Generation
   The prewritten virtio@ subnode for block device in device/minimal.dts is
   commented and it can be an example subnode for future reference.
   load_dtb() dynamically appends virtio@ subnodes under the SoC node
   based on the number of block devices.

3. MMIO Handling
   Instead of hardcoding switch cases for each MMIO region of block device,
   the code now checks whether the accessed MMIO address falls within the
   valid range of any block device.

Note:
The /dev/vdx device order is assigned in reverse: the first -x vblk
argument corresponds to the device with the highest letter, while
subsequent arguments receive lower-lettered device names.

Testing Procedure

0. Clone the branch

$ git clone https://github.com/ChinYikMing/rv32emu.git -b multiple-vblk --depth 1 && cd rv32emu

1. Create 2 disk images (more than 2 is also OK, just adjusting the -x vblk option)

$ dd if=/dev/zero of=disk1.img bs=4M count=32
$ mkfs.ext4 disk1.img

$ dd if=/dev/zero of=disk2.img bs=4M count=32
$ mkfs.ext4 disk2.img

2. Build the emulator

$ make ENABLE_SYSTEM=1 INITRD_SIZE=32 -j8

3. Fetch Linux Image artifact

$ make artifact ENABLE_SYSTEM=1

4. Boot the guestOS with 2 block devices

$ build/rv32emu -k build/linux-image/Image -i build/linux-image/rootfs.cpio -x vblk:disk1.img -x vblk:disk2.img

5. Show multiple block devices in guestOS

# ls /dev/vd*

6. Mount both block devices in guestOS

# mkdir -p mnt && mount /dev/vda mnt
# mkdir -p mnt2 && mount /dev/vdb mnt2

7. Write some data into the block devices

# echo "rv32emu" > mnt/emu.txt
# echo "rv32emu" > mnt2/emu.txt

8. Cat the written data in the block devices

# cat mnt/emu.txt
# cat mnt2/emu.txt

Expected Result

# ls /dev/vd*
/dev/vda  /dev/vdb
# mkdir -p mnt && mount /dev/vda mnt
[   30.911107] EXT4-fs (vda): mounted filesystem with ordered data mode. Quota mode: disabled.
# mkdir -p mnt2 && mount /dev/vdb mnt2
[   39.067705] EXT4-fs (vdb): mounted filesystem with ordered data mode. Quota mode: disabled.
# echo "rv32emu" > mnt/emu.txt
# echo "rv32emu" > mnt2/emu.txt
# cat mnt/emu.txt
rv32emu
# cat mnt2/emu.txt
rv32emu
#

[jserv]

Benchmarks

Benchmark suite	Current: 9b4f2fe	Previous: 678c47a	Ratio
Dhrystone	1323 Average DMIPS over 10 runs	1290 Average DMIPS over 10 runs	0.98
Coremark	904.68 Average iterations/sec over 10 runs	913.951 Average iterations/sec over 10 runs	1.01

This comment was automatically generated by workflow using github-action-benchmark.

[visitorckw]

Nit: Since this variable represents a length, would size_t be more appropriate than int?