Migrate virtio-blk from semu

This commit migrates @shengwen-tw's brilliant virtio implementation
from semu, with the following modification:

1. Rename virtio_blk_reg_read/write to virtio_blk_read/write
The original virtio_blk_read verified whether the virtio MMIO was
aligned to 4. Since rv32emu does not enforce alignment checks for UART
and PLIC devices or raise misalignment exceptions, this verification
has been omitted.

2. Implement MMIO_VIRTIOBLK

3. Implement vblk_new() and vblk_delete()
These functions align with the conventions used for UART and PLIC
devices.

4. Introduce new argument '-x vblk:<disk_image>' for virtio-blk disk
image

5. Fix the size of addr in virtq_desc structure.

Co-authored-by: Shengwen Cheng <[email protected]>

Makefile

@@ -195,7 +195,7 @@ endif
 # during emulator initialization.
 $(call set-feature, FULL4G)
 ifeq ($(call has, FULL4G), 1)
-$(OUT)/main.o: CFLAGS += -DMEM_SIZE=0xFFFFFFFFULL # 2^{32} - 1
+CFLAGS += -DMEM_SIZE=0xFFFFFFFFULL # 2^{32} - 1
 endif
 
 ENABLE_GDBSTUB ?= 0

README.md

@@ -77,7 +77,7 @@ $ make ENABLE_SYSTEM=1 system
 Build using run using specified images:
 ```shell
 $ make ENABLE_SYSTEM=1
-$ build/rv32emu -k <kernel_img_path> -i <rootfs_img_path>
+$ build/rv32emu -k <kernel_img_path> -i <rootfs_img_path> [-x vblk:<virtio_blk_img_path>]
 ```
 
 Build with a larger INITRD_SIZE (e.g., 64 MiB) to run SDL-oriented application because the default 8 MiB is insufficient for SDL-oriented application artifacts:
@@ -86,6 +86,21 @@ $ make system ENABLE_SYSTEM=1 ENABLE_SDL=1 INITRD_SIZE=64
 ```
 Once login the guestOS, run `doom-riscv` or `quake` or `smolnes`. To terminate SDL-oriented applications, use the built-in exit utility, ctrl-c or the SDL window close button(X).
 
+#### Virtio Block Device (optional)
+Generate ext4 image file for virtio block device in Unix-like system:
+```shell
+$ dd if=/dev/zero of=disk.img bs=4M count=32
+$ mkfs.ext4 disk.img
+```
+Mount the virtual block device and create a test file after booting, note that root privilege is required to mount and unmount a disk:
+```shell
+# mkdir mnt
+# mount /dev/vda mnt
+# echo "rv32emu" > mnt/emu.txt
+# umount mnt
+```
+Reboot and re-mount the virtual block device, the written file should remain existing.
+
 #### Build Linux image
 An automated build script is provided to compile the RISC-V cross-compiler, Busybox, and Linux kernel from source. Please note that it only supports the Linux host environment. It can be found at tools/build-linux-image.sh.
 ```

src/devices/minimal.dts

@@ -65,5 +65,11 @@
             no-loopback-test;
             clock-frequency = <5000000>; /* the baudrate divisor is ignored */
         };
+
+        blk0: virtio@4200000 {
+            compatible = "virtio,mmio";
+            reg = <0x4200000 0x200>;
+            interrupts = <3>;
+        };
     };
 };