Support multiple virtio block devices

ChinYikMing · ChinYikMing · commit ee4cb919ccf5 · 2025-08-31T04:47:14.000+08:00
Previously, sysprog21#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.
diff --git a/mk/system.mk b/mk/system.mk
@@ -29,6 +29,8 @@ $(BUILD_DTB2C): $(BIN_TO_C) $(BUILD_DTB)
 	$(VECHO) "  BIN2C\t$@\n"
 	$(Q)$(BIN_TO_C) $(BUILD_DTB) > $@
 
+MMIO_TMPL := src/devices/mmio_template.h
+
 $(DEV_OUT)/%.o: $(DEV_SRC)/%.c $(deps_emcc)
 	$(Q)mkdir -p $(DEV_OUT)
 	$(VECHO) "  CC\t$@\n"
diff --git a/src/devices/minimal.dts b/src/devices/minimal.dts
@@ -66,10 +66,14 @@
             clock-frequency = <5000000>; /* the baudrate divisor is ignored */
         };
 
-        blk0: virtio@4200000 {
+        /*
+         * Virtio block example subnode
+         * The actual subnode are generated dynamically depends on the CLI -x vblk option
+         */
+        /*blk0: virtio@4100000 {
             compatible = "virtio,mmio";
-            reg = <0x4200000 0x200>;
-            interrupts = <3>;
-        };
+            reg = <0x4100000 0x200>;
+            interrupts = <2>;
+        };*/
     };
 };
diff --git a/src/devices/virtio-blk.c b/src/devices/virtio-blk.c
@@ -33,7 +33,7 @@
 #define DISK_BLK_SIZE 512
 
 /* TODO: Enable mutiple virtio-blk devices. */
-#define VBLK_DEV_CNT_MAX 1
+#define VBLK_DEV_CNT_MAX 3
 
 #define VBLK_FEATURES_0 0
 #define VBLK_FEATURES_1 1 /* VIRTIO_F_VERSION_1 */
@@ -81,9 +81,6 @@ PACKED(struct vblk_req_header {
     uint8_t status;
 });
 
-static struct virtio_blk_config vblk_configs[VBLK_DEV_CNT_MAX];
-static int vblk_dev_cnt = 0;
-
 static void virtio_blk_set_fail(virtio_blk_state_t *vblk)
 {
     vblk->status |= VIRTIO_STATUS_DEVICE_NEEDS_RESET;
@@ -401,20 +398,16 @@ uint32_t *virtio_blk_init(virtio_blk_state_t *vblk,
                           char *disk_file,
                           bool readonly)
 {
-    if (vblk_dev_cnt >= VBLK_DEV_CNT_MAX) {
-        rv_log_error(
-            "Exceeded the number of virtio-blk devices that can be allocated");
-        exit(EXIT_FAILURE);
-    }
-
     /*
      * For mmap_fallback, if vblk is not specified, disk_fd should remain -1 and
      * no fsync should be performed on exit.
      */
+
     vblk->disk_fd = -1;
 
     /* Allocate memory for the private member */
-    vblk->priv = &vblk_configs[vblk_dev_cnt++];
+    vblk->priv = calloc(1, sizeof(struct virtio_blk_config));
+    assert(vblk->priv);
 
     /* No disk image is provided */
     if (!disk_file) {
@@ -549,5 +542,6 @@ void vblk_delete(virtio_blk_state_t *vblk)
     else
         munmap(vblk->disk, VBLK_PRIV(vblk)->disk_size);
 #endif
+    free(vblk->priv);
     free(vblk);
 }
diff --git a/src/devices/virtio.h b/src/devices/virtio.h
@@ -76,8 +76,7 @@ struct virtq_desc {
     uint16_t next;
 };
 
-#define IRQ_VBLK_SHIFT 3
-#define IRQ_VBLK_BIT (1 << IRQ_VBLK_SHIFT)
+#define IRQ_VBLK_BIT(base, i) (1 << (base + i))
 
 typedef struct {
     uint32_t queue_num;
diff --git a/src/main.c b/src/main.c
@@ -60,7 +60,10 @@ static char *prof_out_file;
 static char *opt_kernel_img;
 static char *opt_rootfs_img;
 static char *opt_bootargs;
-static char *opt_virtio_blk_img;
+/* FIXME: handle overflow */
+#define VBLK_DEV_MAX 100
+static char *opt_virtio_blk_img[VBLK_DEV_MAX];
+static int opt_virtio_blk_idx = 0;
 #endif
 
 static void print_usage(const char *filename)
@@ -78,7 +81,8 @@ static void print_usage(const char *filename)
 #if RV32_HAS(SYSTEM) && !RV32_HAS(ELF_LOADER)
         "  -k <image> : use <image> as kernel image\n"
         "  -i <image> : use <image> as rootfs\n"
-        "  -x vblk:<image>[,readonly] : use <image> as virtio-blk disk image "
+        "  -x vblk:<image>[,readonly] [-x vblk:<image>[,readonly]]: use "
+        "<image> as virtio-blk disk image "
         "(default read and write)\n"
         "  -b <bootargs> : use customized <bootargs> for the kernel\n"
 #endif
@@ -127,7 +131,8 @@ static bool parse_args(int argc, char **args)
             break;
         case 'x':
             if (!strncmp("vblk:", optarg, 5))
-                opt_virtio_blk_img = optarg + 5; /* strlen("vblk:") */
+                opt_virtio_blk_img[opt_virtio_blk_idx++] =
+                    optarg + 5; /* strlen("vblk:") */
             else
                 return false;
             emu_argc++;
@@ -273,7 +278,12 @@ int main(int argc, char **args)
     attr.data.system.kernel = opt_kernel_img;
     attr.data.system.initrd = opt_rootfs_img;
     attr.data.system.bootargs = opt_bootargs;
-    attr.data.system.vblk_device = opt_virtio_blk_img;
+    if (opt_virtio_blk_idx) {
+        attr.data.system.vblk_device = opt_virtio_blk_img;
+        attr.data.system.vblk_device_cnt = opt_virtio_blk_idx;
+    } else {
+        attr.data.system.vblk_device = NULL;
+    }
 #else
     attr.data.user.elf_program = opt_prog_name;
 #endif
diff --git a/src/riscv.c b/src/riscv.c
@@ -293,14 +293,26 @@ static void load_dtb(char **ram_loc, vm_attr_t *attr)
 {
 #include "minimal_dtb.h"
     char *bootargs = attr->data.system.bootargs;
-    char *vblk = attr->data.system.vblk_device;
+    char **vblk = attr->data.system.vblk_device;
     char *blob = *ram_loc;
     char *buf;
     size_t len;
     int node, err;
     int totalsize;
 
-    memcpy(blob, minimal, sizeof(minimal));
+#define DTB_EXPAND_SIZE 1024  // or more if needed
+
+    /* Allocate enough memory for DTB + extra room */
+    int minimal_len = ARRAY_SIZE(minimal);
+    void *dtb_buf = calloc(minimal_len + DTB_EXPAND_SIZE, sizeof(uint8_t));
+    assert(dtb_buf);
+
+    /* Expand it to a usable DTB blob */
+    err = fdt_open_into(minimal, dtb_buf, minimal_len + DTB_EXPAND_SIZE);
+    if (err < 0) {
+        rv_log_error("fdt_open_into fails\n");
+        exit(EXIT_FAILURE);
+    }
 
     if (bootargs) {
         node = fdt_path_offset(blob, "/chosen");
@@ -320,18 +332,71 @@ static void load_dtb(char **ram_loc, vm_attr_t *attr)
         assert(!err);
     }
 
-    /* remove the vblk node from soc if it is not specified */
-    if (!vblk) {
-        int subnode;
-        node = fdt_path_offset(blob, "/soc@F0000000");
+    if (vblk) {
+        int node = fdt_path_offset(dtb_buf, "/soc@F0000000");
         assert(node >= 0);
 
-        subnode = fdt_subnode_offset(blob, node, "virtio@4200000");
-        assert(subnode >= 0);
+        uint32_t base_addr = 0x4000000;
+        uint32_t addr_offset = 0x100000;
+        uint32_t size = 0x200;
+
+        uint32_t next_addr = base_addr;
+        uint32_t next_irq = 1;
+
+        // scan existing nodes to get next addr and irq
+        int subnode;
+        fdt_for_each_subnode(subnode, dtb_buf, node)
+        {
+            const char *name = fdt_get_name(dtb_buf, subnode, NULL);
+            assert(name);
+
+            uint32_t addr = strtoul(name + 7, NULL, 16);
+            if (addr == next_addr)
+                next_addr = addr + addr_offset;
+
+            const fdt32_t *irq_prop =
+                fdt_getprop(dtb_buf, subnode, "interrupts", NULL);
+            if (irq_prop) {
+                uint32_t irq = fdt32_to_cpu(*irq_prop);
+                if (irq == next_irq)
+                    next_irq = irq + 1;
+            }
+        }
+        /* set IRQ for virtio block, see devices/virtio.h */
+        attr->vblk_irq_base = next_irq;
+
+        /* adding new virtio block nodes */
+        for (int i = 0; i < attr->vblk_cnt; i++) {
+            uint32_t new_addr = next_addr + i * addr_offset;
+            uint32_t new_irq = next_irq + i;
+
+            char node_name[32];
+            snprintf(node_name, sizeof(node_name), "virtio@%x", new_addr);
+
+            int subnode = fdt_add_subnode(dtb_buf, node, node_name);
+            if (subnode == -FDT_ERR_NOSPACE) {
+                rv_log_warn("add subnode no space!\n");
+            }
+            assert(subnode >= 0);
+
+            /* compatible = "virtio,mmio" */
+            assert(fdt_setprop_string(dtb_buf, subnode, "compatible",
+                                      "virtio,mmio") == 0);
+
+            /* reg = <new_addr size> */
+            uint32_t reg[2] = {cpu_to_fdt32(new_addr), cpu_to_fdt32(size)};
+            assert(fdt_setprop(dtb_buf, subnode, "reg", reg, sizeof(reg)) == 0);
 
-        assert(fdt_del_node(blob, subnode) == 0);
+            /* interrupts = <new_irq> */
+            uint32_t irq = cpu_to_fdt32(new_irq);
+            assert(fdt_setprop(dtb_buf, subnode, "interrupts", &irq,
+                               sizeof(irq)) == 0);
+        }
     }
 
+    memcpy(blob, dtb_buf, minimal_len + DTB_EXPAND_SIZE);
+    free(dtb_buf);
+
     totalsize = fdt_totalsize(blob);
     *ram_loc += totalsize;
     return;
@@ -406,28 +471,36 @@ static void rv_fsync_device()
      *
      * vblk is optional, so it could be NULL
      */
-    if (attr->vblk) {
-        if (attr->vblk->disk_fd >= 3) {
-            if (attr->vblk->device_features & VIRTIO_BLK_F_RO) /* readonly */
-                goto end;
-
-            if (pwrite(attr->vblk->disk_fd, attr->vblk->disk,
-                       attr->vblk->disk_size, 0) == -1) {
-                rv_log_error("pwrite block device failed: %s", strerror(errno));
-                return;
+    if (attr->vblk_cnt) {
+        for (int i = 0; i < attr->vblk_cnt; i++) {
+            virtio_blk_state_t *vblk = attr->vblk[i];
+            if (vblk->disk_fd >= 3) {
+                if (vblk->device_features & VIRTIO_BLK_F_RO) /* readonly */
+                    goto end;
+
+                if (pwrite(vblk->disk_fd, vblk->disk, vblk->disk_size, 0) ==
+                    -1) {
+                    rv_log_error("pwrite block device failed: %s",
+                                 strerror(errno));
+                    return;
+                }
+
+                if (fsync(vblk->disk_fd) == -1) {
+                    rv_log_error("fsync block device failed: %s",
+                                 strerror(errno));
+                    return;
+                }
+                rv_log_info("Sync block device OK");
+
+            end:
+                close(vblk->disk_fd);
             }
 
-            if (fsync(attr->vblk->disk_fd) == -1) {
-                rv_log_error("fsync block device failed: %s", strerror(errno));
-                return;
-            }
-            rv_log_info("Sync block device OK");
-
-        end:
-            close(attr->vblk->disk_fd);
+            vblk_delete(vblk);
         }
 
-        vblk_delete(attr->vblk);
+        free(attr->vblk);
+        free(attr->disk);
     }
 }
 #endif /* RV32_HAS(SYSTEM) && !RV32_HAS(ELF_LOADER) */
@@ -548,6 +621,9 @@ riscv_t *rv_create(riscv_user_t rv_attr)
      * *----------------*----------------*-------*
      */
 
+    /* load_dtb needs the count to add the virtio block subnode dynamically */
+    attr->vblk_cnt = attr->data.system.vblk_device_cnt;
+
     char *ram_loc = (char *) attr->mem->mem_base;
     map_file(&ram_loc, attr->data.system.kernel);
     rv_log_info("Kernel loaded");
@@ -590,36 +666,49 @@ riscv_t *rv_create(riscv_user_t rv_attr)
     attr->uart->out_fd = attr->fd_stdout;
 
     /* setup virtio-blk */
-    attr->vblk = NULL;
-    if (attr->data.system.vblk_device) {
+    attr->vblk_mmio_base_hi = 0x41;
+    attr->vblk_mmio_max_hi = attr->vblk_mmio_base_hi + attr->vblk_cnt;
+
+    rv_log_warn("0x%x 0x%x", attr->vblk_mmio_base_hi, attr->vblk_mmio_max_hi);
+
+    attr->vblk = malloc(sizeof(virtio_blk_state_t *) * attr->vblk_cnt);
+    assert(attr->vblk);
+    attr->disk = malloc(sizeof(uint32_t *) * attr->vblk_cnt);
+    assert(attr->disk);
+
+    if (attr->vblk_cnt) {
+        for (int i = 0; i < attr->vblk_cnt; i++) {
 /* Currently, only used for block image path and permission */
 #define MAX_OPTS 2
-        char *vblk_opts[MAX_OPTS] = {NULL};
-        int vblk_opt_idx = 0;
-        char *opt = strtok(attr->data.system.vblk_device, ",");
-        while (opt) {
-            if (vblk_opt_idx == MAX_OPTS) {
-                rv_log_error("Too many arguments for vblk");
-                break;
+            char *vblk_device_str = attr->data.system.vblk_device[i];
+            char *vblk_opts[MAX_OPTS] = {NULL};
+            int vblk_opt_idx = 0;
+            char *opt = strtok(vblk_device_str, ",");
+            while (opt) {
+                if (vblk_opt_idx == MAX_OPTS) {
+                    rv_log_error("Too many arguments for vblk");
+                    break;
+                }
+                vblk_opts[vblk_opt_idx++] = opt;
+                opt = strtok(NULL, ",");
             }
-            vblk_opts[vblk_opt_idx++] = opt;
-            opt = strtok(NULL, ",");
-        }
-        char *vblk_device = vblk_opts[0];
-        char *vblk_readonly = vblk_opts[1];
-
-        bool readonly = false;
-        if (vblk_readonly) {
-            if (strcmp(vblk_readonly, "readonly") != 0) {
-                rv_log_error("Unknown vblk option: %s", vblk_readonly);
-                exit(EXIT_FAILURE);
+            char *vblk_device = vblk_opts[0];
+            char *vblk_readonly = vblk_opts[1];
+
+            bool readonly = false;
+            if (vblk_readonly) {
+                if (strcmp(vblk_readonly, "readonly") != 0) {
+                    rv_log_error("Unknown vblk option: %s", vblk_readonly);
+                    exit(EXIT_FAILURE);
+                }
+                readonly = true;
             }
-            readonly = true;
-        }
 
-        attr->vblk = vblk_new();
-        attr->vblk->ram = (uint32_t *) attr->mem->mem_base;
-        attr->disk = virtio_blk_init(attr->vblk, vblk_device, readonly);
+            attr->vblk[i] = vblk_new();
+            attr->vblk[i]->ram = (uint32_t *) attr->mem->mem_base;
+            attr->disk[i] =
+                virtio_blk_init(attr->vblk[i], vblk_device, readonly);
+        }
     }
 
     capture_keyboard_input();
diff --git a/src/riscv.h b/src/riscv.h
diff --git a/src/system.c b/src/system.c
diff --git a/src/system.h b/src/system.h
