block: add read-only VMDK disk image support

resources/seccomp/aarch64-unknown-linux-musl.json

@@ -89,6 +89,14 @@
                 "syscall": "lseek",
                 "comment": "Used by the block device"
             },
+            {
+                "syscall": "preadv",
+                "comment": "Used by the imago VMDK disk image backend"
+            },
+            {
+                "syscall": "pwritev",
+                "comment": "Used by the imago VMDK disk image backend"
+            },
             {
                 "syscall": "mremap",
                 "comment": "Used for re-allocating large memory regions, for example vectors"

resources/seccomp/x86_64-unknown-linux-musl.json

@@ -89,6 +89,14 @@
                 "syscall": "lseek",
                 "comment": "Used by the block device"
             },
+            {
+                "syscall": "preadv",
+                "comment": "Used by the imago VMDK disk image backend"
+            },
+            {
+                "syscall": "pwritev",
+                "comment": "Used by the imago VMDK disk image backend"
+            },
             {
                 "syscall": "mremap",
                 "comment": "Used for re-allocating large memory regions, for example vectors"

src/vmm/Cargo.toml

@@ -58,6 +58,8 @@ vm-memory = { version = "0.17.1", features = [
 vm-superio = "0.8.1"
 vmm-sys-util = { version = "0.15.0", features = ["with-serde"] }
 zerocopy = { version = "0.8.40" }
+imago = { git = "https://gitlab.com/hreitz/imago", tag = "v0.2.2", features = ["sync-wrappers"] }
+tokio = { version = "1", features = ["rt"] }
 
 [target.'cfg(target_arch = "aarch64")'.dependencies]
 vm-fdt = "0.3.0"

src/vmm/src/devices/virtio/block/virtio/device.rs

@@ -96,13 +96,31 @@ impl DiskProperties {
         file_engine_type: FileEngineType,
     ) -> Result<Self, VirtioBlockError> {
         let mut disk_image = Self::open_file(&disk_image_path, is_disk_read_only)?;
-        let disk_size = Self::file_size(&disk_image_path, &mut disk_image)?;
         let image_id = Self::build_disk_image_id(&disk_image);
 
+        // Detect disk format and create the appropriate engine.
+        let format = block_io::detect_disk_format(&disk_image)
+            .map_err(|e| VirtioBlockError::BackingFile(e, disk_image_path.clone()))?;
+
+        let (file_engine, disk_size) = match format {
+            block_io::DiskImageFormat::Vmdk => {
+                // VMDK images are always read-only; the VmdkFileEngine enforces this.
+                let vmdk_engine = block_io::VmdkFileEngine::from_file(disk_image)
+                    .map_err(|e| VirtioBlockError::FileEngine(block_io::BlockIoError::Vmdk(e)))?;
+                let disk_size = vmdk_engine.disk_size();
+                (FileEngine::Vmdk(vmdk_engine), disk_size)
+            }
+            block_io::DiskImageFormat::Raw => {
+                let disk_size = Self::file_size(&disk_image_path, &mut disk_image)?;
+                let engine = FileEngine::from_file(disk_image, file_engine_type)
+                    .map_err(VirtioBlockError::FileEngine)?;
+                (engine, disk_size)
+            }
+        };
+
         Ok(Self {
             file_path: disk_image_path,
-            file_engine: FileEngine::from_file(disk_image, file_engine_type)
-                .map_err(VirtioBlockError::FileEngine)?,
+            file_engine,
             nsectors: disk_size >> SECTOR_SHIFT,
             image_id,
         })
@@ -118,10 +136,11 @@ impl DiskProperties {
         let disk_size = Self::file_size(&disk_image_path, &mut disk_image)?;
 
         self.image_id = Self::build_disk_image_id(&disk_image);
-        self.file_engine
+        let engine_disk_size = self
+            .file_engine
             .update_file_path(disk_image)
             .map_err(VirtioBlockError::FileEngine)?;
-        self.nsectors = disk_size >> SECTOR_SHIFT;
+        self.nsectors = engine_disk_size.unwrap_or(disk_size) >> SECTOR_SHIFT;
         self.file_path = disk_image_path;
 
         Ok(())
@@ -271,7 +290,7 @@ macro_rules! unwrap_async_file_engine_or_return {
     ($file_engine: expr) => {
         match $file_engine {
             FileEngine::Async(engine) => engine,
-            FileEngine::Sync(_) => {
+            FileEngine::Sync(_) | FileEngine::Vmdk(_) => {
                 error!("The block device doesn't use an async IO engine");
                 return;
             }
@@ -290,6 +309,8 @@ impl VirtioBlock {
             config.file_engine_type,
         )?;
 
+        let is_read_only = config.is_read_only;
+
         let rate_limiter = config
             .rate_limiter
             .map(RateLimiterConfig::try_into)
@@ -303,7 +324,7 @@ impl VirtioBlock {
             avail_features |= 1u64 << VIRTIO_BLK_F_FLUSH;
         }
 
-        if config.is_read_only {
+        if is_read_only {
             avail_features |= 1u64 << VIRTIO_BLK_F_RO;
         };
 
@@ -329,7 +350,7 @@ impl VirtioBlock {
             partuuid: config.partuuid,
             cache_type: config.cache_type,
             root_device: config.is_root_device,
-            read_only: config.is_read_only,
+            read_only: is_read_only,
 
             disk: disk_properties,
             rate_limiter,
@@ -559,6 +580,7 @@ impl VirtioBlock {
         match self.disk.file_engine {
             FileEngine::Sync(_) => FileEngineType::Sync,
             FileEngine::Async(_) => FileEngineType::Async,
+            FileEngine::Vmdk(_) => FileEngineType::Sync,
         }
     }