Add support for readonly FLAT/ZERO VMDK format

Currently, it's mainly used for EROFS to merge hundreds of sub-blobs
(container image layers) into one block device to avoid having too
many block devices (and it would even be impossible for virtio-mmio
since legacy IRQs is much limited in libkrun).

Why VMDK is useful?  Since it seems to be the only standard and simple
way to support one-single block device that consists of a collection of
multiple file parts among popular virtualization products such as QEMU
and VirtualBox.

Update the `krun_add_disk2` API to specify the VMDK format:
 - KRUN_DISK_FORMAT_VMDK

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Author: hsiangkao

Cargo.lock

@@ -167,6 +167,9 @@ int32_t krun_add_disk(uint32_t ctx_id, const char *block_id, const char *disk_pa
 /* Supported disk image formats */
 #define KRUN_DISK_FORMAT_RAW 0
 #define KRUN_DISK_FORMAT_QCOW2 1
+/* Note: Only supports FLAT/ZERO formats without delta links */
+#define KRUN_DISK_FORMAT_VMDK 2
+
 /**
  * Adds a disk image to be used as a general partition for the microVM. The supported
  * image formats are: "raw" and "qcow2".

include/libkrun.h

@@ -38,7 +38,7 @@ arch = { path = "../arch" }
 utils = { path = "../utils" }
 polly = { path = "../polly" }
 rutabaga_gfx = { path = "../rutabaga_gfx", features = ["virgl_renderer", "virgl_renderer_next"], optional = true }
-imago = { version = "0.1.5", features = ["sync-wrappers", "vm-memory"] }
+imago = { features = ["sync-wrappers", "vm-memory"], git = "https://gitlab.com/hreitz/imago.git", branch = "main" }
 
 [target.'cfg(target_os = "macos")'.dependencies]
 hvf = { path = "../hvf" }

src/devices/Cargo.toml

@@ -19,8 +19,8 @@ use std::sync::Arc;
 use std::thread::JoinHandle;
 
 use imago::{
-    file::File as ImagoFile, qcow2::Qcow2, raw::Raw, DynStorage, Storage, StorageOpenOptions,
-    SyncFormatAccess,
+    file::File as ImagoFile, qcow2::Qcow2, raw::Raw, vmdk::Vmdk, DynStorage, FormatDriverBuilder,
+    PermissiveImplicitOpenGate, Storage, StorageOpenOptions, SyncFormatAccess,
 };
 use log::{error, warn};
 use utils::eventfd::{EventFd, EFD_NONBLOCK};
@@ -240,6 +240,13 @@ impl Block {
                 )?;
                 SyncFormatAccess::new(raw)?
             }
+            ImageType::Vmdk => {
+                let vmdk = Vmdk::<Box<dyn DynStorage>, Arc<imago::FormatAccess<_>>>::builder(
+                    Box::new(file),
+                )
+                .open_sync(PermissiveImplicitOpenGate::default())?;
+                SyncFormatAccess::new(vmdk)?
+            }
         };
 
         let disk_image = Arc::new(disk_image);

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

@@ -38,4 +38,5 @@ pub enum Error {
 pub enum ImageType {
     Raw,
     Qcow2,
+    Vmdk,
 }

src/devices/src/virtio/block/mod.rs

@@ -703,6 +703,7 @@ pub unsafe extern "C" fn krun_add_disk2(
     let format = match disk_format {
         0 => ImageType::Raw,
         1 => ImageType::Qcow2,
+        2 => ImageType::Vmdk,
         _ => {
             // Do not continue if the user cannot specify a valid disk format
             return -libc::EINVAL;