OvmfPkg/VirtioFsDxe: implement virtio device (un)initialization

Add the VirtioFsInit(), VirtioFsUninit(), and VirtioFsExitBoot()
functions.

In VirtioFsInit():

- Verify the host-side config of the virtio-fs device.

- Save the filesystem label ("tag") for later, from the configuration area
  of the virtio-fs device.

- Save the virtio queue size for later as well.

- Set up the virtio ring for sending requests.

In VirtioFsUninit():

- Reset the device.

- Tear down the virtio ring.

In VirtioFsExitBoot():

- Reset the device.

With this patch, the UEFI connect / disconnect controller operations
involve virtio setup / teardown; they are visible in the virtio-fs
daemon's log file. The virtiofsd log also confirms the device reset in
VirtioFsExitBoot(), when an OS is booted while the virtio-fs device is
bound.

Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3097
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20201216211125.19496-5-lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>

OvmfPkg/VirtioFsDxe/VirtioFsDxe.h

@@ -11,12 +11,21 @@
 #define VIRTIO_FS_DXE_H_
 
 #include <Base.h>                      // SIGNATURE_64()
+#include <IndustryStandard/VirtioFs.h> // VIRTIO_FS_TAG_BYTES
 #include <Library/DebugLib.h>          // CR()
 #include <Protocol/SimpleFileSystem.h> // EFI_SIMPLE_FILE_SYSTEM_PROTOCOL
 #include <Protocol/VirtioDevice.h>     // VIRTIO_DEVICE_PROTOCOL
+#include <Uefi/UefiBaseType.h>         // EFI_EVENT
 
 #define VIRTIO_FS_SIG SIGNATURE_64 ('V', 'I', 'R', 'T', 'I', 'O', 'F', 'S')
 
+//
+// Filesystem label encoded in UCS-2, transformed from the UTF-8 representation
+// in "VIRTIO_FS_CONFIG.Tag", and NUL-terminated. Only the printable ASCII code
+// points (U+0020 through U+007E) are supported.
+//
+typedef CHAR16 VIRTIO_FS_LABEL[VIRTIO_FS_TAG_BYTES + 1];
+
 //
 // Main context structure, expressing an EFI_SIMPLE_FILE_SYSTEM_PROTOCOL
 // interface on top of the Virtio Filesystem device.
@@ -31,12 +40,38 @@ typedef struct {
   //                              -----------   ------------------  ----------
   UINT64                          Signature; // DriverBindingStart  0
   VIRTIO_DEVICE_PROTOCOL          *Virtio;   // DriverBindingStart  0
+  VIRTIO_FS_LABEL                 Label;     // VirtioFsInit        1
+  UINT16                          QueueSize; // VirtioFsInit        1
+  VRING                           Ring;      // VirtioRingInit      2
+  VOID                            *RingMap;  // VirtioRingMap       2
+  EFI_EVENT                       ExitBoot;  // DriverBindingStart  0
   EFI_SIMPLE_FILE_SYSTEM_PROTOCOL SimpleFs;  // DriverBindingStart  0
 } VIRTIO_FS;
 
 #define VIRTIO_FS_FROM_SIMPLE_FS(SimpleFsReference) \
   CR (SimpleFsReference, VIRTIO_FS, SimpleFs, VIRTIO_FS_SIG);
 
+//
+// Initialization and helper routines for the Virtio Filesystem device.
+//
+
+EFI_STATUS
+VirtioFsInit (
+  IN OUT VIRTIO_FS *VirtioFs
+  );
+
+VOID
+VirtioFsUninit (
+  IN OUT VIRTIO_FS *VirtioFs
+  );
+
+VOID
+EFIAPI
+VirtioFsExitBoot (
+  IN EFI_EVENT ExitBootEvent,
+  IN VOID      *VirtioFsAsVoid
+  );
+
 //
 // EFI_SIMPLE_FILE_SYSTEM_PROTOCOL member functions for the Virtio Filesystem
 // driver.