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/DriverBinding.c

@@ -6,7 +6,6 @@
   SPDX-License-Identifier: BSD-2-Clause-Patent
 **/
 
-#include <IndustryStandard/Virtio.h>          // VIRTIO_SUBSYSTEM_FILESYSTEM
 #include <Library/BaseLib.h>                  // AsciiStrCmp()
 #include <Library/MemoryAllocationLib.h>      // AllocatePool()
 #include <Library/UefiBootServicesTableLib.h> // gBS
@@ -80,6 +79,17 @@ VirtioFsBindingStart (
     goto FreeVirtioFs;
   }
 
+  Status = VirtioFsInit (VirtioFs);
+  if (EFI_ERROR (Status)) {
+    goto CloseVirtio;
+  }
+
+  Status = gBS->CreateEvent (EVT_SIGNAL_EXIT_BOOT_SERVICES, TPL_CALLBACK,
+                  VirtioFsExitBoot, VirtioFs, &VirtioFs->ExitBoot);
+  if (EFI_ERROR (Status)) {
+    goto UninitVirtioFs;
+  }
+
   VirtioFs->SimpleFs.Revision   = EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_REVISION;
   VirtioFs->SimpleFs.OpenVolume = VirtioFsOpenVolume;
 
@@ -87,11 +97,18 @@ VirtioFsBindingStart (
                   &gEfiSimpleFileSystemProtocolGuid, EFI_NATIVE_INTERFACE,
                   &VirtioFs->SimpleFs);
   if (EFI_ERROR (Status)) {
-    goto CloseVirtio;
+    goto CloseExitBoot;
   }
 
   return EFI_SUCCESS;
 
+CloseExitBoot:
+  CloseStatus = gBS->CloseEvent (VirtioFs->ExitBoot);
+  ASSERT_EFI_ERROR (CloseStatus);
+
+UninitVirtioFs:
+  VirtioFsUninit (VirtioFs);
+
 CloseVirtio:
   CloseStatus = gBS->CloseProtocol (ControllerHandle,
                        &gVirtioDeviceProtocolGuid, This->DriverBindingHandle,
@@ -133,6 +150,11 @@ VirtioFsBindingStop (
     return Status;
   }
 
+  Status = gBS->CloseEvent (VirtioFs->ExitBoot);
+  ASSERT_EFI_ERROR (Status);
+
+  VirtioFsUninit (VirtioFs);
+
   Status = gBS->CloseProtocol (ControllerHandle, &gVirtioDeviceProtocolGuid,
                   This->DriverBindingHandle, ControllerHandle);
   ASSERT_EFI_ERROR (Status);