Re: [PATCH v2 13/14] OvmfPkg/QemuKernelLoaderFsDxe: add support for new Linux initrd device path

["Laszlo Ersek" <lersek@redhat.com>]

On 03/04/20 10:52, Ard Biesheuvel wrote:
> Linux v5.7 will introduce a new method to load the initial ramdisk
> (initrd) from the loader, using the LoadFile2 protocol installed on a
> special vendor GUIDed media device path.
> 
> Add support for this to our QEMU command line kernel/initrd loader.
> 
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2566
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c   | 79 ++++++++++++++++++++
>  OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf |  2 +
>  2 files changed, 81 insertions(+)
> 
> diff --git a/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c b/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c
> index 8ccb1983170c..f43b4c0db0ec 100644
> --- a/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c
> +++ b/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c
> @@ -13,15 +13,18 @@
>  #include <Guid/FileInfo.h>
>  #include <Guid/FileSystemInfo.h>
>  #include <Guid/FileSystemVolumeLabelInfo.h>
> +#include <Guid/LinuxEfiInitrdMedia.h>
>  #include <Guid/QemuKernelLoaderFsMedia.h>
>  #include <Library/BaseLib.h>
>  #include <Library/BaseMemoryLib.h>
>  #include <Library/DebugLib.h>
> +#include <Library/DevicePathLib.h>
>  #include <Library/MemoryAllocationLib.h>
>  #include <Library/QemuFwCfgLib.h>
>  #include <Library/UefiBootServicesTableLib.h>
>  #include <Library/UefiRuntimeServicesTableLib.h>
>  #include <Protocol/DevicePath.h>
> +#include <Protocol/LoadFile2.h>
>  #include <Protocol/SimpleFileSystem.h>
>  
>  //
> @@ -84,6 +87,19 @@ STATIC CONST SINGLE_VENMEDIA_NODE_DEVPATH mFileSystemDevicePath = {
>    }
>  };
>  
> +STATIC CONST SINGLE_VENMEDIA_NODE_DEVPATH mInitrdDevicePath = {
> +  {
> +    {
> +      MEDIA_DEVICE_PATH, MEDIA_VENDOR_DP,
> +      { sizeof (VENDOR_DEVICE_PATH) }
> +    },
> +    LINUX_EFI_INITRD_MEDIA_GUID
> +  }, {
> +    END_DEVICE_PATH_TYPE, END_ENTIRE_DEVICE_PATH_SUBTYPE,
> +    { sizeof (EFI_DEVICE_PATH_PROTOCOL) }
> +  }
> +};
> +
>  //
>  // The "file in the EFI stub filesystem" abstraction.
>  //
> @@ -839,6 +855,48 @@ STATIC CONST EFI_SIMPLE_FILE_SYSTEM_PROTOCOL mFileSystem = {
>    StubFileSystemOpenVolume
>  };
>  
> +STATIC
> +EFI_STATUS
> +EFIAPI
> +InitrdLoadFile2 (
> +  IN EFI_LOAD_FILE2_PROTOCOL          *This,
> +  IN EFI_DEVICE_PATH_PROTOCOL         *FilePath,
> +  IN BOOLEAN                          BootPolicy,
> +  IN OUT UINTN                        *BufferSize,

(1) You might want to beautify the columns here, similarly to commit
2632178bc683 ("OvmfPkg: add 'initrd' shell command to expose Linux
initrd via device path", 2020-03-04). Up to you.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks
Laszlo

> +  IN VOID                             *Buffer OPTIONAL
> +  )
> +{
> +  CONST KERNEL_BLOB   *InitrdBlob = &mKernelBlob[KernelBlobTypeInitrd];
> +
> +  ASSERT (InitrdBlob->Size > 0);
> +
> +  if (BootPolicy) {
> +    return EFI_UNSUPPORTED;
> +  }
> +
> +  if (BufferSize == NULL || !IsDevicePathValid (FilePath, 0)) {
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  if (FilePath->Type != END_DEVICE_PATH_TYPE ||
> +      FilePath->SubType != END_ENTIRE_DEVICE_PATH_SUBTYPE) {
> +    return EFI_NOT_FOUND;
> +  }
> +
> +  if (Buffer == NULL || *BufferSize < InitrdBlob->Size) {
> +    *BufferSize = InitrdBlob->Size;
> +    return EFI_BUFFER_TOO_SMALL;
> +  }
> +
> +  CopyMem (Buffer, InitrdBlob->Data, InitrdBlob->Size);
> +
> +  *BufferSize = InitrdBlob->Size;
> +  return EFI_SUCCESS;
> +}
> +
> +STATIC CONST EFI_LOAD_FILE2_PROTOCOL     mInitrdLoadFile2 = {
> +  InitrdLoadFile2,
> +};
>  
>  //
>  // Utility functions.
> @@ -949,6 +1007,7 @@ QemuKernelLoaderFsDxeEntrypoint (
>    KERNEL_BLOB               *KernelBlob;
>    EFI_STATUS                Status;
>    EFI_HANDLE                FileSystemHandle;
> +  EFI_HANDLE                InitrdLoadFile2Handle;
>  
>    if (!QemuFwCfgIsAvailable ()) {
>      return EFI_NOT_FOUND;
> @@ -993,8 +1052,28 @@ QemuKernelLoaderFsDxeEntrypoint (
>      goto FreeBlobs;
>    }
>  
> +  if (KernelBlob[KernelBlobTypeInitrd].Size > 0) {
> +    InitrdLoadFile2Handle = NULL;
> +    Status = gBS->InstallMultipleProtocolInterfaces (&InitrdLoadFile2Handle,
> +                    &gEfiDevicePathProtocolGuid,  &mInitrdDevicePath,
> +                    &gEfiLoadFile2ProtocolGuid,   &mInitrdLoadFile2,
> +                    NULL);
> +    if (EFI_ERROR (Status)) {
> +      DEBUG ((DEBUG_ERROR, "%a: InstallMultipleProtocolInterfaces(): %r\n",
> +        __FUNCTION__, Status));
> +      goto UninstallFileSystemHandle;
> +    }
> +  }
> +
>    return EFI_SUCCESS;
>  
> +UninstallFileSystemHandle:
> +  Status = gBS->UninstallMultipleProtocolInterfaces (FileSystemHandle,
> +                  &gEfiDevicePathProtocolGuid,       &mFileSystemDevicePath,
> +                  &gEfiSimpleFileSystemProtocolGuid, &mFileSystem,
> +                  NULL);
> +  ASSERT_EFI_ERROR (Status);
> +
>  FreeBlobs:
>    while (BlobType > 0) {
>      CurrentBlob = &mKernelBlob[--BlobType];
> diff --git a/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf b/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf
> index 5ba88063def0..7b35adb8e034 100644
> --- a/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf
> +++ b/OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.inf
> @@ -28,6 +28,7 @@ [LibraryClasses]
>    BaseLib
>    BaseMemoryLib
>    DebugLib
> +  DevicePathLib
>    MemoryAllocationLib
>    QemuFwCfgLib
>    UefiBootServicesTableLib
> @@ -42,6 +43,7 @@ [Guids]
>  
>  [Protocols]
>    gEfiDevicePathProtocolGuid                ## PRODUCES
> +  gEfiLoadFile2ProtocolGuid                 ## PRODUCES
>    gEfiSimpleFileSystemProtocolGuid          ## PRODUCES
>  
>  [Depex]
>