[PATCH] efi: bump efistub version from 1.1 to 3.0 for VZLinuxBootLoader compatibility

[Akihiro Suda]

- LINUX_EFISTUB_MAJOR_VERSION is bumped from 1 (0b1) to 3 (0b11).
  The value is now a bitfield. The next version will be 7 (0b111).

- LINUX_EFISTUB_MINOR_VERSION is pinned to 0x0, because Apple's
  VZLinuxBootLoader [1] cannot boot a kernel with other minor version value [2],
  even though it does not use UEFI. Tested with macOS 13.4 (x86_64).

[1] https://developer.apple.com/documentation/virtualization/vzlinuxbootloader
[2] https://lore.kernel.org/linux-efi/CAG8fp8Teu4G9JuenQrqGndFt2Gy+V4YgJ=hN1xX7AD940YKf3A@xxxxxxxxxxxxxx/

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217485
Signed-off-by: Akihiro Suda <akihiro.suda.cz@xxxxxxxxxxxxx>
---
 include/linux/pe.h | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/include/linux/pe.h b/include/linux/pe.h
index 5e1e11540870..ee5ade19b7eb 100644
--- a/include/linux/pe.h
+++ b/include/linux/pe.h
@@ -27,9 +27,25 @@
  * On x86, LoadImage() and StartImage() can be omitted if the EFI handover
  * protocol is implemented, which can be inferred from the version,
  * handover_offset and xloadflags fields in the bootparams structure.
+ *
+ * Linux EFI stub v1.1 unconditionally enabled initrd command line loader,
+ * which was previously gated by CONFIG_EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER.
+ *
+ * Linux EFI stub v3.0 changed the major version to be a bitfield (0b11).
+ * The rightmost bit means that it is compatible with v1.0 at least.
+ * The second rightmost bit means that initrd command line loader is enabled.
+ * So, there is no v2.0 (0b10), and the next version will be v7.0 (0b111).
+ */
+#define LINUX_EFISTUB_MAJOR_VERSION            0x3
+
+/*
+ * LINUX_EFISTUB_MINOR_VERSION is pinned to 0x0, because Apple's
+ * VZLinuxBootLoader cannot boot a kernel with other minor version value, even
+ * though it does not use UEFI. Tested with macOS 13.4 (x86_64).
+ *
+ * https://lore.kernel.org/linux-efi/CAG8fp8Teu4G9JuenQrqGndFt2Gy+V4YgJ=hN1xX7AD940YKf3A@xxxxxxxxxxxxxx/
  */
-#define LINUX_EFISTUB_MAJOR_VERSION            0x1
-#define LINUX_EFISTUB_MINOR_VERSION            0x1
+#define LINUX_EFISTUB_MINOR_VERSION            0x0

 /*
  * LINUX_PE_MAGIC appears at offset 0x38 into the MS-DOS header of EFI bootable
-- 
2.39.2