Patch "efi/bgrt: Skip efi_bgrt_init() in case of non-EFI boot" has been added to the 4.11-stable tree

This is a note to let you know that I've just added the patch titled

efi/bgrt: Skip efi_bgrt_init() in case of non-EFI boot

to the 4.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
efi-bgrt-skip-efi_bgrt_init-in-case-of-non-efi-boot.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Dave Young <[email protected]>
Date: Fri, 26 May 2017 12:36:51 +0100
Subject: efi/bgrt: Skip efi_bgrt_init() in case of non-EFI boot

From: Dave Young <[email protected]>

commit 7425826f4f7ac60f2538b06a7f0a5d1006405159 upstream.

Sabrina Dubroca reported an early panic:

  BUG: unable to handle kernel paging request at ffffffffff240001
  IP: efi_bgrt_init+0xdc/0x134

[...]

  ---[ end Kernel panic - not syncing: Attempted to kill the idle task!

... which was introduced by:

7b0a911478c7 ("efi/x86: Move the EFI BGRT init code to early init code")

The cause is that on this machine the firmware provides the EFI ACPI BGRT table even on legacy non-EFI bootups - which table should be EFI only.

The garbage BGRT data causes the efi_bgrt_init() panic.

Add a check to skip efi_bgrt_init() in case non-EFI bootup to work around this firmware bug.

---
 arch/x86/platform/efi/efi-bgrt.c |    3 +++
 1 file changed, 3 insertions(+)

@@ -36,6 +36,9 @@ void __init efi_bgrt_init(struct acpi_ta
 	if (acpi_disabled)
 		return;
 
+	if (!efi_enabled(EFI_BOOT))
+		return;
+
 	if (table->length < sizeof(bgrt_tab)) {
 		pr_notice("Ignoring BGRT: invalid length %u (expected %zu)\n",
 		       table->length, sizeof(bgrt_tab));

Patches currently in stable-queue which might be from [email protected] are

queue-4.11/efi-bgrt-skip-efi_bgrt_init-in-case-of-non-efi-boot.patch