linux-kernel - [PATCH 4.7 39/69] x86/efi: Only map RAM into EFI page tables if in mixed-mode

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Date:   Wed, 28 Sep 2016 11:05:21 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Waiman Long <waiman.long@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Theodore Tso <tytso@....edu>, Arnd Bergmann <arnd@...db.de>,
        Scott J Norton <scott.norton@....com>,
        Douglas Hatch <doug.hatch@....com>,
        Matt Fleming <matt@...eblueprint.co.uk>
Subject: [PATCH 4.7 39/69] x86/efi: Only map RAM into EFI page tables if in mixed-mode

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matt Fleming <matt@...eblueprint.co.uk>

commit 1297667083d5442aafe3e337b9413bf02b114edb upstream.

Waiman reported that booting with CONFIG_EFI_MIXED enabled on his
multi-terabyte HP machine results in boot crashes, because the EFI
region mapping functions loop forever while trying to map those
regions describing RAM.

While this patch doesn't fix the underlying hang, there's really no
reason to map EFI_CONVENTIONAL_MEMORY regions into the EFI page tables
when mixed-mode is not in use at runtime.

Reported-by: Waiman Long <waiman.long@....com>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Theodore Ts'o <tytso@....edu>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Scott J Norton <scott.norton@....com>
Cc: Douglas Hatch <doug.hatch@....com>
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/platform/efi/efi_64.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -244,7 +244,7 @@ int __init efi_setup_page_tables(unsigne
 	 * text and allocate a new stack because we can't rely on the
 	 * stack pointer being < 4GB.
 	 */
-	if (!IS_ENABLED(CONFIG_EFI_MIXED))
+	if (!IS_ENABLED(CONFIG_EFI_MIXED) || efi_is_native())
 		return 0;
 
 	/*