This is a note to let you know that I've just added the patch titled
x86/kexec: Make kexec (mostly) work in 5-level paging mode
to the 4.15-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:
x86-kexec-make-kexec-mostly-work-in-5-level-paging-mode.patch
and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5bf30316991d5bcda046343ee77d823cf16fdd03 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Date: Mon, 29 Jan 2018 14:08:45 +0300
Subject: x86/kexec: Make kexec (mostly) work in 5-level paging mode
From: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
commit 5bf30316991d5bcda046343ee77d823cf16fdd03 upstream.
Currently kexec() will crash when switching into a 5-level paging
enabled kernel.
I missed that we need to change relocate_kernel() to set CR4.LA57
flag if the kernel has 5-level paging enabled.
I avoided using #ifdef CONFIG_X86_5LEVEL here and inferred if we need to
enable 5-level paging from previous CR4 value. This way the code is
ready for boot-time switching between paging modes.
With this patch applied, in addition to kexec 4-to-4 which always worked,
we can kexec 4-to-5 and 5-to-5 - while 5-to-4 will need more work.
Reported-by: Baoquan He <bhe@xxxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Tested-by: Baoquan He <bhe@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.14+
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Fixes: 77ef56e4f0fb ("x86: Enable 5-level paging support via CONFIG_X86_5LEVEL=y")
Link: http://lkml.kernel.org/r/20180129110845.26633-1-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/relocate_kernel_64.S | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -68,6 +68,9 @@ relocate_kernel:
movq %cr4, %rax
movq %rax, CR4(%r11)
+ /* Save CR4. Required to enable the right paging mode later. */
+ movq %rax, %r13
+
/* zero out flags, and disable interrupts */
pushq $0
popfq
@@ -126,8 +129,13 @@ identity_mapped:
/*
* Set cr4 to a known state:
* - physical address extension enabled
+ * - 5-level paging, if it was enabled before
*/
movl $X86_CR4_PAE, %eax
+ testq $X86_CR4_LA57, %r13
+ jz 1f
+ orl $X86_CR4_LA57, %eax
+1:
movq %rax, %cr4
jmp 1f
Patches currently in stable-queue which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
queue-4.15/x86-kexec-make-kexec-mostly-work-in-5-level-paging-mode.patch