This is a note to let you know that I've just added the patch titled
x86/bugs: Use fixed addressing for VERW operand
to the 6.8-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-bugs-use-fixed-addressing-for-verw-operand.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8009479ee919b9a91674f48050ccbff64eafedaa Mon Sep 17 00:00:00 2001
From: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Date: Mon, 26 Feb 2024 15:52:33 -0800
Subject: x86/bugs: Use fixed addressing for VERW operand
From: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
commit 8009479ee919b9a91674f48050ccbff64eafedaa upstream.
The macro used for MDS mitigation executes VERW with relative
addressing for the operand. This was necessary in earlier versions of
the series. Now it is unnecessary and creates a problem for backports
on older kernels that don't support relocations in alternatives.
Relocation support was added by commit 270a69c4485d ("x86/alternative:
Support relocations in alternatives"). Also asm for fixed addressing
is much cleaner than relative RIP addressing.
Simplify the asm by using fixed addressing for VERW operand.
[ dhansen: tweak changelog ]
Closes: https://lore.kernel.org/lkml/20558f89-299b-472e-9a96-171403a83bd6@xxxxxxxx/
Fixes: baf8361e5455 ("x86/bugs: Add asm helpers for executing VERW")
Reported-by: Nikolay Borisov <nik.borisov@xxxxxxxx>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/20240226-verw-arg-fix-v1-1-7b37ee6fd57d%40linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/nospec-branch.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -332,7 +332,7 @@
* Note: Only the memory operand variant of VERW clears the CPU buffers.
*/
.macro CLEAR_CPU_BUFFERS
- ALTERNATIVE "", __stringify(verw _ASM_RIP(mds_verw_sel)), X86_FEATURE_CLEAR_CPU_BUF
+ ALTERNATIVE "", __stringify(verw mds_verw_sel), X86_FEATURE_CLEAR_CPU_BUF
.endm
#else /* __ASSEMBLY__ */
Patches currently in stable-queue which might be from pawan.kumar.gupta@xxxxxxxxxxxxxxx are
queue-6.8/x86-bugs-use-fixed-addressing-for-verw-operand.patch
