6.8-stable review patch. If anyone has any objections, please let me know.
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From: Pawan Gupta pawan.kumar.gupta@linux.intel.com
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@suse.com/ Fixes: baf8361e5455 ("x86/bugs: Add asm helpers for executing VERW") Reported-by: Nikolay Borisov nik.borisov@suse.com Signed-off-by: Pawan Gupta pawan.kumar.gupta@linux.intel.com Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Link: https://lore.kernel.org/all/20240226-verw-arg-fix-v1-1-7b37ee6fd57d%40linux.... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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__ */