<snip>
+
+.pushsection .entry.text, "ax"
+
+.align L1_CACHE_BYTES, 0xcc
+SYM_CODE_START_NOALIGN(mds_verw_sel)
+ UNWIND_HINT_UNDEFINED
+ ANNOTATE_NOENDBR
+ .word __KERNEL_DS
+SYM_CODE_END(mds_verw_sel);
+/* For KVM */
+EXPORT_SYMBOL_GPL(mds_verw_sel);
+
+.popsection
<snip>
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index c55cc243592e..005e69f93115 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -329,6 +329,21 @@
#endif
.endm
+/*
+ * Macros to execute VERW instruction that mitigate transient data sampling
+ * attacks such as MDS. On affected systems a microcode update overloaded VERW
+ * instruction to also clear the CPU buffers. VERW clobbers CFLAGS.ZF.
+ *
+ * Note: Only the memory operand variant of VERW clears the CPU buffers.
+ */
+.macro EXEC_VERW
+ verw _ASM_RIP(mds_verw_sel)
+.endm
+
+.macro CLEAR_CPU_BUFFERS
+ ALTERNATIVE "", __stringify(EXEC_VERW), X86_FEATURE_CLEAR_CPU_BUF
+.endm
What happened with the first 5 bytes of a 7 byte nop being complemented
by __KERNEL_DS in order to handle VERW being executed after user
registers are restored and having its memory operand ?
+
#else /* __ASSEMBLY__ */
#define ANNOTATE_RETPOLINE_SAFE \
