arm64: barrier: Add CSDB macros to control data-value prediction

From: Will Deacon <will.deacon@arm.com>

commit 669474e772b952b14f4de4845a1558fd4c0414a4 upstream.

For CPUs capable of data value prediction, CSDB waits for any outstanding
predictions to architecturally resolve before allowing speculative execution
to continue. Provide macros to expose it to the arch code.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com [v4.9 backport]
Tested-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 7193bf9..b223b1b 100644 (file)
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -87,6 +87,13 @@
        .endm
 
 /*
+ * Value prediction barrier
+ */
+       .macro  csdb
+       hint    #20
+       .endm
+
+/*
  * NOP sequence
  */
        .macro  nops, num

diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 0fe7e43..c68fdc5 100644 (file)
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -31,6 +31,8 @@
 #define dmb(opt)       asm volatile("dmb " #opt : : : "memory")
 #define dsb(opt)       asm volatile("dsb " #opt : : : "memory")
 
+#define csdb()         asm volatile("hint #20" : : : "memory")
+
 #define mb()           dsb(sy)
 #define rmb()          dsb(ld)
 #define wmb()          dsb(st)