[PATCH 4.9 24/66] arm64: Move post_ttbr_update_workaround to C code

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mark Rutland <mark.rutland@xxxxxxx>


From: Marc Zyngier <marc.zyngier@xxxxxxx>

commit 95e3de3590e3f2358bb13f013911bc1bfa5d3f53 upstream.

We will soon need to invoke a CPU-specific function pointer after changing
page tables, so move post_ttbr_update_workaround out into C code to make
this possible.

Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx> [v4.9 backport]
Tested-by: Greg Hackmann <ghackmann@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/arm64/include/asm/assembler.h |   13 -------------
 arch/arm64/mm/context.c            |    9 +++++++++
 arch/arm64/mm/proc.S               |    3 +--
 3 files changed, 10 insertions(+), 15 deletions(-)

--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -435,17 +435,4 @@ alternative_endif
 	and	\phys, \pte, #(((1 << (48 - PAGE_SHIFT)) - 1) << PAGE_SHIFT)
 	.endm
 
-/*
- * Errata workaround post TTBR0_EL1 update.
- */
-	.macro	post_ttbr0_update_workaround
-#ifdef CONFIG_CAVIUM_ERRATUM_27456
-alternative_if ARM64_WORKAROUND_CAVIUM_27456
-	ic	iallu
-	dsb	nsh
-	isb
-alternative_else_nop_endif
-#endif
-	.endm
-
 #endif	/* __ASM_ASSEMBLER_H */
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -233,6 +233,15 @@ switch_mm_fastpath:
 	cpu_switch_mm(mm->pgd, mm);
 }
 
+/* Errata workaround post TTBRx_EL1 update. */
+asmlinkage void post_ttbr_update_workaround(void)
+{
+	asm(ALTERNATIVE("nop; nop; nop",
+			"ic iallu; dsb nsh; isb",
+			ARM64_WORKAROUND_CAVIUM_27456,
+			CONFIG_CAVIUM_ERRATUM_27456));
+}
+
 static int asids_init(void)
 {
 	asid_bits = get_cpu_asid_bits();
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -139,8 +139,7 @@ ENTRY(cpu_do_switch_mm)
 	isb
 	msr	ttbr0_el1, x0			// now update TTBR0
 	isb
-	post_ttbr0_update_workaround
-	ret
+	b	post_ttbr_update_workaround	// Back to C code...
 ENDPROC(cpu_do_switch_mm)
 
 	.pushsection ".idmap.text", "awx"