[PATCH 2/6] arm64: fix "dc cvau" cache operation on errata-affected core

From: Andre Przywara
Date: Mon May 09 2016 - 12:49:36 EST


The ARM errata 819472, 826319, 827319 and 824069 for affected
Cortex-A53 cores demand to promote "dc cvau" instructions to
"dc civac" as well.
Attribute the usage of the instruction in __flush_cache_user_range
to also be covered by our alternative patching efforts.
For that we introduce an assembly macro which both deals with
alternatives while still tagging the instructions as USER.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
arch/arm64/include/asm/alternative.h | 4 ++++
arch/arm64/mm/cache.S | 2 +-
2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
index 502c9ef..d4a69a9 100644
--- a/arch/arm64/include/asm/alternative.h
+++ b/arch/arm64/include/asm/alternative.h
@@ -151,6 +151,10 @@ void apply_alternatives(void *start, size_t length);
#define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \
alternative_insn insn1, insn2, cap, IS_ENABLED(cfg)

+.macro user_alt, label, oldinstr, newinstr, cond
+9999: alternative_insn "\oldinstr", "\newinstr", \cond
+ _ASM_EXTABLE 9999b, \label
+.endm

/*
* Generate the assembly for UAO alternatives with exception table entries.
diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S
index 6df0706..82f40bd 100644
--- a/arch/arm64/mm/cache.S
+++ b/arch/arm64/mm/cache.S
@@ -54,7 +54,7 @@ ENTRY(__flush_cache_user_range)
sub x3, x2, #1
bic x4, x0, x3
1:
-USER(9f, dc cvau, x4 ) // clean D line to PoU
+user_alt 9f, "dc cvau, x4", "dc civac, x4", ARM64_WORKAROUND_CLEAN_CACHE
add x4, x4, x2
cmp x4, x1
b.lo 1b
--
2.7.3