[PATCH 2/6] s390: implement nospec_[load|ptr]

Martin Schwidefsky
2018-01-17T09:48:35Z

Implement nospec_load() and nospec_ptr() for s390 with the new
gmb() barrier between the boundary condition and the load that
may not be done speculatively.

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
arch/s390/include/asm/barrier.h | 38 ++++++++++++++++++++++++++++++++++++++
arch/s390/kernel/alternative.c | 7 +++++++
2 files changed, 45 insertions(+)

diff --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h
index 1043260..b8836a6 100644
--- a/arch/s390/include/asm/barrier.h
+++ b/arch/s390/include/asm/barrier.h
@@ -8,6 +8,8 @@
#ifndef __ASM_BARRIER_H
#define __ASM_BARRIER_H

+#include <asm/alternative.h>
+
/*
* Force strict CPU ordering.
* And yes, this is required on UP too when we're talking
@@ -23,6 +25,42 @@

#define mb() do { asm volatile(__ASM_BARRIER : : : "memory"); } while (0)

+static inline void gmb(void)
+{
+ asm volatile(
+ ALTERNATIVE("", ".long 0xb2e8f000", 81)
+ : : : "memory");
+}
+#define gmb gmb
+
+#define nospec_ptr(ptr, lo, hi) \
+({ \
+ typeof (ptr) __ptr = (ptr); \
+ typeof (ptr) __lo = (lo); \
+ typeof (ptr) __hi = (hi); \
+ typeof (ptr) __vptr = NULL; \
+ \
+ if (__lo <= __ptr && __ptr < __hi) { \
+ gmb(); \
+ __vptr = __ptr; \
+ } \
+ __vptr; \
+})
+
+#define nospec_load(ptr, lo, hi) \
+({ \
+ typeof (ptr) __ptr = (ptr); \
+ typeof (ptr) __lo = (lo); \
+ typeof (ptr) __hi = (hi); \
+ typeof (*ptr) __v = (typeof(*__ptr))(unsigned long) 0; \
+ \
+ if (__lo <= __ptr && __ptr < __hi) { \
+ gmb(); \
+ __v = *__ptr; \
+ } \
+ __v; \
+})
+
#define rmb() barrier()
#define wmb() barrier()
#define dma_rmb() mb()
diff --git a/arch/s390/kernel/alternative.c b/arch/s390/kernel/alternative.c
index 1abf4f3..33d2e88 100644
--- a/arch/s390/kernel/alternative.c
+++ b/arch/s390/kernel/alternative.c
@@ -15,6 +15,13 @@ static int __init disable_alternative_instructions(char *str)

early_param("noaltinstr", disable_alternative_instructions);

+static int __init nogmb_setup_early(char *str)
+{
+ __clear_facility(81, S390_lowcore.alt_stfle_fac_list);
+ return 0;
+}
+early_param("nogmb", nogmb_setup_early);
+
struct brcl_insn {
u16 opc;
s32 disp;
--
2.7.4