linux-kernel - [PATCH 5.4 112/434] MIPS: syscall: Emit Loongson3 sync workarounds within asm

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Date:   Sun, 29 Dec 2019 18:22:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Paul Burton <paul.burton@...s.com>,
        linux-mips@...r.kernel.org, Huacai Chen <chenhc@...ote.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 112/434] MIPS: syscall: Emit Loongson3 sync workarounds within asm

From: Paul Burton <paul.burton@...s.com>

[ Upstream commit e84957e6ae043bb83ad6ae7e949a1ce97b6bbfef ]

Generate the sync instructions required to workaround Loongson3 LL/SC
errata within inline asm blocks, which feels a little safer than doing
it from C where strictly speaking the compiler would be well within its
rights to insert a memory access between the separate asm statements we
previously had, containing sync & ll instructions respectively.

Signed-off-by: Paul Burton <paul.burton@...s.com>
Cc: linux-mips@...r.kernel.org
Cc: Huacai Chen <chenhc@...ote.com>
Cc: Jiaxun Yang <jiaxun.yang@...goat.com>
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/mips/kernel/syscall.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kernel/syscall.c b/arch/mips/kernel/syscall.c
index 3f16f3823031..c333e5788664 100644
--- a/arch/mips/kernel/syscall.c
+++ b/arch/mips/kernel/syscall.c
@@ -37,6 +37,7 @@
 #include <asm/signal.h>
 #include <asm/sim.h>
 #include <asm/shmparam.h>
+#include <asm/sync.h>
 #include <asm/sysmips.h>
 #include <asm/switch_to.h>
 
@@ -133,12 +134,12 @@ static inline int mips_atomic_set(unsigned long addr, unsigned long new)
 		  [efault] "i" (-EFAULT)
 		: "memory");
 	} else if (cpu_has_llsc) {
-		loongson_llsc_mb();
 		__asm__ __volatile__ (
 		"	.set	push					\n"
 		"	.set	"MIPS_ISA_ARCH_LEVEL"			\n"
 		"	li	%[err], 0				\n"
 		"1:							\n"
+		"	" __SYNC(full, loongson3_war) "			\n"
 		user_ll("%[old]", "(%[addr])")
 		"	move	%[tmp], %[new]				\n"
 		"2:							\n"
-- 
2.20.1