netdev - [RFC PATCH net-next 1/4] arm64: barrier: add DGH macros to control memory accesses merging

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Message-ID: <1627020969-32945-2-git-send-email-huangguangbin2@huawei.com>
Date:   Fri, 23 Jul 2021 14:16:06 +0800
From:   Guangbin Huang <huangguangbin2@...wei.com>
To:     <davem@...emloft.net>, <kuba@...nel.org>,
        <catalin.marinas@....com>, <will@...nel.org>, <maz@...nel.org>,
        <mark.rutland@....com>, <dbrazdil@...gle.com>, <qperret@...gle.com>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <lipeng321@...wei.com>,
        <huangguangbin2@...wei.com>
Subject: [RFC PATCH net-next 1/4] arm64: barrier: add DGH macros to control memory accesses merging

From: Xiongfeng Wang <wangxiongfeng2@...wei.com>

DGH prohibits merging memory accesses with Normal-NC or Device-GRE
attributes before the hint instruction with any memory accesses
appearing after the hint instruction. Provide macros to expose it to the
arch code.

Signed-off-by: Xiongfeng Wang <wangxiongfeng2@...wei.com>
Signed-off-by: Cheng Jian <cj.chengjian@...wei.com>
Signed-off-by: Yufeng Mo <moyufeng@...wei.com>
---
 arch/arm64/include/asm/assembler.h | 7 +++++++
 arch/arm64/include/asm/barrier.h   | 1 +
 2 files changed, 8 insertions(+)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 89faca0e740d..5a3348b5e9f3 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -90,6 +90,13 @@
 	.endm
 
 /*
+ * Data gathering hint
+ */
+	.macro	dgh
+	hint	#6
+	.endm
+
+/*
  * RAS Error Synchronization barrier
  */
 	.macro  esb
diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 451e11e5fd23..02e1735706d2 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -22,6 +22,7 @@
 #define dmb(opt)	asm volatile("dmb " #opt : : : "memory")
 #define dsb(opt)	asm volatile("dsb " #opt : : : "memory")
 
+#define dgh()		asm volatile("hint #6" : : : "memory")
 #define psb_csync()	asm volatile("hint #17" : : : "memory")
 #define tsb_csync()	asm volatile("hint #18" : : : "memory")
 #define csdb()		asm volatile("hint #20" : : : "memory")
-- 
2.8.1