linux-kernel - [RFC PATCH for 4.16 10/11] membarrier: arm64: Provide core serializing command

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Date:   Fri, 22 Dec 2017 15:15:35 -0500
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Will Deacon <will.deacon@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Boqun Feng <boqun.feng@...il.com>,
        Andrew Hunter <ahh@...gle.com>,
        Maged Michael <maged.michael@...il.com>,
        Avi Kivity <avi@...lladb.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Dave Watson <davejwatson@...com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andrea Parri <parri.andrea@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Greg Hackmann <ghackmann@...gle.com>,
        David Sehr <sehr@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        linux-arch@...r.kernel.org
Subject: [RFC PATCH for 4.16 10/11] membarrier: arm64: Provide core serializing command

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Andy Lutomirski <luto@...nel.org>
CC: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
CC: Boqun Feng <boqun.feng@...il.com>
CC: Andrew Hunter <ahh@...gle.com>
CC: Maged Michael <maged.michael@...il.com>
CC: Avi Kivity <avi@...lladb.com>
CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC: Paul Mackerras <paulus@...ba.org>
CC: Michael Ellerman <mpe@...erman.id.au>
CC: Dave Watson <davejwatson@...com>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Ingo Molnar <mingo@...hat.com>
CC: "H. Peter Anvin" <hpa@...or.com>
CC: Andrea Parri <parri.andrea@...il.com>
CC: Russell King <linux@...linux.org.uk>
CC: Greg Hackmann <ghackmann@...gle.com>
CC: Will Deacon <will.deacon@....com>
CC: David Sehr <sehr@...gle.com>
CC: x86@...nel.org
CC: linux-arch@...r.kernel.org
---
 arch/arm64/Kconfig        | 1 +
 arch/arm64/kernel/entry.S | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index c9a7e9e1414f..5b0c06d8dbbe 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -16,6 +16,7 @@ config ARM64
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
 	select ARCH_HAS_KCOV
+	select ARCH_HAS_MEMBARRIER_SYNC_CORE
 	select ARCH_HAS_SET_MEMORY
 	select ARCH_HAS_SG_CHAIN
 	select ARCH_HAS_STRICT_KERNEL_RWX
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 6d14b8f29b5f..5edde1c2e93e 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -302,6 +302,10 @@ alternative_else_nop_endif
 	ldp	x28, x29, [sp, #16 * 14]
 	ldr	lr, [sp, #S_LR]
 	add	sp, sp, #S_FRAME_SIZE		// restore sp
+	/*
+	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on eret context synchronization
+	 * when returning from IPI handler, and when returning to user-space.
+	 */
 	eret					// return to kernel
 	.endm
 
-- 
2.11.0