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Message-Id: <20190729190758.376366301@linuxfoundation.org>
Date: Mon, 29 Jul 2019 21:21:48 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Julien Thierry <julien.thierry@....com>,
James Morse <james.morse@....com>,
Marc Zyngier <marc.zyngier@....com>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.2 112/215] arm64: assembler: Switch ESB-instruction with a vanilla nop if !ARM64_HAS_RAS
[ Upstream commit 2b68a2a963a157f024c67c0697b16f5f792c8a35 ]
The ESB-instruction is a nop on CPUs that don't implement the RAS
extensions. This lets us use it in places like the vectors without
having to use alternatives.
If someone disables CONFIG_ARM64_RAS_EXTN, this instruction still has
its RAS extensions behaviour, but we no longer read DISR_EL1 as this
register does depend on alternatives.
This could go wrong if we want to synchronize an SError from a KVM
guest. On a CPU that has the RAS extensions, but the KConfig option
was disabled, we consume the pending SError with no chance of ever
reading it.
Hide the ESB-instruction behind the CONFIG_ARM64_RAS_EXTN option,
outputting a regular nop if the feature has been disabled.
Reported-by: Julien Thierry <julien.thierry@....com>
Signed-off-by: James Morse <james.morse@....com>
Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
arch/arm64/include/asm/assembler.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 570d195a184d..e3a15c751b13 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -96,7 +96,11 @@
* RAS Error Synchronization barrier
*/
.macro esb
+#ifdef CONFIG_ARM64_RAS_EXTN
hint #16
+#else
+ nop
+#endif
.endm
/*
--
2.20.1
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