lkml.org 
[lkml]   [2019]   [Jul]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH AUTOSEL 4.19 064/101] arm64: assembler: Switch ESB-instruction with a vanilla nop if !ARM64_HAS_RAS
Date
From: James Morse <james.morse@arm.com>

[ 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@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.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 f90f5d83b228..5a97ac853168 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -112,7 +112,11 @@
* RAS Error Synchronization barrier
*/
.macro esb
+#ifdef CONFIG_ARM64_RAS_EXTN
hint #16
+#else
+ nop
+#endif
.endm

/*
--
2.20.1
\
 
 \ /
  Last update: 2019-07-19 06:10    [W:2.159 / U:0.600 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site