From a9e2959cc4e9ac216e5392c3ee3b4bc7c35f4c88 Mon Sep 17 00:00:00 2001 From: James Morse Date: Wed, 31 Jul 2019 17:13:23 +0800 Subject: [PATCH] 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 Signed-off-by: James Morse Signed-off-by: Marc Zyngier Signed-off-by: Sasha Levin Signed-off-by: Yang Yingliang --- 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 570d28d9863f..becb5454151e 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -104,7 +104,11 @@ * RAS Error Synchronization barrier */ .macro esb +#ifdef CONFIG_ARM64_RAS_EXTN hint #16 +#else + nop +#endif .endm /* -- GitLab