From: James Morse Date: Tue, 18 Jun 2019 15:17:33 +0000 (+0100) Subject: arm64: assembler: Switch ESB-instruction with a vanilla nop if !ARM64_HAS_RAS X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=2b68a2a963a157f024c67c0697b16f5f792c8a35;p=openwrt%2Fstaging%2Fblogic.git arm64: assembler: Switch ESB-instruction with a vanilla nop if !ARM64_HAS_RAS 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 --- 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 /*