From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH v1 1/3] arm64: add a macro for SError synchronization Date: Wed, 1 Nov 2017 11:24:59 +0000 Message-ID: <6dc82768-8564-a54e-041b-3b9965fa038b@arm.com> References: <1509563697-6359-1-git-send-email-gengdongjiu@huawei.com> <1509563697-6359-2-git-send-email-gengdongjiu@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1509563697-6359-2-git-send-email-gengdongjiu@huawei.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Dongjiu Geng , catalin.marinas@arm.com, will.deacon@arm.com, marc.zyngier@arm.com, christoffer.dall@linaro.org, james.morse@arm.com, mark.rutland@arm.com, ard.biesheuvel@linaro.org, cov@codeaurora.org, Dave.Martin@arm.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu List-Id: kvmarm@lists.cs.columbia.edu On 01/11/17 19:14, Dongjiu Geng wrote: > ARMv8.2 adds a control bit to each SCTLR_ELx to insert implicit > Error Synchronization Barrier(IESB) operations at exception handler entry > and exit. But not all hardware platform which support RAS Extension > can support IESB. So for this case, software needs to manually insert > Error Synchronization Barrier(ESB) operations. > > In this macros, if system supports RAS Extensdddon instead of IESB, > it will insert an ESB instruction. > > Signed-off-by: Dongjiu Geng > --- > arch/arm64/include/asm/assembler.h | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h > index d4c0adf..e6c79c4 100644 > --- a/arch/arm64/include/asm/assembler.h > +++ b/arch/arm64/include/asm/assembler.h > @@ -517,4 +517,13 @@ > #endif > .endm > > + .macro error_synchronize > +alternative_if ARM64_HAS_IESB > + b 1f > +alternative_else_nop_endif > +alternative_if ARM64_HAS_RAS_EXTN > + esb > +alternative_else_nop_endif > +1: > + .endm Having a branch in here is pretty horrible, and furthermore using label number 1 has a pretty high chance of subtly breaking code where this macro is inserted. Can we not somehow nest or combine the alternative conditions here? Robin. > #endif /* __ASM_ASSEMBLER_H */ >