linux-kernel - Re: [PATCH v3 2/3] arm64: enable tlbi range instructions

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Date:   Wed, 15 Jul 2020 13:10:23 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Zhenyu Ye <yezhenyu2@...wei.com>
Cc:     will@...nel.org, suzuki.poulose@....com, maz@...nel.org,
        steven.price@....com, guohanjun@...wei.com, olof@...om.net,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org, arm@...nel.org,
        xiexiangyou@...wei.com, prime.zeng@...ilicon.com,
        zhangshaokun@...ilicon.com, kuhn.chenqun@...wei.com
Subject: Re: [PATCH v3 2/3] arm64: enable tlbi range instructions

On Wed, Jul 15, 2020 at 03:19:44PM +0800, Zhenyu Ye wrote:
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index a0d94d063fa8..4e823b97c92e 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -82,11 +82,18 @@ endif
>  # compiler to generate them and consequently to break the single image contract
>  # we pass it only to the assembler. This option is utilized only in case of non
>  # integrated assemblers.
> +ifneq ($(CONFIG_AS_HAS_ARMV8_4), y)
>  branch-prot-flags-$(CONFIG_AS_HAS_PAC) += -Wa,-march=armv8.3-a
>  endif
> +endif

I couldn't find a clear statement in the gas documentation on what
happens if multiple -march options are passed. I think it's safer to
avoid this here.

>  KBUILD_CFLAGS += $(branch-prot-flags-y)
>  
> +ifeq ($(CONFIG_AS_HAS_ARMV8_4), y)
> +# make sure to pass the newest target architecture to -march.
> +KBUILD_CFLAGS	+= -Wa,-march=armv8.4-a
> +endif

I have a suspicion both of these options will break the LLVM integrated
assembler but we don't officially support it on arm64 yet (-Wa, doesn't
seem to get passed to the integrated asm).

Thanks for the re-spin.

-- 
Catalin