From: Catalin Marinas <catalin.marinas@arm.com>
To: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH] arm64: Don't allow SVE to be used with BROKEN_GAS_INST
Date: Wed, 2 Mar 2022 13:58:13 +0000 [thread overview]
Message-ID: <Yh939U9dn7fvhKPz@arm.com> (raw)
In-Reply-To: <20220225184045.5502-1-broonie@kernel.org>
On Fri, Feb 25, 2022 at 06:40:45PM +0000, Mark Brown wrote:
> We support building the kernel with archaic versions of binutils which
> had some confusion regarding how instructions should be encoded for .inst
> which we work around with the __emit_inst() macro. Unfortunately we have
> not consistently used this macro, one of the places where it's missed being
> the macros that manually encode SVE instructions. This means that kernels
> built with such toolchains have never supported SVE correctly.
>
> Since these toolchains are very old (some idle research suggested 2015
> era) it seems more sensible to just refuse to build SVE support with them,
> in the unlikely event that someone has a need to use such a toolchain to
> build a kernel which will run on a system with SVE support they can always
> fix this properly but it seems more likely that we will deprecate support
> for these toolchains and remove __emit_inst() before that happens.
>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
> arch/arm64/Kconfig | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index f8e5f64fc40b..4312cc622277 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1899,6 +1899,7 @@ endmenu
> config ARM64_SVE
> bool "ARM Scalable Vector Extension support"
> default y
> + depends on !BROKEN_GAS_INST
It looks like it's not just SVE affected here. A grep for "\.inst\>"
shows a few places in the crypto code as well. How hard is it to use
__emit_inst() in these places?
--
Catalin
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next prev parent reply other threads:[~2022-03-02 13:59 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-25 18:40 [PATCH] arm64: Don't allow SVE to be used with BROKEN_GAS_INST Mark Brown
2022-03-02 13:58 ` Catalin Marinas [this message]
2022-03-02 16:04 ` Mark Brown
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