From: Mark Brown <broonie@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>, Will Deacon <will@kernel.org>,
linux-crypto@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Eric Biggers <ebiggers@google.com>
Subject: Re: [PATCH 0/3] arm64: Open code .arch_extension
Date: Thu, 23 Apr 2020 12:18:03 +0100 [thread overview]
Message-ID: <20200423111803.GG4808@sirena.org.uk> (raw)
In-Reply-To: <20200422180027.GH3585@gaia>
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On Wed, Apr 22, 2020 at 07:00:28PM +0100, Catalin Marinas wrote:
> On Wed, Mar 25, 2020 at 11:50:38AM +0000, Mark Brown wrote:
> > Since BTI is a mandatory feature of v8.5 there is no BTI arch_extension,
> > you can only enable it by moving the base architecture to v8.5. You'd
> > need to use .arch and that feels likely to find us sharp edges to run
> > into.
> For MTE, .arch armv8-a+memtag won't work since this is only available
> with armv8.5-a. My preference would be to have the highest arch version
> supported by the kernel in the assembler.h file, i.e. ".arch armv8.5-a"
> followed by .arch_extension in each .S file, as needed.
I think we decided that .arch_extension was too new to be used for
things like the crypto stuff where we still support older toolchains?
> Forcing .S files to armv8.5 would not cause any problems with
> the base armv8.0 that the kernel image support since it shouldn't change
> the opcodes gas generates. The .S files would use alternatives anyway
> (or simply have code not called).
We do loose the checking that the assembler does that nobody used a
newer feature by mistake but yeah, shouldn't affect the output.
> The inline asm is slightly more problematic, especially with the clang
> builtin assembler which goes in a single pass. But we could do something
> similar to what we did with the LSE atomics and raising the base of the
> inline asm to armv8.5 (or 8.6 etc., whatever we need in the future).
FWIW I did something different to this for BTI so I wasn't using the
instructions directly so I was going to abandon this series.
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next prev parent reply other threads:[~2020-04-23 11:18 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-25 11:41 [PATCH 0/3] arm64: Open code .arch_extension Mark Brown
2020-03-25 11:41 ` [PATCH 1/3] arm64: asm: Provide macro to control enabling architecture extensions Mark Brown
2020-03-25 11:41 ` [PATCH 2/3] arm64: lib: Use ARM64_EXTENSIONS() Mark Brown
2020-03-25 11:41 ` [PATCH 3/3] arm64: crypto: " Mark Brown
2020-03-25 11:45 ` [PATCH 0/3] arm64: Open code .arch_extension Ard Biesheuvel
2020-03-25 11:50 ` Mark Brown
2020-03-25 11:54 ` Ard Biesheuvel
2020-03-25 12:01 ` Mark Brown
2020-03-25 12:03 ` Mark Rutland
2020-03-25 12:24 ` Robin Murphy
2020-04-22 18:00 ` Catalin Marinas
2020-04-23 11:18 ` Mark Brown [this message]
2020-04-23 11:59 ` Catalin Marinas
2020-04-23 13:40 ` Catalin Marinas
2020-03-25 12:31 ` Mark Rutland
2020-03-25 13:26 ` Ard Biesheuvel
2020-03-25 13:30 ` Mark Brown
2020-03-25 13:27 ` Mark Brown
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