From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Sami Tolvanen <samitolvanen@google.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Kees Cook <keescook@chromium.org>,
Catalin Marinas <catalin.marinas@arm.com>,
LKML <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Andrew Murray <andrew.murray@arm.com>,
Will Deacon <will@kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] arm64: lse: fix LSE atomics with LLVM's integrated assembler
Date: Tue, 8 Oct 2019 23:03:24 +0200 [thread overview]
Message-ID: <CAKv+Gu82ERZjaEH265+RNVjtQSk51ekHONniDZg-4vWy1VHkuQ@mail.gmail.com> (raw)
In-Reply-To: <c0f0eb7e-9e46-10cc-1277-b37fcd48d0be@arm.com>
On Tue, 8 Oct 2019 at 18:19, Robin Murphy <robin.murphy@arm.com> wrote:
>
> On 08/10/2019 16:22, Sami Tolvanen wrote:
> > On Mon, Oct 7, 2019 at 2:46 PM 'Nick Desaulniers' via Clang Built
> > Linux <clang-built-linux@googlegroups.com> wrote:
> >> I'm worried that one of these might lower to LSE atomics without
> >> ALTERNATIVE guards by blanketing all C code with `-march=armv8-a+lse`.
> >
> > True, that's a valid concern. I think adding the directive to each
> > assembly block is the way forward then, assuming the maintainers are
> > fine with that.
>
> It's definitely a valid concern in principle, but in practice note that
> lse.h ends up included in ~99% of C files, so the extension is enabled
> more or less everywhere already.
>
lse.h currently does
__asm__(".arch_extension lse");
which instructs the assembler to permit the use of LSE opcodes, but it
does not instruct the compiler to emit them, so this is not quite the
same thing.
next prev parent reply other threads:[~2019-10-08 21:03 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-07 20:14 [PATCH] arm64: lse: fix LSE atomics with LLVM's integrated assembler Sami Tolvanen
2019-10-07 20:28 ` Nick Desaulniers
2019-10-07 21:24 ` Sami Tolvanen
2019-10-07 21:46 ` Nick Desaulniers
2019-10-08 15:22 ` Sami Tolvanen
2019-10-08 16:18 ` Robin Murphy
2019-10-08 21:03 ` Ard Biesheuvel [this message]
2019-10-09 10:03 ` Robin Murphy
2019-10-08 8:37 ` Andrew Murray
2019-10-08 21:27 ` [PATCH v2] " Sami Tolvanen
2019-10-08 22:15 ` Nick Desaulniers
2019-10-08 23:31 ` Andrew Murray
2019-10-08 23:59 ` Sami Tolvanen
2019-10-09 0:01 ` Nathan Chancellor
2019-10-09 8:29 ` Andrew Murray
2019-10-10 20:59 ` Kees Cook
2019-10-15 0:33 ` Will Deacon
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