linux-kernel - Re: [PATCH v4 0/4] Upgrade READ_ONCE() to RCpc acquire on arm64 with LTO

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Date:   Mon, 9 Nov 2020 23:25:51 +0000
From:   Will Deacon <will@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 0/4] Upgrade READ_ONCE() to RCpc acquire on arm64 with
 LTO

On Tue, Nov 03, 2020 at 12:17:17PM +0000, Will Deacon wrote:
> Hi all,
> 
> These patches were previously posted as part of a larger series enabling
> architectures to override __READ_ONCE():
> 
>   v3: https://lore.kernel.org/lkml/20200710165203.31284-1-will@kernel.org/
> 
> With the bulk of that merged, the four patches here override READ_ONCE()
> so that it gains RCpc acquire semantics on arm64 when LTO is enabled. We
> can revisit this as and when the compiler provides a means for us to reason
> about the result of dependency-breaking optimisations. In the meantime,
> this unblocks LTO for arm64, which I would really like to see merged so
> that we can focus on enabling CFI.
> 
> I plan to queue these on their own branch in the arm64 tree for 5.11 at
> -rc3.

Now pushed to for-next/lto:

https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-next/lto

with Mark's comments addressed.

Will