linux-kernel - Re: [PATCH v2] arm64: Enable data independent timing (DIT) in the kernel

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Date:   Tue,  8 Nov 2022 17:38:39 +0000
From:   Will Deacon <will@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org,
        Ard Biesheuvel <ardb@...nel.org>
Cc:     catalin.marinas@....com, kernel-team@...roid.com,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Eric Biggers <ebiggers@...nel.org>,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        Adam Langley <agl@...gle.com>, Marc Zyngier <maz@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arm64: Enable data independent timing (DIT) in the kernel

On Mon, 7 Nov 2022 18:24:00 +0100, Ard Biesheuvel wrote:
> The ARM architecture revision v8.4 introduces a data independent timing
> control (DIT) which can be set at any exception level, and instructs the
> CPU to avoid optimizations that may result in a correlation between the
> execution time of certain instructions and the value of the data they
> operate on.
> 
> The DIT bit is part of PSTATE, and is therefore context switched as
> usual, given that it becomes part of the saved program state (SPSR) when
> taking an exception. We have also defined a hwcap for DIT, and so user
> space can discover already whether or nor DIT is available. This means
> that, as far as user space is concerned, DIT is wired up and fully
> functional.
> 
> [...]

Applied to arm64 (for-next/cpufeature), thanks!

[1/1] arm64: Enable data independent timing (DIT) in the kernel
      https://git.kernel.org/arm64/c/01ab991fc0ee 

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev