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

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Date:   Tue, 8 Nov 2022 14:56:57 +0000
From:   Will Deacon <will@...nel.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Ard Biesheuvel <ardb@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Eric Biggers <ebiggers@...nel.org>,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        Kees Cook <keescook@...omium.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Adam Langley <agl@...gle.com>
Subject: Re: [PATCH v2] arm64: Enable data independent timing (DIT) in the
 kernel

On Tue, Nov 08, 2022 at 02:41:26PM +0000, Mark Rutland wrote:
> On Mon, Nov 07, 2022 at 06:24:00PM +0100, Ard Biesheuvel wrote:
> > diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
> > index 8b02d310838f9240..3032a82ea51a19f7 100644
> > --- a/arch/arm64/kernel/suspend.c
> > +++ b/arch/arm64/kernel/suspend.c
> > @@ -60,6 +60,8 @@ void notrace __cpu_suspend_exit(void)
> >  	 * PSTATE was not saved over suspend/resume, re-enable any detected
> >  	 * features that might not have been set correctly.
> >  	 */
> > +	if (cpu_has_dit())
> > +		set_pstate_dit(1);
> 
> As above, I'd prefer if we either renamed cpu_has_dit() to cpus_have_dit(), or
> just open-coded this as:
> 
> 	if (cpus_have_const_cap(ARM64_HAS_DIT))
> 		set_pstate_dit(1);
> 
> With either of those options:
> 
>   Acked-by: Mark Rutland <mark.rutland@....com>
> 
> I assume Will might fix that up when applying.

Yup, I'll take care of that.

Will