linux-kernel - Re: [PATCH 3/8] arm64: cpufeature: Add CPU capability for AArch32 EL1 support

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Message-ID: <1b76993491176577567a0960a435dac0@kernel.org>
Date:   Wed, 15 Apr 2020 09:55:57 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Will Deacon <will@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mark Rutland <mark.rutland@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Doug Anderson <dianders@...omium.org>, kernel-team@...roid.com
Subject: Re: [PATCH 3/8] arm64: cpufeature: Add CPU capability for AArch32 EL1
 support

Hi Will,

On 2020-04-14 22:31, Will Deacon wrote:
> Although we emit a "SANITY CHECK" warning and taint the kernel if we
> detect a CPU mismatch for AArch32 support at EL1, we still online the
> CPU with disastrous consequences for any running 32-bit VMs.
> 
> Introduce a capability for AArch32 support at EL1 so that late onlining
> of incompatible CPUs is forbidden.
> 
> Signed-off-by: Will Deacon <will@...nel.org>

Definitely an improvement over the current situation, as the direct read
of ID_AA64PFR0 was always a bit dodgy. Given that I'm pretty sure these 
new
braindead SoCs are going to run an older version of the kernel, should 
we
Cc stable for this?

Otherwise:

Acked-by: Marc Zyngier <maz@...nel.org>

         M.
-- 
Jazz is not dead. It just smells funny...