linux-kernel - Re: [PATCH v5] arm64: Add workaround for Fujitsu A64FX erratum 010001

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Message-ID: <20190228171506.GC226495@arrakis.emea.arm.com>
Date:   Thu, 28 Feb 2019 17:15:07 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     James Morse <james.morse@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will.deacon@....com>,
        Zhang Lei <zhang.lei@...fujitsu.com>
Subject: Re: [PATCH v5] arm64: Add workaround for Fujitsu A64FX erratum 010001

On Tue, Feb 26, 2019 at 06:43:41PM +0000, James Morse wrote:
> From: Zhang Lei <zhang.lei@...fujitsu.com>
> 
> On the Fujitsu-A64FX cores ver(1.0, 1.1), memory access may cause
> an undefined fault (Data abort, DFSC=0b111111). This fault occurs under
> a specific hardware condition when a load/store instruction performs an
> address translation. Any load/store instruction, except non-fault access
> including Armv8 and SVE might cause this undefined fault.
> 
> The TCR_ELx.NFD1 bit is used by the kernel when CONFIG_RANDOMIZE_BASE
> is enabled to mitigate timing attacks against KASLR where the kernel
> address space could be probed using the FFR and suppressed fault on
> SVE loads.
> 
> Since this erratum causes spurious exceptions, which may corrupt
> the exception registers, we clear the TCR_ELx.NFDx=1 bits when
> booting on an affected CPU.
> 
> Signed-off-by: Zhang Lei <zhang.lei@...fujitsu.com>
> [Generated MIDR value/mask for __cpu_setup(), removed spurious-fault handler
>  and always disabled the NFDx bits on affected CPUs]
> Signed-off-by: James Morse <james.morse@....com>
> Tested-by: zhang.lei <zhang.lei@...fujitsu.com>

Queued for 5.1. Thanks.

-- 
Catalin