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From:   "Zhang, Lei" <zhang.lei@jp.fujitsu.com>
To:     'Catalin Marinas' <catalin.marinas@arm.com>
CC:     'Mark Rutland' <mark.rutland@arm.com>,
        "'will.deacon@arm.com'" <will.deacon@arm.com>,
        "'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>,
        "'linux-arm-kernel@lists.infradead.org'" 
        <linux-arm-kernel@lists.infradead.org>
Subject: RE: [PATCH v2 1/1] arm64: Add workaround for Fujitsu A64FX erratum
 010001
Thread-Topic: [PATCH v2 1/1] arm64: Add workaround for Fujitsu A64FX erratum
 010001
Thread-Index: AdSyLRrS1IDcSdJoRF6WCq7/B3VdwACYGWwAAMw1BtA=
Date:   Tue, 29 Jan 2019 10:54:51 +0000
Message-ID: <8898674D84E3B24BA3A2D289B872026A6A2C03E0@G01JPEXMBKW03>
References: <8898674D84E3B24BA3A2D289B872026A6A2A32D6@G01JPEXMBKW03>
 <8898674D84E3B24BA3A2D289B872026A6A2A32EB@G01JPEXMBKW03>
 <20190125180813.GM25901@arrakis.emea.arm.com>
In-Reply-To: <20190125180813.GM25901@arrakis.emea.arm.com>
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Hi Catalin,
> -----Original Message-----
> From: linux-arm-kernel
> [mailto:linux-arm-kernel-bounces@lists.infradead.org] On Behalf Of
> Catalin Marinas
> Sent: Saturday, January 26, 2019 3:08 AM
> To: Zhang, Lei/張 雷
> Cc: 'Mark Rutland'; 'will.deacon@arm.com';
> 'linux-kernel@vger.kernel.org';
> 'linux-arm-kernel@lists.infradead.org'
> Subject: Re: [PATCH v2 1/1] arm64: Add workaround for Fujitsu A64FX
> erratum 010001
> 
> IIUC, this can happen very early when the errata framework isn't yet
> ready. Given that this is not on a fast path (you already took a fault),
> I don't think it's worth optimising for cpus_have_cap() (and
> ARM64_WORKAROUND_FUJITSU_A64FX_0100001). I've seen Mark's comments on
> why checking MIDR in a preemptible context is not a good idea but I
> suspect your platform is homogeneous (i.e. not big.LITTLE).
Thanks for comment.
I will post a new patch to resolve fast path problem in today.
By the way our platform is homogeneous.


Best Regards,
Lei Zhang
zhang.lei@jp.fujitsu.com