From: Catalin Marinas <catalin.marinas@arm.com>
To: "Zhang, Lei" <zhang.lei@jp.fujitsu.com>
Cc: 'Mark Rutland' <mark.rutland@arm.com>,
"'linux-arm-kernel@lists.infradead.org'"
<linux-arm-kernel@lists.infradead.org>,
"'will.deacon@arm.com'" <will.deacon@arm.com>,
"'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/1] arm64: Add workaround for Fujitsu A64FX erratum 010001
Date: Fri, 25 Jan 2019 18:08:14 +0000 [thread overview]
Message-ID: <20190125180813.GM25901@arrakis.emea.arm.com> (raw)
In-Reply-To: <8898674D84E3B24BA3A2D289B872026A6A2A32EB@G01JPEXMBKW03>
On Tue, Jan 22, 2019 at 08:54:33AM +0000, Zhang, Lei wrote:
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index efb7b2c..37e4f18 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -666,6 +666,28 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
> return 0;
> }
>
> +static int do_bad_unknown_63(unsigned long addr, unsigned int esr, struct pt_regs *regs)
> +{
> + /*
> + * On some variants of the Fujitsu-A64FX cores ver(1.0, 1.1),
> + * memory accesses may spuriously trigger data aborts with
> + * DFSC=0b111111.
> + */
> + if (IS_ENABLED(CONFIG_FUJITSU_ERRATUM_010001)) {
> + if (cpus_have_cap(ARM64_WORKAROUND_FUJITSU_A64FX_0100001)) {
> + return 0;
> + } else { /* cpu capabilities maybe not ready*/
> + unsigned int current_cpu_midr = read_cpuid_id();
> + const struct midr_range fujitsu_a64fx_midr_range = {
> + MIDR_FUJITSU_A64FX, MIDR_CPU_VAR_REV(0, 0), MIDR_CPU_VAR_REV(1, 0)
> + };
> + if (is_midr_in_range(current_cpu_midr, &fujitsu_a64fx_midr_range) == TRUE)
> + return 0;
> + }
> + }
> + return do_bad(addr, esr, regs);
> +}
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).
--
Catalin
next prev parent reply other threads:[~2019-01-25 18:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-22 8:54 [PATCH v2 0/1] arm64: Add workaround for Fujitsu A64FX erratum 010001 Zhang, Lei
2019-01-22 8:54 ` [PATCH v2 1/1] " Zhang, Lei
2019-01-25 18:08 ` Catalin Marinas [this message]
2019-01-29 10:54 ` Zhang, Lei
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