linux-kernel - Re: [RESEND PATCH v4 2/2] arm64: Add software workaround for Falkor erratum 1041

Open Source and information security mailing list archives

Message-ID: <39cc5f8d-be16-c437-28f8-1bc8601757af@codeaurora.org>
Date:   Mon, 11 Dec 2017 16:26:04 -0600
From:   Shanker Donthineni <shankerd@...eaurora.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-efi@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Robin Murphy <robin.murphy@....com>,
        kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RESEND PATCH v4 2/2] arm64: Add software workaround for Falkor
 erratum 1041

Thanks Mark, I'll post v5 patch without alternatives. 

On 12/11/2017 04:45 AM, Mark Rutland wrote:
> Hi,
> 
> On Sun, Dec 10, 2017 at 08:03:43PM -0600, Shanker Donthineni wrote:
>> +/**
>> + * Errata workaround prior to disable MMU. Insert an ISB immediately prior
>> + * to executing the MSR that will change SCTLR_ELn[M] from a value of 1 to 0.
>> + */
>> +	.macro pre_disable_mmu_workaround
>> +#ifdef CONFIG_QCOM_FALKOR_ERRATUM_E1041
>> +alternative_if ARM64_WORKAROUND_QCOM_FALKOR_E1041
>> +	isb
>> +alternative_else_nop_endif
>> +#endif
>> +	.endm
> 
> There's really no need for this to be an alternative. It makes the
> kernel larger and more complex due to all the altinstr data and probing
> code.
> 
> As Will suggested last time [1], please just use the ifdef, and always
> compile-in the extra ISB if CONFIG_QCOM_FALKOR_ERRATUM_E1041 is
> selected. Get rid of the alternatives and probing code.
> 
> All you need here is:
> 
> 	/*
> 	 * Some Falkor parts make errant speculative instruction fetches
> 	 * when SCTLR_ELx.M is cleared. An ISB before the write to
> 	 * SCTLR_ELx prevents this.
> 	 */
> 	.macro pre_disable_mmu_workaround
> #ifdef
> 	isb
> #endif
> 	.endm
> 
>> +
>> +	.macro pre_disable_mmu_early_workaround
>> +#ifdef CONFIG_QCOM_FALKOR_ERRATUM_E1041
>> +	isb
>> +#endif
>> +	.endm
>> +
> 
> ... and we don't need a special early variant.
> 
> Thanks,
> Mark.
> 
> [1] https://lkml.kernel.org/r/20171201112457.GE18083@arm.com
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

-- 
Shanker Donthineni
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives