Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 15 Feb 2022 10:42:42 -0800
From:   "Luck, Tony" <tony.luck@intel.com>
To:     Jue Wang <juew@google.com>
Cc:     Borislav Petkov <bp@alien8.de>, x86@kernel.org,
        linux-kernel@vger.kernel.org, patches@lists.linux.dev
Subject: Re: [PATCH] x86/mce: Add workaround for SKX/CLX/CPX spurious machine
 checks
Message-ID: <Ygv0IncyBA3pXR7Q@agluck-desk3.sc.intel.com>
References: <CAPcxDJ7nriZEJHF6dMPR7tQ+dGuueyRjw1NC+4CbjxiAT_S+ZA@mail.gmail.com>
 <20220208150945.266978-1-juew@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220208150945.266978-1-juew@google.com>
Precedence: bulk

On Tue, Feb 08, 2022 at 07:09:45AM -0800, Jue Wang wrote:
> +static bool quirk_skylake_repmov(void)
> +{
> +	u64 mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS);
> +	u64 misc_enable = __rdmsr(MSR_IA32_MISC_ENABLE);
> +
> +	if ((mcgstatus & MCG_STATUS_LMCES) &&
> +	    unlikely(misc_enable & MSR_IA32_MISC_ENABLE_FAST_STRING)) {
> +		u64 mc1_status = mce_rdmsrl(MSR_IA32_MCx_STATUS(1));
> +

Needs a comment that this big blob of logic is checking for a software
recoverable data fetch error.

> +		if ((mc1_status &
> +		     (MCI_STATUS_VAL|MCI_STATUS_OVER|MCI_STATUS_UC|MCI_STATUS_EN|
> +		      MCI_STATUS_ADDRV|MCI_STATUS_MISCV|MCI_STATUS_PCC|
> +		      MCI_STATUS_AR|MCI_STATUS_S)) ==
> +		    (MCI_STATUS_VAL|MCI_STATUS_UC|MCI_STATUS_EN|MCI_STATUS_ADDRV|
> +		     MCI_STATUS_MISCV|MCI_STATUS_AR|MCI_STATUS_S)) {
> +			msr_clear_bit(MSR_IA32_MISC_ENABLE,
> +				      MSR_IA32_MISC_ENABLE_FAST_STRING_BIT);
> +			mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
> +			mce_wrmsrl(MSR_IA32_MCx_STATUS(1), 0);
> +			pr_err_once("Errata detected, disable fast string copy instructions.\n");
> +			return true;
> +		}
> +	}
> +	return false;
> +}

Otherwise:

Reviewed-by: Tony Luck <tony.luck@intel.com>

-Tony