linux-kernel - Re: [PATCH v2 1/2] x86/speculation: Fix incorrect MDS/TAA mitigation status

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Message-ID: <7EAED44C-A93E-405E-B57B-89AC3F779A70@alien8.de>
Date:   Fri, 15 Nov 2019 18:09:25 +0100
From:   Boris Petkov <bp@...en8.de>
To:     Waiman Long <longman@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
CC:     linux-kernel@...r.kernel.org, Josh Poimboeuf <jpoimboe@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Mark Gross <mgross@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH v2 1/2] x86/speculation: Fix incorrect MDS/TAA mitigation status

On November 15, 2019 5:14:44 PM GMT+01:00, Waiman Long <longman@...hat.com> wrote:
>For MDS vulnerable processors with TSX support, enabling either MDS or
>TAA mitigations will enable the use of VERW to flush internal processor
>buffers at the right code path. IOW, they are either both mitigated
>or both not. However, if the command line options are inconsistent,
>the vulnerabilites sysfs files may not report the mitigation status
>correctly.
>
>For example, with only the "mds=off" option:
>
>  vulnerabilities/mds:Vulnerable; SMT vulnerable
>vulnerabilities/tsx_async_abort:Mitigation: Clear CPU buffers; SMT
>vulnerable
>
>The mds vulnerabilities file has wrong status in this case. Similarly,
>the taa vulnerability file will be wrong with mds mitigation on, but
>taa off.
>
>Change taa_select_mitigation() to sync up the two mitigation status
>and have them turned off if both "mds=off" and "tsx_async_abort=off"
>are present.
>
>Both hw-vuln/mds.rst and hw-vuln/tsx_async_abort.rst are updated
>to emphasize the fact that both "mds=off" and "tsx_async_abort=off"
>have to be specified together for processors that are affected by both
>TAA and MDS to be effective. As kernel-parameter.txt references both
>documents above, it is not necessary to update it.

What about kernel-parameters.txt?

-- 
Sent from a small device: formatting sux and brevity is inevitable.