linux-kernel - Re: [PATCH v29 00/20] Intel SGX foundations

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Message-ID: <87pnb6xqly.fsf@nanos.tec.linutronix.de>
Date:   Thu, 14 May 2020 21:29:13 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Borislav Petkov <bp@...en8.de>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     "Dr. Greg" <greg@...ellic.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-sgx@...r.kernel.org,
        akpm@...ux-foundation.org, dave.hansen@...el.com,
        nhorman@...hat.com, npmccallum@...hat.com, haitao.huang@...el.com,
        andriy.shevchenko@...ux.intel.com, kai.svahn@...el.com,
        josh@...htriplett.org, luto@...nel.org, kai.huang@...el.com,
        rientjes@...gle.com, cedric.xing@...el.com, puiterwijk@...hat.com
Subject: Re: [PATCH v29 00/20] Intel SGX foundations

Borislav Petkov <bp@...en8.de> writes:

> On Thu, May 14, 2020 at 09:15:59AM -0700, Sean Christopherson wrote:
>> I'm not opposed to adding a kernel param to disable SGX.  At one point
>> there was a proposal to extend clearcpuid to allow disabling multiple
>> feature bits, but it looks like that went the way of the dodo.

clearcpuid is a trainwreck which should have never happened.

>> Note, such a param would disable SGX entirely, e.g. clear the feature bit
>> in /proc/cpuinfo and prevent any in-kernel SGX code from running.
>
> It is a usual practice for big features like SGX to add a
> "nosgx" cmdline param to disable it in case something goes
> south. We do this for all features - see all "no*" switches in
> Documentation/admin-guide/kernel-parameters.txt

Correct.

Thanks,

        tglx