linux-kernel - Re: [PATCH v6 03/11] x86: define IA32_FEATURE_CONTROL.SGX

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Message-ID: <20171128204734.gcz2y3pold4nyhxe@linux.intel.com>
Date:   Tue, 28 Nov 2017 22:47:34 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     platform-driver-x86@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Len Brown <len.brown@...el.com>,
        Kyle Huey <me@...ehuey.com>, Haim Cohen <haim.cohen@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Jim Mattson <jmattson@...gle.com>,
        Grzegorz Andrejczuk <grzegorz.andrejczuk@...el.com>
Subject: Re: [PATCH v6 03/11] x86: define IA32_FEATURE_CONTROL.SGX_ENABLE

On Tue, Nov 28, 2017 at 09:13:18AM -0800, Sean Christopherson wrote:
> On Sat, 2017-11-25 at 21:29 +0200, Jarkko Sakkinen wrote:
> > From: Sean Christopherson <sean.j.christopherson@...el.com>
> > 
> > When IA32_FEATURE_CONTROL.SGX_ENABLE and IA32_FEATURE_CONTROL.LOCK are
> > set by the pre-boot firmware, SGX is usable by the OS.
> 
> This implies that only pre-boot firmware can write feature control, which is not
> true.  What about:
> 
>     SGX instructions (ENCLS and ENCLU) are usable if and only if SGX_ENABLE is
>     set in the IA32_FEATURE_CONTROL MSR and said MSR is locked.

You are correct, thanks. I'll fix this for v7.

/Jarkko