linux-kernel - Re: [PATCH v11 09/13] x86, sgx: basic routines for enclave page cache

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Date:   Tue, 19 Jun 2018 08:59:25 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     Dave Hansen <dave.hansen@...el.com>, x86@...nel.org,
        platform-driver-x86@...r.kernel.org, nhorman@...hat.com,
        npmccallum@...hat.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>,
        "open list:INTEL SGX" <intel-sgx-kernel-dev@...ts.01.org>
Subject: Re: [PATCH v11 09/13] x86, sgx: basic routines for enclave page cache

On Tue, Jun 19, 2018 at 05:57:53PM +0300, Jarkko Sakkinen wrote:
> On Fri, Jun 08, 2018 at 11:24:12AM -0700, Dave Hansen wrote:
> > On 06/08/2018 10:09 AM, Jarkko Sakkinen wrote:
> > > +static __init bool sgx_is_enabled(bool *lc_enabled)
> > >  {
> > >  	unsigned long fc;
> > >  
> > > @@ -41,12 +466,26 @@ static __init bool sgx_is_enabled(void)
> > >  	if (!(fc & FEATURE_CONTROL_SGX_ENABLE))
> > >  		return false;
> > >  
> > > +	*lc_enabled = !!(fc & FEATURE_CONTROL_SGX_LE_WR);
> > > +
> > >  	return true;
> > >  }
> > 
> > I'm baffled why lc_enabled is connected to the enclave page cache.
> 
> KVM works only with writable MSRs. Driver works both with writable
> and read-only MSRs.

That's not true, KVM can/will support SGX regardless of whether or not
Launch Control (LC) is available and/or enabled.  KVM does need to
know whether or not LC is enabled.

Back to Dave's question, LC isn't connected to the EPC management,
the LC code should be split into a separate patch.
 
> Thanks, I'll try my best to deal with all this :-)
> 
> /Jarkko