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

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Date:   Tue, 19 Jun 2018 17:08:15 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Jethro Beekman <jethro@...tanix.com>
Cc:     x86@...nel.org, platform-driver-x86@...r.kernel.org,
        dave.hansen@...el.com, sean.j.christopherson@...el.com,
        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 Fri, Jun 08, 2018 at 11:21:48AM -0700, Jethro Beekman wrote:
> On 2018-06-08 10:09, Jarkko Sakkinen wrote:
> > +/*
> > + * Writing the LE hash MSRs is extraordinarily expensive, e.g.
> > + * 3-4x slower than normal MSRs, so we use a per-cpu cache to
> > + * track the last known value of the MSRs to avoid unnecessarily
> > + * writing the MSRs with the current value.  Because most Linux
> > + * kernels will use an LE that is signed with a non-Intel key,
> 
> I don't think you can predict what most Linux kernels will be doing. I think
> not initializing the cache to the CPU's initial value is fine, but this
> particular argument shouldn't appear in the rationale.

Are you just referring to the last sentence or the whole paragraph?

/Jarkko