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

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Message-ID: <aafa64b6-b5a0-fbfb-8b1f-995044745ccd@fortanix.com>
Date:   Tue, 19 Jun 2018 08:44:40 -0700
From:   Jethro Beekman <jethro@...tanix.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.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 2018-06-19 07:08, Jarkko Sakkinen wrote:
> 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?

Just the last sentence.

> /Jarkko
Jethro


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