linux-kernel - Re: [PATCH v22 01/24] x86/cpufeatures: x86/msr: Add Intel SGX hardware bits

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Date:   Tue, 24 Sep 2019 18:25:20 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        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,
        serge.ayoun@...el.com, shay.katz-zamir@...el.com,
        haitao.huang@...el.com, andriy.shevchenko@...ux.intel.com,
        tglx@...utronix.de, kai.svahn@...el.com, josh@...htriplett.org,
        luto@...nel.org, kai.huang@...el.com, rientjes@...gle.com,
        cedric.xing@...el.com, Kai Huang <kai.huang@...ux.intel.com>
Subject: Re: [PATCH v22 01/24] x86/cpufeatures: x86/msr: Add Intel SGX
 hardware bits

On Tue, Sep 24, 2019 at 09:11:50AM -0700, Sean Christopherson wrote:
> With respect to more SGX feature flags, the original changelog even
> stated "with more expected in the not-too-distant future".

That means nothing, you know that, right? :)

There's a big difference between expectation and it actually happening
and besides, the longterm plan with all those feature words which are
scattered, is to propagate them to proper ->x86_capability[] words once
the number of feature bits used is gradually growing.

Also,...

> I'm not arguing that this isn't ugly, just want to make it clear that
> we're not wantonly throwing junk into the kernel.  I'm all for a dedicated
> SGX word, it makes our lives easier.

... you didn't do the first-8-bits-need-to-match-the-CPUID-leaf for KVM
thing then, you're doing now. Which would make word 8 half-hard-coded
and the other half Linux-defined.

Which makes a separate leaf look much better now. :)

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette