linux-kernel - Re: [PATCH v14 04/19] x86/cpufeatures: Add SGX feature bits

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Date:   Thu, 27 Sep 2018 16:16:42 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>
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, serge.ayoun@...el.com,
        shay.katz-zamir@...el.com, linux-sgx@...r.kernel.org,
        andriy.shevchenko@...ux.intel.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        David Wang <davidwang@...oxin.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>,
        Jia Zhang <qianyue.zj@...baba-inc.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>, He Chen <he.chen@...ux.intel.com>,
        Luwei Kang <luwei.kang@...el.com>, kvm@...r.kernel.org,
        Radim Krčmář <rkrcmar@...hat.com>,
        Piotr Luc <Piotr.Luc@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v14 04/19] x86/cpufeatures: Add SGX feature bits

On Wed, Sep 26, 2018 at 01:36:17PM +0200, Borislav Petkov wrote:
> On Wed, Sep 26, 2018 at 02:11:39PM +0300, Jarkko Sakkinen wrote:
> > Thank you. I guess I understand what you want me to do i.e.
> > 
> > +       { X86_FEATURE_SGX1,             CPUID_EAX,  0, 0x00000012, 0 },
> > +       { X86_FEATURE_SGX2,             CPUID_EAX,  1, 0x00000012, 0 },
> > +       { X86_FEATURE_ENCLV,            CPUID_EAX,  5, 0x00000012, 0 },
> > +       { X86_FEATURE_ENCLS_C,          CPUID_EAX,  6, 0x00000012, 0 },
> 
> Yap.
> 
> > What puzzles me is that I cannot find any call site for
> > get_scattered_cpuid_leaf():
> > 
> > $ git grep get_scattered
> > arch/x86/kernel/cpu/cpu.h:extern u32 get_scattered_cpuid_leaf(unsigned int level,
> > arch/x86/kernel/cpu/scattered.c:u32 get_scattered_cpuid_leaf(unsigned int level, unsigned int sub_leaf,
> > arch/x86/kernel/cpu/scattered.c:EXPORT_SYMBOL_GPL(get_scattered_cpuid_leaf);
> 
> That used to be used in kvm last, see b7b27aa011a1df42728d1768fc181d9ce69e6911,
> which removed it.
> 
> And it got added by
> 
>   47bdf3378d62 ("x86/cpuid: Provide get_scattered_cpuid_leaf()")
> 
> Lemme add those people to CC.
> 
> If no one wants it, feel free to decomission it.

Still kind of leaves me puzzled about the situation :-) Why this wasn't
used for example to replace detect_vmx_virtcap()?

/Jarkko