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Subject: Re: [PATCH] x86/pkeys: Manually set X86_FEATURE_OSPKE to preserve
 existing changes
To:     Dave Hansen <dave.hansen@intel.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org
Cc:     "H. Peter Anvin" <hpa@zytor.com>, linux-kernel@vger.kernel.org,
        Dave Hansen <dave.hansen@linux.intel.com>
References: <20200226231615.13664-1-sean.j.christopherson@intel.com>
 <950b249a-f47d-0adc-80dd-68d397e4de4f@intel.com>
From:   Jacob Keller <jacob.e.keller@intel.com>
Organization: Intel Corporation
Message-ID: <3d869bdf-5ca7-d2ea-cc85-eb461b37b207@intel.com>
Date:   Wed, 26 Feb 2020 15:40:30 -0800
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On 2/26/2020 3:32 PM, Dave Hansen wrote:
> On 2/26/20 3:16 PM, Sean Christopherson wrote:
>> Explicitly set X86_FEATURE_OSPKE via set_cpu_cap() instead of calling
>> get_cpu_cap() to pull the feature bit from CPUID after enabling CR4.PKE.
> 
> First of all,
> 
> Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
> 
> I don't remember whether it was you or someone else inside Intel, but
> someone was tripping over this recently.
> 
> I do think we need a bit more care in how we deal with dynamic CPUID
> bits.  I think you'd agree that it's a bit haphazard.  For instance, I
> went looking for where we set X86_FEATURE_OSXSAVE after the
> 
>         cr4_set_bits(X86_CR4_OSXSAVE);
> 
> inside fpu__init_cpu_xstate() makes it appear.  I couldn't find one, not
> that we would notice since we suppress it from /proc/cpuinfo.
> 


I tripped over it. It's possible someone else has as well, but I haven't
heard from anyone else.

Thanks,
Jake