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Date:   Tue, 5 Oct 2021 22:03:09 -0700
From:   Josh Poimboeuf <jpoimboe@redhat.com>
To:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
        David Hildenbrand <david@redhat.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Juergen Gross <jgross@suse.com>, Deep Shah <sdeep@vmware.com>,
        VMware Inc <pv-drivers@vmware.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, Peter H Anvin <hpa@zytor.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Kirill Shutemov <kirill.shutemov@linux.intel.com>,
        Sean Christopherson <seanjc@google.com>,
        Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 03/11] x86/cpufeatures: Add TDX Guest CPU feature
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References: <20211005025205.1784480-1-sathyanarayanan.kuppuswamy@linux.intel.com>
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On Tue, Oct 05, 2021 at 09:33:35PM -0700, Kuppuswamy, Sathyanarayanan wrote:
> 
> 
> On 10/5/21 8:42 PM, Josh Poimboeuf wrote:
> > > is_tdx_guest was mainly introduced to support cc_platform_has()
> > > API in early boot calls (similar to sme_me_mask in AMD code).
> > > Regarding FEATURE flag it will be useful for userspace tools to
> > > check the TDX feature support.
> > FEATURE flags can also be checked in the kernel, with boot_cpu_has().
> > Or am I missing something?
> 
> Yes, previously we have been using x86_feature_enabled() check in
> cc_platform_has() call. Now with the introduction of is_tdx_guest
> global variable, we don't use it in kernel. But I still want to
> keep the feature flag for user space use case.

I'm not suggesting getting rid of the feature flag.  I'm suggesting
getting rid of the global variable.  Is there a reason you can't check
the feature flag instead of checking the global variable?

-- 
Josh