linux-kernel - Re: [PATCH v7 01/12] x86/tdx: Add Intel ARCH support to cc_platform

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Message-ID: <8b9f6f88-83b8-1e52-6d56-8dd7a4cbfabb@intel.com>
Date:   Thu, 16 Sep 2021 12:57:26 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Juergen Gross <jgross@...e.com>, Deep Shah <sdeep@...are.com>,
        VMware Inc <pv-drivers@...are.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Peter H Anvin <hpa@...or.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 01/12] x86/tdx: Add Intel ARCH support to
 cc_platform_has()

On 9/16/21 12:06 PM, Borislav Petkov wrote:
> On Thu, Sep 16, 2021 at 11:44:48AM -0700, Dave Hansen wrote:
>> How did this end up out of line?  This means that if you compile-time
>> enable support for even *one* "cc" platform, you can't optimize the
>> calls away.  This ends up being at *LEAST* two calls, just to get an
>> unconditional "false".  That just seems silly.
>>
>> I know this is a comment more about the cc_platform_has() series that
>> this one, but this compounds the problem.
> Posting here too for the wider audience - follow this thread pls:
> 
> https://lkml.kernel.org/r/9d4fc3f8ea7b325aaa1879beab1286876f45d450.1631141919.git.thomas.lendacky@amd.com

It sounds like the argument boils down to: out-of-line is cleaner,
especially considering the cross-arch implementation.  Inlines can turn
into a mess, so make it out-of-line unless an *actual* real-world
benefit emerges.