linux-kernel - Re: [PATCHv4 05/30] x86/tdx: Extend the confidential computing API to support TDX guests

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Message-ID: <4940a38f-282b-7ce6-4d4c-2db1072ed3ca@intel.com>
Date:   Thu, 24 Feb 2022 16:51:22 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        luto@...nel.org, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
        joro@...tes.org, jpoimboe@...hat.com, knsathya@...nel.org,
        pbonzini@...hat.com, sdeep@...are.com, seanjc@...gle.com,
        tony.luck@...el.com, vkuznets@...hat.com, wanpengli@...cent.com,
        thomas.lendacky@....com, brijesh.singh@....com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 05/30] x86/tdx: Extend the confidential computing API to
 support TDX guests

On 2/24/22 15:54, Kirill A. Shutemov wrote:
> 
>> Second, why have the global 'td_info' instead of just declaring it on
>> the stack.  It is only used within a single function.  Having it on the
>> stack is *REALLY* nice because the code ends up looking like:
>>
>> 	struct foo foo;
>> 	get_info(&foo);
>> 	cc_set_bar(foo.bar);
>>
>> The dependencies and scope are just stupidly obvious if you do that.
> Okay, I will rework it with plain gpa_width on stack and get_info(&gpa_width);
> Attributes will be needed after core enabling, so I will drop it from
> here.

I don't mind the 'struct tdx_info' if there's going to be more stuff in
it soon-ish.  Having a single member is fine for now.  Just make it
clear that the seamcall returns a bunch of stuff and only a subset of it
is used right now.