linux-kernel - Re: [RFC v1 09/26] x86/tdx: Handle CPUID via #VE

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Date:   Sun, 7 Feb 2021 14:31:28 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v1 09/26] x86/tdx: Handle CPUID via #VE

On 2/7/21 12:29 PM, Kirill A. Shutemov wrote:
>> Couldn't you just have one big helper that takes *all* the registers
>> that get used in any TDVMCALL and sets all the rcx bits?  The users
>> could just pass 0's for the things they don't use.
>>
>> Then you've got the ugly inline asm in one place.  It also makes it
>> harder to screw up the 'rcx' mask and end up passing registers you
>> didn't want into a malicious VMM.
> For now we only pass down R10-R15, but the interface allows to pass down
> much wider set of registers, including XMM. How far do we want to get it?

Just do what we immediately need: R10-R15.