linux-kernel - Re: [RFC v2-fix-v2 1/1] x86: Introduce generic protected guest abstractionn

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Date:   Mon, 7 Jun 2021 15:26:51 -0700
From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>,
        "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        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>,
        linux-kernel@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [RFC v2-fix-v2 1/1] x86: Introduce generic protected guest
 abstractionn



On 6/7/21 1:14 PM, Borislav Petkov wrote:
> On Mon, Jun 07, 2021 at 10:55:44PM +0300, Kirill A. Shutemov wrote:
>> I think conversions like this are wrong: relocate_kernel(), which got
>> called here, only knows how to deal with SME, not how to handle some
>> generic case.
> 
> What do you mean wrong? Wrong for TDX?
> 
> If so, then that can be
> 
> protected_guest_has(SME)
> 
> or so, which would be false on Intel.

I agree. Since most of the code changed in this patch is
not applicable to TDX, it might need product specific or
new function specific flags.

> 
> And this patch was only a mechanical conversion to see how it would look
> like.
> 
>> If code is written to handle a specific technology we need to stick
>> with a check that makes it clear. Trying to make sound generic only
>> leads to confusion.
> 
> Sure, fine by me.
> 
> And I don't want a zoo of gazillion small checking functions per
> technology. sev_<something>, tdx_<something>, yadda yadda.
> 
> So stuff better be unified. Even if you'd have vendor-specific defines
> you hand into that function - and you will have such - it is still much
> saner than what it turns into with the AMD side of things.

Agree. Currently we share code with AMD SEV in memory encryption support and
string I/O handling code. So defining common flag for such code is
useful.

> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer