linux-kernel - Re: [PATCH v5 3/3] x86/tdx: Add Quote generation support

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Message-ID: <20220507004236.5p5dyksftge7wwr3@black.fi.intel.com>
Date:   Sat, 7 May 2022 03:42:36 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Kai Huang <kai.huang@...el.com>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>, Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Wander Lairson Costa <wander@...hat.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/3] x86/tdx: Add Quote generation support

On Fri, May 06, 2022 at 12:11:03PM +1200, Kai Huang wrote:
> Kirill, what's your opinion?

I said before that I think DMA API is the right tool here.

Speculation about future of DMA in TDX is irrelevant here. If semantics
change we will need to re-evaluate all users. VirtIO uses DMA API and it
is conceptually the same use-case: communicate with the host.

But vmap() + set_memory_decrypted() also works and Sathya already has code
for it. I'm fine with this.

Going a step below to manual MapGPA() is just wrong. We introduced
abstructions for a reason. Protocol of changing GPA status is not trivial.
We should not spread it across all kernel codebase.

-- 
 Kirill A. Shutemov