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

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Date:   Tue, 10 May 2022 13:40:05 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        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 Tue, 2022-05-10 at 04:30 +0300, Kirill A. Shutemov wrote:
> On Tue, May 10, 2022 at 11:54:12AM +1200, Kai Huang wrote:
> > On Mon, 2022-05-09 at 15:09 +0300, Kirill A. Shutemov wrote:
> > > On Mon, May 09, 2022 at 03:37:22PM +1200, Kai Huang wrote:
> > > > On Sat, 2022-05-07 at 03:42 +0300, Kirill A. Shutemov wrote:
> > > > > 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.
> > > > 
> > > > Virtio is designed for device driver to use, so it's fine to use DMA API. And
> > > > real DMA can happen to the virtio DMA buffers.  Attestation doesn't have such
> > > > assumption.
> > > 
> > > Whether attestation driver uses struct device is implementation detail.
> > > I don't see what is you point.
> > 
> > No real DMA is involved in attestation.
> 
> As with VirtIO. So what?
> 

No real DMA can happen to virtio buffer.  Consider DPDK which uses virtio +
vhost-user.  But I don't want to argue anymore about this topic. :)

-- 
Thanks,
-Kai