Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <7cadc7777238a50dec4c18119e1c68fd3c5cfe96.camel@intel.com>
Subject: Re: [PATCH v5 3/3] x86/tdx: Add Quote generation support
From:   Kai Huang <kai.huang@intel.com>
To:     "Kirill A. Shutemov" <kirill@shutemov.name>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H . Peter Anvin" <hpa@zytor.com>, Tony Luck <tony.luck@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Wander Lairson Costa <wander@redhat.com>,
        Isaku Yamahata <isaku.yamahata@gmail.com>,
        marcelo.cerri@canonical.com, tim.gardner@canonical.com,
        khalid.elmously@canonical.com, philip.cox@canonical.com,
        linux-kernel@vger.kernel.org
Date:   Tue, 10 May 2022 13:40:05 +1200
In-Reply-To: <20220510013038.ggubvsrwf7pyoamk@box.shutemov.name>
References: <40ccd0f0-35a1-5aa7-9e51-25ab196d79e5@linux.intel.com>
         <2ed5c9cc316950a5a47ee714715b7980f358a140.camel@intel.com>
         <ab17102c-0cb7-87d3-3494-969866d64573@linux.intel.com>
         <d53696f85ada39a91a3685c61d177c582810772e.camel@intel.com>
         <d63d2774-c44d-27da-74b6-550935a196fd@intel.com>
         <dca06ffa36abe9989f0a7abaeafc83c1a7250651.camel@intel.com>
         <20220507004236.5p5dyksftge7wwr3@black.fi.intel.com>
         <45d184273f1950320843f6696eb3071f7d354fd3.camel@intel.com>
         <20220509120927.7rg6v5pyc3f4pxsh@box.shutemov.name>
         <75d4755c9a376df2e98a267e10e60da3bd178b17.camel@intel.com>
         <20220510013038.ggubvsrwf7pyoamk@box.shutemov.name>
Content-Type: text/plain; charset="UTF-8"
User-Agent: Evolution 3.42.4 (3.42.4-1.fc35) 
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Precedence: bulk

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