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: <18578c5a-7a35-ab20-467c-80141b0410a8@intel.com>
Date:   Fri, 22 Jul 2022 12:13:23 -0700
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.9.1
Subject: Re: [PATCH v8 5/5] x86/tdx: Add Quote generation support
Content-Language: en-US
To:     Isaku Yamahata <isaku.yamahata@gmail.com>
Cc:     Kuppuswamy Sathyanarayanan 
        <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>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Kai Huang <kai.huang@intel.com>,
        Wander Lairson Costa <wander@redhat.com>,
        marcelo.cerri@canonical.com, tim.gardner@canonical.com,
        khalid.elmously@canonical.com, philip.cox@canonical.com,
        linux-kernel@vger.kernel.org
References: <20220609025220.2615197-1-sathyanarayanan.kuppuswamy@linux.intel.com>
 <20220609025220.2615197-6-sathyanarayanan.kuppuswamy@linux.intel.com>
 <403cfccb-7fff-ab0b-8ebd-e5b04e631571@intel.com>
 <20220722190524.GA3299911@ls.amr.corp.intel.com>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <20220722190524.GA3299911@ls.amr.corp.intel.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 7/22/22 12:05, Isaku Yamahata wrote:
>> So, the quote portion of this is basically a bidirectional blob sender.
>>  It's to send a blob between guest userspace to host userspace.
>>
>> Do we *REALLY* need specific driver functionality for this?  For
>> instance, is there no existing virtio device that can send blobs back
>> and forth?
> It's virtio-vsock.  If virtio-vsock is available, the communication works.
> However, some users would like to disable virtio-vsock on their environment for
> some reasons.  Even virtio at all.  Especially for confidential computing use
> case.  It's their choice.  It can't be assumed that virtio is available.
> 
> The goal is VMM-agnostic (but TDX-specific) interface for that.

You're basically saying that every confidential computing technology
should have its own host user <-> guest kernel <-> guest user ABI.
That's insanity.  If we do this, we need *one* interface that says "talk
to the hypervisor" that's common for all hypervisors and hardware
vendors, or at least more than *one*.

We don't need a way to talk to hypervisors for Intel systems and another
for AMD and yet another on whatever.