linux-kernel - Re: [PATCH v8 5/5] x86/tdx: Add Quote generation support

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Date:   Mon, 25 Jul 2022 15:06:34 -0700
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     "Nakajima, Jun" <jun.nakajima@...el.com>,
        "Hansen, Dave" <dave.hansen@...el.com>
Cc:     Isaku Yamahata <isaku.yamahata@...il.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" <x86@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        "Huang, Kai" <kai.huang@...el.com>,
        Wander Lairson Costa <wander@...hat.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>,
        "tim.gardner@...onical.com" <tim.gardner@...onical.com>,
        "khalid.elmously@...onical.com" <khalid.elmously@...onical.com>,
        "Cox, Philip" <philip.cox@...onical.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 5/5] x86/tdx: Add Quote generation support

Hi Jun,

On 7/25/22 2:56 PM, Nakajima, Jun wrote:
> 
>> On Jul 25, 2022, at 1:23 PM, Hansen, Dave <dave.hansen@...el.com> wrote:
>>
>> On 7/25/22 13:19, Nakajima, Jun wrote:
>>> 3. Need to be available in minimal/early runtime environments,
>>> including pre-boot, e.g. guest BIOS, no user-space yet.
>>
>> Jun, are we talking about the same thing here?  This patch is for a
>> guest userspace -> guest kernel ABI.  This facility is *FOR* userspace.
>> It can't possibly be used before userspace is running.
>>
>> I'm horribly confused.
> 
> I responded to one of Sathya’s questions, especially why we have the GetQuote in GHCI. 
> And the hypervisor needs to implement that anyway because it doesn’t matter (or doesn’t know) whether the TD guest is running in BIOS, the kernel, or userspace. Of course, the facility in this patch is for userspace, but we don’t want to suggest to implement two different GetQuote code paths for guests, depending on the guest state, e.g. in the OS (kernel or userspace) or guest BIOS.

Ok. Since both host and QE need to support GetQuote hypercall to
handle attestation request from the BIOS, QE/host may want to use
the same communication model for requests from the guest user space
as well.

> 
> --- 
> Jun
> 
> 
> 
> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer