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Message-ID: <a65473db-b307-c076-6d2f-8f2084d81eb5@intel.com>
Date: Thu, 21 Jul 2022 10:02:05 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: 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
Cc: "H . Peter Anvin" <hpa@...or.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Tony Luck <tony.luck@...el.com>,
Andi Kleen <ak@...ux.intel.com>,
Kai Huang <kai.huang@...el.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 v8 5/5] x86/tdx: Add Quote generation support
On 7/21/22 09:54, Sathyanarayanan Kuppuswamy wrote:
>
> On 7/21/22 9:49 AM, Dave Hansen wrote:
>> On 7/21/22 09:42, Sathyanarayanan Kuppuswamy wrote:
>>> On 7/21/22 9:08 AM, Dave Hansen wrote:
>>>> On 6/8/22 19:52, Kuppuswamy Sathyanarayanan wrote:
>>>>> For shared buffer allocation, alternatives like using the DMA API is
>>>>> also considered. Although it simpler to use, it is not preferred because
>>>>> dma_alloc_*() APIs require a valid bus device as argument, which would
>>>>> need converting the attestation driver into a platform device driver.
>>>>> This is unnecessary, and since the attestation driver does not do real
>>>>> DMA, there is no need to use real DMA APIs.
>>>> Let's actually try to walk through the requirements for the memory
>>>> allocation here.
>>>>
>>>> 1. The guest kernel needs to allocate some guest physical memory
>>>> for the attestation data buffer
>>> Physically contiguous memory.
>> Remind me how large the quote structures are.
> It depends on the attestation service. In addition to TDREPORT (1K size),
> during quote generation, additional data can be included in the signed
> quote. So the spec allows variable length. User agent will communicate with
> attestation service to identify the appropriate buffer length. Our test
> uses 8K buffers
What is this "additional data"? Is that "REPORTDATA" from the TDX
module spec?
"Additional REPORTDATA, a 64-byte value, is provided by the
guest TD to be included in the TDG.MR.REPORT."
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