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

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Date:   Thu, 21 Jul 2022 09:49:03 -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 09:42, 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.