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

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Message-ID: <9a85546c-954d-446d-28d5-8a88be5a1ce3@linux.intel.com>
Date:   Thu, 21 Jul 2022 11:31:09 -0700
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...el.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

Hi Dave,

On 7/21/22 10:19 AM, Dave Hansen wrote:
> How many bytes does the TDX module read from and write to the guest
> physical address space?  What are the absolute limits?  What is the
> minimum and the maximum that the kernel needs to handle?

Minimum is 1K (equal to TDREPORT size, on input Quoting Enclave reads 1K TDREPORT
data from GPA)

Maximum size is not defined in the spec. I think for future compatibility, spec
does not limit the quote size. For most cases, I think 8K should be big enough.

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer