Messages in this thread | | | Date | Thu, 21 Jul 2022 11:57:22 -0700 | Subject | Re: [PATCH v8 5/5] x86/tdx: Add Quote generation support | From | Sathyanarayanan Kuppuswamy <> |
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On 7/21/22 11:52 AM, Dave Hansen wrote: > On 7/21/22 11:42, Isaku Yamahata wrote: >> Regarding to the size of quote, there is no hard limit because it's for future >> usage. But here is a rough idea about it. >> >> - 4KB(1 page) can accommodate TDREPORT that is defined right now. >> - 128KB is too small for foreseen use cases. >> - 1MB is too big. big enough for future. > > Again, we're off in the weeds. > > How does the VMM know how much to read/write? I have a theory: the spec > says that R12 is: > > "Shared 4KB GPA as input – the memory contains a > TDREPORT_STRUCT." > > That's *A* 4KB GPA. The maximum is one 4KB page. That's the only thing > that makes sense because there's no length in the ABI anywhere. > > What am I missing?
I think you are looking into the old spec. Please check the version "FEBRUARY 2022"
Following are the ABI details:
R11 - TDG.VP.VMCALL< GetQuote > sub-function per Table 2-3 R12 - Shared GPA as input – the memory contains a TDREPORT_STRUCT. The same buffer is used as output – the memory contains a TD Quote. R13 - Size of shared GPA. The size must be 4KB-aligned.
-- Sathyanarayanan Kuppuswamy Linux Kernel Developer
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