Messages in this thread | | | Date | Thu, 21 Apr 2022 07:53:39 -0700 | Subject | Re: [PATCH v3 4/4] platform/x86: intel_tdx_attest: Add TDX Guest attestation interface driver | From | Sathyanarayanan Kuppuswamy <> |
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On 4/20/22 11:57 PM, Isaku Yamahata wrote: > On Wed, Apr 20, 2022 at 07:42:06PM -0700, > Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com> wrote: > >> >> >> On 4/20/22 5:11 PM, Kai Huang wrote: >>> On Wed, 2022-04-20 at 16:45 -0700, Sathyanarayanan Kuppuswamy wrote: >>>> If we want to support multiple GetQuote requests in parallel, then we >>>> need some way to uniquely identify the GetQuote requests. So that when >>>> we get completion notification, we can understand which request is >>>> completed. This part is not mentioned/discussed in ABI spec. So we want >>>> to serialize the requests for now. >>>> >>> >>> Yes it's unfortunate that this part (whether concurrent GetQuote requests are >>> supported by TDX architecture) is not explicitly mentioned in GHCI spec. I am >>> fine with only supporting GetQuote requests one by one. AFAICT there's no >>> request to support concurrent GetQuote requests anyway. What concerns me is >>> exactly how explain this. >>> >>> As I said, we have GET_QUOTE_IN_FLIGHT flag now. Theoretically, you can queue >>> multiple GetQuote requests, and when you receive the interrupt, you check which >>> buffer has GET_QUOTE_IN_FLIGHT cleared. That buffer is the one with Quote >>> ready. However I am not 100% sure whether above will always work. Interrupt >>> can get lost when there are multiple Quotes ready in multiple buffer in very >>> short time period, etc? Perhaps Isaku can provide more input here. >> >> Either supported or not, it should be mentioned in the GHCI spec. Currently, >> there are no details related to it. If it is supported, the specification >> should include the protocol to use. >> >> I will check with Isaku about it. > > The spec says that TD can call multiple GetQuote requests in parallel.
Sorry, I missed the above content. Thanks for pointing out.
> > TDG.VP.VMCALL<GetQuote> API allows one TD to issue multiple requests. It's > implementation specific that how many concurrent requests are allowed. The TD > should be able to handle TDG.VP.VMCALL_RETRY if it chooses to issue multiple > requests simultaneously
Do you know why we should handle VMCALL_RETRY case? IIUC, as per above spec, if each request we send uses different GPA buffer, then we should not even worry about checking for IN_FLIGHT status. right?
> > As Kai said, there is no requirement for multiple GetQuote in parallel, it's > okay to support only single request at the same time.
For now I will leave it as single request at a time.
> > While the status is GET_QUOTE_IN_FLIGHT, VMM owns the shared GPA. The > attestation driver should wait for GET_QUOTE_IN_FLIGHT to be cleared before > sending next request.
-- Sathyanarayanan Kuppuswamy Linux Kernel Developer
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