On Wed, 2022-04-20 at 23:57 -0700, Isaku Yamahata wrote: > On Wed, Apr 20, 2022 at 07:42:06PM -0700, > Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> 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. > > 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 > > As Kai said, there is no requirement for multiple GetQuote in parallel, it's > okay to support only single request at the same 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. Sorry I missed this in the spec. Then as I mentioned above, TD should check which buffer has GET_QUOTE_IN_FLIGHT bit cleared to determine which GetQuote request is done? I guess this is the only way. Anyway, supporting single request only is fine to me. Just needs some explanation in comments or commit message. -- Thanks, -Kai
