On Tue, Apr 19, 2022 at 06:26:43PM -0700, Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> wrote: > On 4/19/22 6:20 PM, Isaku Yamahata wrote: > > If timeout occurs, the state of adev->tdquote_buf is unknown. It's not safe > > to continue to using adev->tdquote_buf. VMM would continue to processing > > getquote request with this buffer. What if TDX_CMD_GEN_QUOTE is issued again, > > and tdquote_buf is re-used? > > This part is not clearly discussed in the specification. May be spec > should define some reasonable timeout and teardown details. > > Regarding not using this buffer again, what happens if we de-allocate > it on timeout and the host still updates it? Until GET_QUOTE_IN_FLIGHT is cleared, the shared page is owned by VMM, TD attestation driver shouldn't reuse/free the pages. In the case of this driver, I think of two options - don't timeout. wait for interrupt to arrive and check the shared GPA state. - allow timeout. When the next request comes, check the shared GPA state. If it's still GET_QUOTE_IN_FLIGHT, return EBUSY. It's possible for VMM to keep the shared GPA forever maliciously(DoS) or unintentionally due to bug. TD can't do much about it. -- Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
