Messages in this thread | | | Date | Tue, 17 May 2022 13:08:26 -0700 | Subject | Re: [PATCH v6 5/5] x86/tdx: Add Quote generation support | From | Sathyanarayanan Kuppuswamy <> |
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On 5/16/22 7:58 PM, Kai Huang wrote: > On Fri, 2022-05-13 at 12:29 -0700, Sathyanarayanan Kuppuswamy wrote: >>> >>> >>>> + >>>> + /* Wait for attestation completion */ >>>> + ret = wait_for_completion_interruptible(&entry->compl); >>>> + if (ret < 0) { >>>> + /* >>>> + * For premature termination, since VMM still owns the >>>> + * shared buffer, mark the request invalid to let >>>> + * quote_callback_handler() handle the memory cleanup >>>> + * function. >>>> + */ >>>> + invalidate_quote_request(entry); >>> >>> Interrupt can arrive after signal interrupt. So invalidate_quote_request() >>> should check if the request is already processed, and return 0 or -EINTR. >>> Probably check the state always and del_list under single lock/unlock pair. >> >> Agree. But I think we should return -EINTR for the interrupted case >> irrespective of the processed status (so no return 0). >> >> I will hold the lock and handle the cleanup for the processed >> status. > > Even if we check the buffer status in invalidate_quote_request(), there's no > guarantee the VMM won't change the buffer status _after_ we do the check, so > looks such check isn't necessary. >
Consider the case where we get a callback interrupt, and before we complete the processing for it, user terminates the request. In this scenario, quote_callback_handler() will consider the request is still valid and no do the memory cleanup. To handle this case, we need to check the status in invalidate_quote_request() and do the cleanup if required.
/* Handles early termination of GetQuote requests */ void invalidate_quote_request(struct quote_entry *entry) { struct tdx_quote_hdr *quote_hdr;
/* * For early termination, if the request is not yet * processed by VMM (GET_QUOTE_IN_FLIGHT), the VMM * still owns the shared buffer, so mark the request * invalid to let quote_callback_handler() handle the * memory cleanup function. If the request is already * processed, then do the cleanup and return. */
mutex_lock("e_lock); quote_hdr = (struct tdx_quote_hdr *)entry->buf->vmaddr; if (quote_hdr->status == GET_QUOTE_IN_FLIGHT) { entry->valid = false; mutex_unlock("e_lock); return; } _del_quote_entry(entry); mutex_unlock("e_lock); }
-- Sathyanarayanan Kuppuswamy Linux Kernel Developer
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