On 06/19/2018 06:10 AM, Jarkko Sakkinen wrote: > On Tue, Jun 12, 2018 at 10:58:26AM -0700, Tadeusz Struk wrote: >> The TCG SAPI specification [1] defines a set of functions, which allows >> applications to use the TPM device in either blocking or non-blocking fashion. >> Each command defined by the specification has a corresponding >> Tss2_Sys_<COMMAND>_Prepare() and Tss2_Sys_<COMMAND>_Complete() call, which >> together with Tss2_Sys_ExecuteAsync() is designed to allow asynchronous >> mode of operation. Currently the TPM driver supports only blocking calls, >> which doesn't allow asynchronous IO operations. >> This patch changes it and adds support for nonblocking write and a new poll >> function to enable applications, which want to take advantage of this feature. >> The new functionality can be tested using standard TPM tools implemented >> in [2], together with modified TCTI from [3]. >> >> [1] https://trustedcomputinggroup.org/wp-content/uploads/TSS_SAPI_Version-1.1_Revision-22_review_030918.pdf >> [2] https://github.com/tpm2-software/tpm2-tools >> [3] https://github.com/tstruk/tpm2-tss/tree/async > > For me the value is still a bit questionable. The benchmark looks a bit > flakky to give much figures how this would work with real world workloads. > > I read James response and I also have to question why not just a worker > thread in user space? TPM does only one command at a time anyways. > > Cannot take this in before I know that user space will (1) adapt to > this and (2) gain value compared to a worker thread. > Hi Jarkko, Thanks for reviewing the patch. There are applications/frameworks where a worker thread is not an option. Take for example the IoT use-cases and frameworks like IoT.js, or "Node.js for IoT". They are all single threaded, event-driven frameworks, using non-blocking I/O as the base of their processing model. Similarly embedded applications, which are basically just a single threaded event loop, quite often don't use threads because of resources constrains. If your concern is that user space will not adopt to this, I can say that TSS library [1] is currently blocked on this feature, and we can not enable some of the use-cases mentioned above because of this. Thanks, Tadeusz [1] https://github.com/tpm2-software/tpm2-tss
