On Sat, Nov 11, 2017 at 01:31:32PM -0700, Jerry Snitselaar wrote: > On Sat Nov 11 17, Jason Gunthorpe wrote: > > On Sat, Nov 11, 2017 at 12:12:57PM -0700, Jerry Snitselaar wrote: > > > > > Before the release_locality code would only actually release the > > > locality if the request use bit was set. So after it grabbed the > > > locality during probe it probably never released it. The idea with the > > > new code was to release it when it was no longer needed so another > > > requester would be able to take the tpm without having to wait for it > > > to be released. > > > > If I recall, this was so that system level things outside linux could > > access the TPM properly?? > > > > Yes, that is what drove this initially. I believe Jarkko was also > thinking of the possibility in the future where something like a vm > could request a locality as well, but that is just a hazy recollection > of emails from back then. This was something I recall discussing in LPC 2016 in the hallway at least :-) A tidbit but it could make sense to tie it to VMM, not VM. > > > > With the old code I think it would have to wait either > > > until the next time release_locality was called, or attempt to seize > > > the tpm with the seize bit in the access register. I need to read > > > through the spec some more, but does the tpm ever force a change when > > > the request use bit is set, or does it leave it up to the software > > > to deal with it and only gets involved in the case where the seize > > > bit has been set? > > > > Do we handle these cases? Maybe something like that has happened.. > > > > Jason > > If that is what happened in this case we should see the beenSeized bit > set in the access register (assuming the chip is doing things properly), > but it only had the tpmRegValidSts and tpmEstablishment bits set. > > There is code in the interrupt handling that notices if the locality > changes if the chip has that capability, but I don't think there is > anything that deals with the seize bit. Another thing to be looked > at. For me it is hard to understand who is the 3rd party who would be using other locality and accessing TPM after OS handover in the regression in question. /Jarkko
