On Tue, Jan 17, 2017 at 09:58:27AM -0800, Andrey Pronin wrote: > > Yes, sorry, I should have mentioned that.. Maybe that is too much to > > fix.. > > If we fix sysfs to go through tpm_try_get_ops, then all we can do for > shutdown is indeed something like
Maybe yes, I also had at one point a thought to push the read side of the ops_sem all the way down to the transmit_cmd level... But that complicates calling shutdown. > down_write(&chip->ops_sem); > if (chip->ops && chip->flags & TPM_CHIP_FLAG_TPM2) > tpm2_shutdown(chip, TPM2_SU_CLEAR); > chip->ops = NULL; > up_write(&chip->ops_sem); > > Does that sound like a good plan? > If we don't want sysfs to increment/decrement the reference count for > the device, we can still make it go through Grabbing the extra kref is harmless.. > > I'm confused - doesn't your system reset the TPM when it reboots? > > Isn't that required so the firmware starts with known PCRs? Doesn't > > reset trump unorderly shutdown? > > > > That's right, the TPM is reset when the system reboots. However, for > TPM 2.0, if it resets w/o Shutdown(CLEAR) first, it will detect it > during Startup, and mark as unorderly shutdown. Shutdown(CLEAR) is > the signal to the TPM to save its state to nvram and prepare to reset. > If it was not done, it is possible that something was not saved (e.g. > the DA counter), and the chip correctly marks it as a potential DA > problem. Okay, that makes sense, and needs to go in a comment someplace! > > > All these things are handled by tpm_chip_unregister(). I thought about > > > creating a tpm_chip_shutdown routine that could be called from shutdown > > > handlers of the drivers that need it (and I'd do it for every driver, > > > especially in 2.0 case). But decided that it's better to reuse the > > > existing tpm_chip_unregister() that already does what's needed. > > > > If for some reason we need this for every driver then this is probably > > a better approach - but that seems very, very strange to me. > > As described above, we can do a smaller tpm_chip_shutdown() that the > drivers that need it (2.0 or susceptible to issues if reset in the > middle of command) can call. > I'll do it, if it sounds like the right plan to you. Yes please.. Is there some way we can have the TPM core do this without requiring the driver to add a shutdown the struct driver? Maybe we could put something in chip->dev->driver? Not sure.. Jason
