On Fri, Oct 16, 2020 at 11:11:37PM -0700, Hao Wu wrote: > > On Oct 1, 2020, at 4:04 PM, Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote: > > > > On Thu, Oct 01, 2020 at 11:32:59AM -0700, James Bottomley wrote: > >> On Thu, 2020-10-01 at 14:15 -0400, Nayna wrote: > >>> On 10/1/20 12:53 AM, James Bottomley wrote: > >>>> On Thu, 2020-10-01 at 04:50 +0300, Jarkko Sakkinen wrote: > >>>>> On Wed, Sep 30, 2020 at 03:31:20PM -0700, James Bottomley wrote: > >>>>>> On Thu, 2020-10-01 at 00:09 +0300, Jarkko Sakkinen wrote: > >> [...] > >>>>>>> I also wonder if we could adjust the frequency dynamically. > >>>>>>> I.e. start with optimistic value and lower it until finding > >>>>>>> the sweet spot. > >>>>>> > >>>>>> The problem is the way this crashes: the TPM seems to be > >>>>>> unrecoverable. If it were recoverable without a hard reset of > >>>>>> the entire machine, we could certainly play around with it. I > >>>>>> can try alternative mechanisms to see if anything's viable, but > >>>>>> to all intents and purposes, it looks like my TPM simply stops > >>>>>> responding to the TIS interface. > >>>>> > >>>>> A quickly scraped idea probably with some holes in it but I was > >>>>> thinking something like > >>>>> > >>>>> 1. Initially set slow value for latency, this could be the > >>>>> original 15 ms. > >>>>> 2. Use this to read TPM_PT_VENDOR_STRING_*. > >>>>> 3. Lookup based vendor string from a fixup table a latency that > >>>>> works > >>>>> (the fallback latency could be the existing latency). > >>>> > >>>> Well, yes, that was sort of what I was thinking of doing for the > >>>> Atmel ... except I was thinking of using the TIS VID (16 byte > >>>> assigned vendor ID) which means we can get the information to set > >>>> the timeout before we have to do any TPM operations. > >>> > >>> I wonder if the timeout issue exists for all TPM commands for the > >>> same manufacturer. For example, does the ATMEL TPM also crash when > >>> extending PCRs ? > >>> > >>> In addition to defining a per TPM vendor based lookup table for > >>> timeout, would it be a good idea to also define a Kconfig/boot param > >>> option to allow timeout setting. This will enable to set the timeout > >>> based on the specific use. > >> > >> I don't think we need go that far (yet). The timing change has been in > >> upstream since: > >> > >> commit 424eaf910c329ab06ad03a527ef45dcf6a328f00 > >> Author: Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx> > >> Date: Wed May 16 01:51:25 2018 -0400 > >> > >> tpm: reduce polling time to usecs for even finer granularity > >> > >> Which was in the released kernel 4.18: over two years ago. In all that > >> time we've discovered two problems: mine which looks to be an artifact > >> of an experimental upgrade process in a new nuvoton and the Atmel. > >> That means pretty much every other TPM simply works with the existing > >> timings > >> > >>> I was also thinking how will we decide the lookup table values for > >>> each vendor ? > >> > >> I wasn't thinking we would. I was thinking I'd do a simple exception > >> for the Atmel and nothing else. I don't think my Nuvoton is in any way > >> characteristic. Indeed my pluggable TPM rainbow bridge system works > >> just fine with a Nuvoton and the current timings. > >> > >> We can add additional exceptions if they actually turn up. > > > > I'd add a table and fallback. > > > > Hi folks, > > I want to follow up this a bit and check whether we reached a consensus > on how to fix the timeout issue for Atmel chip. > > Should we revert the changes or introduce the lookup table for chips. > > Is there anything I can help from Rubrik side. > > Thanks > Hao There is nothing to revert as the previous was not applied but I'm of course ready to review any new attempts. /Jarkko
