On Fri, Nov 13, 2020 at 08:39:28PM -0800, Hao Wu wrote: > > On Oct 17, 2020, at 10:20 PM, Hao Wu <hao.wu@xxxxxxxxxx> wrote: > > > >> On Oct 17, 2020, at 10:09 PM, Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote: > >> > >> 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. > >> > > > > Hi Jarkko, > > > > By “revert” I meant we revert the timeout value changes by applying > > the patch I proposed, as the timeout value discussed does cause issues. > > > > Why don’t we apply the patch and improve the perf in the way of not > > breaking TPMs ? > > > > Hao > > Hi Jarkko and folks, > > It’s being a while since our last discussion. I want to push a fix in the upstream for ateml chip. > It looks like we currently have following choices: > 1. generic fix for all vendors: have a lookup table for sleep time of wait_for_tpm_stat > (i.e. TPM_TIMEOUT_WAIT_STAT in my proposed patch) > 2. quick fix for the regression: change the sleep time of wait_for_tpm_stat back to 15ms. > It is the current proposed patch > 3. Fix regression by making exception for ateml chip. > > Should we reach consensus on which one we want to pursue before dig > into implementation of the patch? In my opinion, I prefer to fix the > regression with 2, and then pursue 1 as long-term solution. 3 is > hacky. What does option 1 fix for *all* vendors? > Let me know what do you guys think > > Hao /Jarkko
