On Fri, Jul 02, 2021 at 12:16:12PM -0700, Hao Wu wrote: > > > On Jul 2, 2021, at 4:57 AM, Jarkko Sakkinen <jarkko@xxxxxxxxxx> wrote: > > > > On Fri, Jul 02, 2021 at 11:42:39AM +0300, Jarkko Sakkinen wrote: > >> On Fri, Jul 02, 2021 at 12:59:18AM -0700, Hao Wu wrote: > >>>> On Jul 2, 2021, at 12:45 AM, Jarkko Sakkinen <jarkko@xxxxxxxxxx> wrote: > >>>> > >>>> On Fri, Jul 02, 2021 at 12:33:15AM -0700, Hao Wu wrote: > >>>>> > >>>>> > >>>>>> On Jul 1, 2021, at 11:35 PM, Jarkko Sakkinen <jarkko@xxxxxxxxxx> wrote: > >>>>>> > >>>>>> On Tue, Jun 29, 2021 at 09:22:05PM -0700, Hao Wu wrote: > >>>>>>> This is a fix for the ATMEL TPM crash bug reported in > >>>>>>> https://patchwork.kernel.org/project/linux-integrity/patch/20200926223150.109645-1-hao.wu@xxxxxxxxxx/ > >>>>>>> > >>>>>>> According to the discussions in the original thread, > >>>>>>> we don't want to revert the timeout of wait_for_tpm_stat > >>>>>>> for non-ATMEL chips, which brings back the performance cost. > >>>>>>> For investigation and analysis of why wait_for_tpm_stat > >>>>>>> caused the issue, and how the regression was introduced, > >>>>>>> please read the original thread above. > >>>>>>> > >>>>>>> Thus the proposed fix here is to only revert the timeout > >>>>>>> for ATMEL chips by checking the vendor ID. > >>>>>>> > >>>>>>> Signed-off-by: Hao Wu <hao.wu@xxxxxxxxxx> > >>>>>>> Fixes: 9f3fc7bcddcb ("tpm: replace msleep() with usleep_range() in TPM 1.2/2.0 generic drivers") > >>>>>> > >>>>>> Fixes tag should be before SOB. > >>>>>> > >>>>>>> --- > >>>>>>> Test Plan: > >>>>>>> - Run fixed kernel with ATMEL TPM chips and see crash > >>>>>>> has been fixed. > >>>>>>> - Run fixed kernel with non-ATMEL TPM chips, and confirm > >>>>>>> the timeout has not been changed. > >>>>>>> > >>>>>>> drivers/char/tpm/tpm.h | 9 ++++++++- > >>>>>>> drivers/char/tpm/tpm_tis_core.c | 19 +++++++++++++++++-- > >>>>>>> include/linux/tpm.h | 2 ++ > >>>>>>> 3 files changed, 27 insertions(+), 3 deletions(-) > >>>>>>> > >>>>>>> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h > >>>>>>> index 283f78211c3a..bc6aa7f9e119 100644 > >>>>>>> --- a/drivers/char/tpm/tpm.h > >>>>>>> +++ b/drivers/char/tpm/tpm.h > >>>>>>> @@ -42,7 +42,9 @@ enum tpm_timeout { > >>>>>>> TPM_TIMEOUT_RANGE_US = 300, /* usecs */ > >>>>>>> TPM_TIMEOUT_POLL = 1, /* msecs */ > >>>>>>> TPM_TIMEOUT_USECS_MIN = 100, /* usecs */ > >>>>>>> - TPM_TIMEOUT_USECS_MAX = 500 /* usecs */ > >>>>>>> + TPM_TIMEOUT_USECS_MAX = 500, /* usecs */ > >>>>>> > >>>>>> What is this change? > >>>>> Need to add the tailing comma > >>>>> > >>>>>> > >>>>>>> + TPM_TIMEOUT_WAIT_STAT = 500, /* usecs */ > >>>>>>> + TPM_ATML_TIMEOUT_WAIT_STAT = 15000 /* usecs */ > >>>>>>> }; > >>>>>>> > >>>>>>> /* TPM addresses */ > >>>>>>> @@ -189,6 +191,11 @@ static inline void tpm_msleep(unsigned int delay_msec) > >>>>>>> delay_msec * 1000); > >>>>>>> }; > >>>>>>> > >>>>>>> +static inline void tpm_usleep(unsigned int delay_usec) > >>>>>>> +{ > >>>>>>> + usleep_range(delay_usec - TPM_TIMEOUT_RANGE_US, delay_usec); > >>>>>>> +}; > >>>>>> > >>>>>> Please remove this, and open code. > >>>>> Ok, will do > >>>>> > >>>>>>> + > >>>>>>> int tpm_chip_start(struct tpm_chip *chip); > >>>>>>> void tpm_chip_stop(struct tpm_chip *chip); > >>>>>>> struct tpm_chip *tpm_find_get_ops(struct tpm_chip *chip); > >>>>>>> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c > >>>>>>> index 55b9d3965ae1..9ddd4edfe1c2 100644 > >>>>>>> --- a/drivers/char/tpm/tpm_tis_core.c > >>>>>>> +++ b/drivers/char/tpm/tpm_tis_core.c > >>>>>>> @@ -80,8 +80,12 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask, > >>>>>>> } > >>>>>>> } else { > >>>>>>> do { > >>>>>>> - usleep_range(TPM_TIMEOUT_USECS_MIN, > >>>>>>> - TPM_TIMEOUT_USECS_MAX); > >>>>>>> + if (chip->timeout_wait_stat && > >>>>>>> + chip->timeout_wait_stat >= TPM_TIMEOUT_WAIT_STAT) { > >>>>>>> + tpm_usleep((unsigned int)(chip->timeout_wait_stat)); > >>>>>>> + } else { > >>>>>>> + tpm_usleep((unsigned int)(TPM_TIMEOUT_WAIT_STAT)); > >>>>>>> + } > >>>>>> > >>>>>> Invalid use of braces. Please read > >>>>>> > >>>>>> https://www.kernel.org/doc/html/v5.13/process/coding-style.html > >>>>>> > >>>>>> Why do you have to use this field conditionally anyway? Why doesn't > >>>>>> it always contain a legit value? > >>>>> The field is legit now, but doesn’t hurt to do addition check for robustness > >>>>> to ensure no crash ? Just in case the value is updated below TPM_TIMEOUT_WAIT_STAT ? > >>>>> > >>>>> Can remove if we think it is not needed. > >>>> > >>>> A simple question: why you use it conditionally? Can the field contain invalid value? > >>>> > >>> There are two checks > >>> - chip->timeout_wait_stat >= TPM_TIMEOUT_WAIT_STAT > >>> It could be invalid when future developer set it to some value less than `TPM_TIMEOUT_USECS_MIN`, > >>> and crash the usleep > >> > >> I don't understand this. Why you don't set to appropriate value? > Ok, fair enough, I assume developers will test it anyway to ensure no crash. Will remove this check. > > > What you should do, is to define two fields: > > > > - tpm_timeout_min > > - tpm_timeout_max > > > > And initialize these to TPM_TIMEOUT_USECS_MIN and TPM_TIMEOUT_USECS_MAX. > > > > Then fixup those for Atmel (with a simple if-statement, switch-case is > > overkill). > Switch was more for extensibility when other vendor has similar issue, > but we can refactor when needed in the future. I can use if-statement for now. Make things more fancy *only* when you actually need more fancy. > > The way you work out things right now is broken: > > > > 1. Before for non-Atmel: usleep_range(100, 500) > > 2. After for non-Atmel: usleep_range(200, 500) > I realized this in day-1, I think this range change does not matter much. By saying that you are actually saying that *undocumented* semantic changes to the kernel code are fine as long as they don't change things "too much" Are you serious about this? > `TPM_TIMEOUT_RANGE_US=300` is already used in the codebase, I assume people define > such if for general use cases for usleep_range in TPM > But we can add two fields if that makes us more comfortable to strictly follow the current code > semantically. This has absolutely nothing to do with "comfortable". It's black and white wrong. /Jarkko
