Re: TPM selftest failure in 4.15

Jason Gunthorpe
2018-02-01T20:36:01Z

On Thu, Feb 01, 2018 at 09:00:04PM +0100, James Bottomley wrote:
> On Thu, 2018-02-01 at 11:59 -0700, Jason Gunthorpe wrote:
> > On Thu, Feb 01, 2018 at 07:46:04PM +0100, James Bottomley wrote:
> >
> > >
> > > I honestly don't think we should be waiting for the self test at
> > > all.
> > > We should kick it off and treat any TPM_RC_TESTING error as
> > > -EAGAIN.
> > > We're already under fire for slow boot sequences and adding 2s just
> > > to
> > > wait for the TPM to self test adds to that for no real value.
> >
> > Arguably the BIOS should have completed the selftest - this stuff
> > generally only exists to support embedded.
> >
> > I don't like the idea of EAGAIN, that just expose all our users to
> > this mess.
> >
> > I would support making transmit_cmd genericly wait and retry if the
> > TPM insists we need to wait for selftest to complete the specific
> > command though.
>
> OK, how about this then?

Yeah, I like this concept much better, thanks

> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index 1d6729be4cd6..84ed271c060b 100644
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -521,12 +521,32 @@ ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_space *space,
> const struct tpm_output_header *header = buf;
> int err;
> ssize_t len;
> + unsigned int delay_msec = 20;
>
> - len = tpm_transmit(chip, space, (u8 *)buf, bufsiz, flags);
> - if (len < 0)
> - return len;
> + /*
> + * on first probe we kick off a TPM self test in the
> + * background This means the TPM may return RC_TESTING to any
> + * command that tries to use a subsystem under test, so do an
> + * exponential backoff wait if that happens
> + */
> + for (;;) {
> + len = tpm_transmit(chip, space, (u8 *)buf, bufsiz, flags);
> + if (len < 0)
> + return len;
> +
> + err = be32_to_cpu(header->return_code);
> + if (err != TPM2_RC_TESTING ||
> + (flags & TPM_TRANSMIT_NOWAIT))
> + break;

Do TPM and TPM2 use a different return code here?

Jason