Re: [PATCH] tpm: Make timeout logic simpler and more robust

Mimi Zohar
2019-03-12T16:56:59Z

On Tue, 2019-03-12 at 14:36 +0200, Jarkko Sakkinen wrote:
> On Mon, Mar 11, 2019 at 04:54:04PM -0700, Calvin Owens wrote:
> > We're having lots of problems with TPM commands timing out, and we're
> > seeing these problems across lots of different hardware (both v1/v2).
> >
> > I instrumented the driver to collect latency data, but I wasn't able to
> > find any specific timeout to fix: it seems like many of them are too
> > aggressive. So I tried replacing all the timeout logic with a single
> > universal long timeout, and found that makes our TPMs 100% reliable.
> >
> > Given that this timeout logic is very complex, problematic, and appears
> > to serve no real purpose, I propose simply deleting all of it.
> >
> > Signed-off-by: Calvin Owens <calvinowens@fb.com>
>
> Have been thinking about this and I do agree. It has been like that
> before my times with this subsystem so when I did the original TPM2
> patches I carried this logic albeit even at that point I did not get it.
> Now that I've been maintaining for over three years I'm confident that
> this the Right Thing to do.

Please really consider this impact on IMA, before making this change.

Mimi