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Re: [tpmdd-devel] [PATCH v2 1/4] tpm: ignore burstcount to improve tpm_tis send() performance.

From Ken Goldman <kgold@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject Re: [tpmdd-devel] [PATCH v2 1/4] tpm: ignore burstcount to improve tpm_tis send() performance.
Date 2017-09-13 21:00 +0200
Message-ID <upl3b-2DF-1@gated-at.bofh.it> (permalink)
References <umI5X-1TZ-3@gated-at.bofh.it> <umI5X-1TZ-1@gated-at.bofh.it> <umLdw-4da-5@gated-at.bofh.it>
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On 9/6/2017 12:12 PM, Jason Gunthorpe wrote:
> 
> The problem with this approach is that the TPM could totally block
> the CPU for very long periods of time.
> 
> It seems very risky to enable..
> 

How would you characterize "very long"?

The TPM vendors confirm that they empty the FIFO at internal speeds that
are comparable to the bus speed.  Thus, any stall will be sub-usec.  Is
that an issue?

In addition, new TPMs have ever larger FIFO's, making stalls less likely
going forward.

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Re: [tpmdd-devel] [PATCH v2 1/4] tpm: ignore burstcount to improve  tpm_tis send() performance. Ken Goldman <kgold@linux.vnet.ibm.com> - 2017-09-13 21:00 +0200
  Re: [tpmdd-devel] [PATCH v2 1/4] tpm: ignore burstcount to improve tpm_tis send() performance. Peter Huewe <peterhuewe@gmx.de> - 2017-09-13 21:10 +0200

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