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SubjectRe: [PATCH] tpm: ibmvtpm: Wait for ready buffer before probing for TPM2 attributes
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On 6/5/20 2:37 AM, David Gibson wrote:
> The tpm2_get_cc_attrs_tbl() call will result in TPM commands being issued,
> which will need the use of the internal command/response buffer. But,
> we're issuing this *before* we've waited to make sure that buffer is
> allocated.
>
> This can result in intermittent failures to probe if the hypervisor / TPM
> implementation doesn't respond quickly enough. I find it fails almost
> every time with an 8 vcpu guest under KVM with software emulated TPM.

Uuuh. Thanks!


> Fixes: 18b3670d79ae9 "tpm: ibmvtpm: Add support for TPM2"
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>



> ---
> drivers/char/tpm/tpm_ibmvtpm.c | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_ibmvtpm.c b/drivers/char/tpm/tpm_ibmvtpm.c
> index 09fe45246b8c..994385bf37c0 100644
> --- a/drivers/char/tpm/tpm_ibmvtpm.c
> +++ b/drivers/char/tpm/tpm_ibmvtpm.c
> @@ -683,13 +683,6 @@ static int tpm_ibmvtpm_probe(struct vio_dev *vio_dev,
> if (rc)
> goto init_irq_cleanup;
>
> - if (!strcmp(id->compat, "IBM,vtpm20")) {
> - chip->flags |= TPM_CHIP_FLAG_TPM2;
> - rc = tpm2_get_cc_attrs_tbl(chip);
> - if (rc)
> - goto init_irq_cleanup;
> - }
> -
> if (!wait_event_timeout(ibmvtpm->crq_queue.wq,
> ibmvtpm->rtce_buf != NULL,
> HZ)) {
> @@ -697,6 +690,13 @@ static int tpm_ibmvtpm_probe(struct vio_dev *vio_dev,
> goto init_irq_cleanup;
> }
>
> + if (!strcmp(id->compat, "IBM,vtpm20")) {
> + chip->flags |= TPM_CHIP_FLAG_TPM2;
> + rc = tpm2_get_cc_attrs_tbl(chip);
> + if (rc)
> + goto init_irq_cleanup;
> + }
> +
> return tpm_chip_register(chip);
> init_irq_cleanup:
> do {



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