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SubjectRe: [PATCHv2] tpm: ibmvtpm: Wait for ready buffer before probing for TPM2 attributes
On Fri Jun 19 20, 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.
>
>To fix it, just move the tpm2_get_cc_attrs_tlb() call after the
>existing code to wait for initialization, which will ensure the buffer
>is allocated.
>
>Fixes: 18b3670d79ae9 ("tpm: ibmvtpm: Add support for TPM2")
>Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
>---

Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>

>
>Changes from v1:
> * Fixed a formatting error in the commit message
> * Added some more detail to the commit message
>
>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 09fe45246b8cc..994385bf37c0c 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 {
>--
>2.26.2
>

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