2020-06-19 03:41:24

by David Gibson

Subject: [PATCHv2] tpm: ibmvtpm: Wait for ready buffer before probing for TPM2 attributes

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 <[email protected]>
---

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

2020-06-19 04:37:13

by Jerry Snitselaar

Subject: Re: [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 <[email protected]>
>---

Reviewed-by: Jerry Snitselaar <[email protected]>

>
>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
>

2020-06-23 00:51:06

by Jarkko Sakkinen

Subject: Re: [PATCHv2] tpm: ibmvtpm: Wait for ready buffer before probing for TPM2 attributes

On Fri, Jun 19, 2020 at 01:30:40PM +1000, 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 <[email protected]>

Reviewed-by: Jarkko Sakkinen <[email protected]>

/Jarkko