2020-06-05 06:44:32

by David Gibson

Subject: [PATCH] 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.

Fixes: 18b3670d79ae9 "tpm: ibmvtpm: Add support for TPM2"
Signed-off-by: David Gibson <[email protected]>
---
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 {
--
2.26.2

2020-06-05 15:36:09

by Stefan Berger

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

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 <[email protected]>
Reviewed-by: Stefan Berger <[email protected]>



> ---
> 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 {

2020-06-16 21:16:40

by Jarkko Sakkinen

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

On Fri, Jun 05, 2020 at 04:37:19PM +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.
>
> Fixes: 18b3670d79ae9 "tpm: ibmvtpm: Add support for TPM2"

Should be Fixes: 18b3670d79ae ("tpm: ibmvtpm: Add support for TPM2")

Also briefly state what the commit does, not just the problem
description. The code change looks legit.

Please send v2 with these changes.

> Signed-off-by: David Gibson <[email protected]>
> ---
> 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 {
> --
> 2.26.2
>

/Jarkko