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

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

[David Gibson]

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 <david@gibson.dropbear.id.au>
---
 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

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

[Stefan Berger]

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 {

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

[Jarkko Sakkinen]

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 <david@gibson.dropbear.id.au>
> ---
>  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