Re: [Xen-devel] [PATCH] vTPM: Fix Atmel timeout bug.

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 30/10/14 13:05, Emil Condrea wrote:
> Some versions of Atmel TPMs provide invalid values for 
> TPM_CAP_PROP_TIS_TIMEOUT query.
> Because timeouts are invalid, every other command after tpm_get_timeouts will 
> fail.
> It is a known issue and it was fixed recently in linux kernel tpm_tis.c on 
> 2014-07-29.
> This patch does not allow timeouts to be less than standard values.
> I tested it on a Dell Latitude E5520 and after making the changes I was able 
> to start vtpmmgr-stubdom.
>
> Signed-off-by: Emil Condrea <emilcondrea@xxxxxxxxx>
> ---
>  extras/mini-os/tpm_tis.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/extras/mini-os/tpm_tis.c b/extras/mini-os/tpm_tis.c
> index b067cb7..81d426a 100644
> --- a/extras/mini-os/tpm_tis.c
> +++ b/extras/mini-os/tpm_tis.c
> @@ -33,6 +33,11 @@
>  #ifndef min
>       #define min( a, b ) ( ((a) < (b)) ? (a) : (b) )
>  #endif
> +#define ADJUST_TIMEOUTS_TO_STANDARD(initial,standard,timeout_no)             
>         \
> +     if((initial) < (standard)){                                             
>         \
> +             (initial) = (standard);                                         
>         \
> +             printk("Timeout %c was adjusted to standard 
> value.\n",timeout_no);      \
> +     }
>  
>  #define TPM_HEADER_SIZE 10
>  
> @@ -997,15 +1002,22 @@ int tpm_get_timeouts(struct tpm_chip *chip)
>     }
>     if (timeout)
>        chip->timeout_a = MICROSECS(timeout * scale); /*Convert to msec */
> +   
> ADJUST_TIMEOUTS_TO_STANDARD(chip->timeout_a,MILLISECS(TIS_SHORT_TIMEOUT),'a');

Surely each of these are just

chip->timeout_a = max(MICROSECS(timeout * scale),
MILLISECS(TIS_SHORT_TIMEOUT))

Also, are you certain that the units here are correct?  The micro vs
milli seconds looks odd.

~Andrew


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