[libvirt] [PATCH] tpm: Use /dev/null for cancel path if none was found

[Stefan Berger]

On 06/29/2017 02:06 PM, Daniel P. Berrange wrote:
> On Thu, Jun 29, 2017 at 02:01:11PM -0400, Stefan Berger wrote:
>> TPM 2 does not implement sysfs files for cancellation of commands.
>> We therefore use /dev/null for the cancel path passed to QEMU.
>>
>> Signed-off-by: Stefan Berger <stefanb at linux.vnet.ibm.com>
>> ---
>>   src/util/virtpm.c | 4 +---
>>   1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/src/util/virtpm.c b/src/util/virtpm.c
>> index 6d9b065..d5c10da 100644
>> --- a/src/util/virtpm.c
>> +++ b/src/util/virtpm.c
>> @@ -61,9 +61,7 @@ virTPMCreateCancelPath(const char *devpath)
>>                   VIR_FREE(path);
>>               }
>>               if (!path)
>> -                virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> -                               _("No usable sysfs TPM cancel file could be "
>> -                                 "found"));
>> +                ignore_value(VIR_STRDUP(path, "/dev/null"));
>>           } else {
>>               virReportError(VIR_ERR_INTERNAL_ERROR,
>>                              _("TPM device path %s is invalid"), devpath);
> It would be better to simply not set the cancel-path= argument to QEMU if
> it is not required / available.

Unfortunately QEMU will do the same thing as libvirt, that is search for 
the sysfs cancel path, unless it is provided via command line. We 
provide it here with a 'dummy path.'