Re: [PATCH v5 3/5] tpm_spapr: Support suspend and resume

[Stefan Berger <stefanb@linux.ibm.com>]

On 12/13/19 12:39 AM, David Gibson wrote:
> On Thu, Dec 12, 2019 at 03:24:28PM -0500, Stefan Berger wrote:
>> Extend the tpm_spapr frontend with VM suspend and resume support.
>>
>> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
>>
>> diff --git a/hw/tpm/tpm_spapr.c b/hw/tpm/tpm_spapr.c
>> index c4a67e2403..8f5a142bd4 100644
>> --- a/hw/tpm/tpm_spapr.c
>> +++ b/hw/tpm/tpm_spapr.c
>> @@ -87,6 +87,8 @@ typedef struct {
>>       TPMVersion be_tpm_version;
>>   
>>       size_t be_buffer_size;
>> +
>> +    bool deliver_response; /* whether to deliver response after VM resume */
>>   } SPAPRvTPMState;
>>   
>>   static void tpm_spapr_show_buffer(const unsigned char *buffer,
>> @@ -256,6 +258,12 @@ static void tpm_spapr_request_completed(TPMIf *ti, int ret)
>>       uint32_t len;
>>       int rc;
>>   
>> +    if (runstate_check(RUN_STATE_FINISH_MIGRATE)) {
> I'm trying to figure out the circumstances in which
> request_completed() would get called before post_load on the
> destination.


This is on the source side where we must not deliver the response in 
case the devices are now suspending but defer the delivery to after the 
resume.


>
>> +        /* defer delivery of response until .post_load */
>> +        s->deliver_response |= true;
> |= is a bitwise OR which is not what you want, although it will
> *probably* work in practice.  Better to just use
> 	s->deliver_response = true;
>
>> +        return;
>> +    }
>> +
>>       s->state = SPAPR_VTPM_STATE_COMPLETION;
>>   
>>       /* a max. of be_buffer_size bytes can be transported */
>> @@ -316,6 +324,7 @@ static void tpm_spapr_reset(SpaprVioDevice *dev)
>>       SPAPRvTPMState *s = VIO_SPAPR_VTPM(dev);
>>   
>>       s->state = SPAPR_VTPM_STATE_NONE;
>> +    s->deliver_response = false;
>>   
>>       s->be_tpm_version = tpm_backend_get_tpm_version(s->be_driver);
>>       tpm_spapr_update_deviceclass(dev);
>> @@ -339,9 +348,53 @@ static enum TPMVersion tpm_spapr_get_version(TPMIf *ti)
>>       return tpm_backend_get_tpm_version(s->be_driver);
>>   }
>>   
>> +/* persistent state handling */
>> +
>> +static int tpm_spapr_pre_save(void *opaque)
>> +{
>> +    SPAPRvTPMState *s = opaque;
>> +
>> +    s->deliver_response |= tpm_backend_finish_sync(s->be_driver);
> Same problem here.
>
>> +    trace_tpm_spapr_pre_save(s->deliver_response);
>> +    /*
>> +     * we cannot deliver the results to the VM since DMA would touch VM memory
>> +     */
>> +
>> +    return 0;
>> +}
>> +
>> +static int tpm_spapr_post_load(void *opaque, int version_id)
>> +{
>> +    SPAPRvTPMState *s = opaque;
>> +
>> +    if (s->deliver_response) {
>> +        trace_tpm_spapr_post_load();
>> +        /* deliver the results to the VM via DMA */
>> +        tpm_spapr_request_completed(TPM_IF(s), 0);
>> +        s->deliver_response = false;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>>   static const VMStateDescription vmstate_spapr_vtpm = {
>>       .name = "tpm-spapr",
>> -    .unmigratable = 1,
>> +    .version_id = 1,
>> +    .minimum_version_id = 0,
>> +    .minimum_version_id_old = 0,
>> +    .pre_save = tpm_spapr_pre_save,
>> +    .post_load = tpm_spapr_post_load,
>> +    .fields = (VMStateField[]) {
>> +        VMSTATE_SPAPR_VIO(vdev, SPAPRvTPMState),
>> +
>> +        VMSTATE_UINT8(state, SPAPRvTPMState),
>> +        VMSTATE_BUFFER(buffer, SPAPRvTPMState),
> Transferring the whole 4kiB buffer unconditionally when it mostly
> won't have anything useful in it doesn't seem like a great idea.


It's really only needed in case of a 'delayed response'. So, yeah, we 
could transfer data in only that case then.


>
>> +        /* remember DMA address */
>> +        VMSTATE_UINT32(crq.s.data, SPAPRvTPMState),
>> +        VMSTATE_BOOL(deliver_response, SPAPRvTPMState),
>> +        VMSTATE_END_OF_LIST(),
>> +    }
>>   };
>>   
>>   static Property tpm_spapr_properties[] = {
>> diff --git a/hw/tpm/trace-events b/hw/tpm/trace-events
>> index 6278a39618..d109661b96 100644
>> --- a/hw/tpm/trace-events
>> +++ b/hw/tpm/trace-events
>> @@ -67,3 +67,5 @@ tpm_spapr_do_crq_get_version(uint32_t version) "response: version %u"
>>   tpm_spapr_do_crq_prepare_to_suspend(void) "response: preparing to suspend"
>>   tpm_spapr_do_crq_unknown_msg_type(uint8_t type) "Unknown message type 0x%02x"
>>   tpm_spapr_do_crq_unknown_crq(uint8_t raw1, uint8_t raw2) "unknown CRQ 0x%02x 0x%02x ..."
>> +tpm_spapr_pre_save(bool v) "TPM response to deliver after resume: %d"
>> +tpm_spapr_post_load(void) "Delivering TPM response after resume"