Re: [PATCH v4 3/8] tpm_emulator: Implement callback for whether we are suspended

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

On 12/12/19 1:33 PM, Stefan Berger wrote:
> On 12/12/19 1:07 PM, Stefan Berger wrote:
>> Implement the check whether the emulator backend is suspended.
>>
>> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
>>
>> diff --git a/hw/tpm/tpm_emulator.c b/hw/tpm/tpm_emulator.c
>> index 22f9113432..7be7d3a91b 100644
>> --- a/hw/tpm/tpm_emulator.c
>> +++ b/hw/tpm/tpm_emulator.c
>> @@ -80,6 +80,8 @@ typedef struct TPMEmulator {
>>       unsigned int established_flag_cached:1;
>>         TPMBlobBuffers state_blobs;
>> +
>> +    bool is_suspended;
>>   } TPMEmulator;
>>     struct tpm_error {
>> @@ -486,6 +488,13 @@ static size_t 
>> tpm_emulator_get_buffer_size(TPMBackend *tb)
>>       return actual_size;
>>   }
>>   +static bool tpm_emulator_is_suspended(TPMBackend *tb)
>> +{
>> +    TPMEmulator *tpm_emu = TPM_EMULATOR(tb);
>> +
>> +    return tpm_emu->is_suspended;
>> +}
>> +
>>   static int tpm_emulator_block_migration(TPMEmulator *tpm_emu)
>>   {
>>       Error *err = NULL;
>> @@ -846,6 +855,8 @@ static int tpm_emulator_pre_save(void *opaque)
>>       TPMBackend *tb = opaque;
>>       TPMEmulator *tpm_emu = TPM_EMULATOR(tb);
>>   +    tpm_emu->is_suspended = true;
>
> This is the most critical part here. It must be true when we receive a 
> response in the tpm_spapr_request_completed(). The problem is that 
> what tpm_backend_finish_sync() does is not specific to this backend 
> but more a global operation that another device could run as well -- 
> none seem to do this today. So the point is that there could be a race 
> here. This flag should really be set in '.pre_pre_save,' so before any 
> other device could poll. Better would be calling a global function 
> that indicates whether device suspension has started. In this case we 
> could do away with this and just call that function from the spapr 
> device.


runstate_check(RUN_STATE_FINISH_MIGRATE) seems to be what we need here...



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