Re: [PATCH v8 4/6] tpm_spapr: Support suspend and resume

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

On 1/17/20 8:31 AM, Marc-André Lureau wrote:
> Hi
>
> On Wed, Jan 8, 2020 at 8:14 PM Stefan Berger <stefanb@linux.ibm.com> wrote:
>> From: Stefan Berger <stefanb@linux.vnet.ibm.com>
>>
>> Extend the tpm_spapr frontend with VM suspend and resume support.
>>
>> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
>> ---
>>   hw/tpm/tpm_spapr.c  | 67 ++++++++++++++++++++++++++++++++++++++++++++-
>>   hw/tpm/trace-events |  2 ++
>>   2 files changed, 68 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/tpm/tpm_spapr.c b/hw/tpm/tpm_spapr.c
>> index ab184fbb82..cf5c7851e7 100644
>> --- a/hw/tpm/tpm_spapr.c
>> +++ b/hw/tpm/tpm_spapr.c
>> @@ -76,6 +76,9 @@ typedef struct {
>>
>>       unsigned char buffer[TPM_SPAPR_BUFFER_MAX];
>>
>> +    uint32_t numbytes; /* number of bytes in suspend_buffer */
>> +    unsigned char *suspend_buffer;
> Why do you need a copy suspend_buffer? Why not use and save buffer[] directly?


This addresses David's comment:

"Transferring the whole 4kiB buffer unconditionally when it mostly
won't have anything useful in it doesn't seem like a great idea."

https://lists.nongnu.org/archive/html/qemu-devel/2019-12/msg02601.html


>
> Also numbytes wouldn't be necessary, you would just need a bool flag
> to say if the request_completed is pending.
>
>> +
>>       TPMBackendCmd cmd;
>>
>>       TPMBackend *be_driver;
>> @@ -240,6 +243,13 @@ static void tpm_spapr_request_completed(TPMIf *ti, int ret)
>>
>>       /* a max. of be_buffer_size bytes can be transported */
>>       len = MIN(tpm_cmd_get_size(s->buffer), s->be_buffer_size);
>> +
>> +    if (runstate_check(RUN_STATE_FINISH_MIGRATE)) {
>> +        /* defer delivery of response until .post_load */
>> +        s->numbytes = len;
>> +        return;
>> +    }
>> +
>>       rc = spapr_vio_dma_write(&s->vdev, be32_to_cpu(crq->data),
>>                                s->buffer, len);
>>
>> @@ -288,11 +298,13 @@ static void tpm_spapr_reset(SpaprVioDevice *dev)
>>       SpaprTpmState *s = VIO_SPAPR_VTPM(dev);
>>
>>       s->state = SPAPR_VTPM_STATE_NONE;
>> +    s->numbytes = 0;
>>
>>       s->be_tpm_version = tpm_backend_get_tpm_version(s->be_driver);
>>
>>       s->be_buffer_size = MIN(tpm_backend_get_buffer_size(s->be_driver),
>>                               TPM_SPAPR_BUFFER_MAX);
>> +    s->suspend_buffer = g_realloc(s->suspend_buffer, s->be_buffer_size);
>>
>>       tpm_backend_reset(s->be_driver);
>>       tpm_spapr_do_startup_tpm(s, s->be_buffer_size);
>> @@ -309,9 +321,62 @@ 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)
>> +{
>> +    SpaprTpmState *s = opaque;
>> +
>> +    tpm_backend_finish_sync(s->be_driver);
>> +
>> +    if (s->numbytes) {
>> +        memcpy(s->suspend_buffer, s->buffer, s->numbytes);
>> +    }
>> +
>> +    trace_tpm_spapr_pre_save(s->numbytes);
>> +    /*
>> +     * 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)
>> +{
>> +    SpaprTpmState *s = opaque;
>> +
>> +    if (s->numbytes) {
>> +        trace_tpm_spapr_post_load();
>> +
>> +        memcpy(s->buffer, s->suspend_buffer,
>> +               MIN(s->numbytes, s->be_buffer_size));
>> +        /* deliver the results to the VM via DMA */
>> +        tpm_spapr_request_completed(TPM_IF(s), 0);
>> +        s->numbytes = 0;
>> +    }
>> +
>> +    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,
>
> Yyou should leave all the fields to 0 (there is no version 0 so far).
> Thus no need to have them set explicitly either.


Ok, I will fix.

   Thanks.