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

[David Gibson <david@gibson.dropbear.id.au>]

[-- Attachment #1: Type: text/plain, Size: 4368 bytes --]

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.

> +        /* 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.

> +        /* 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"

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]