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

[Stefan Berger]

On 1/17/20 8:31 AM, Marc-André Lureau wrote:
> Hi
>
> On Wed, Jan 8, 2020 at 8:14 PM Stefan Berger <address@hidden> wrote:
> > From: Stefan Berger <address@hidden>
> >
> > Extend the tpm_spapr frontend with VM suspend and resume support.
> >
> > Signed-off-by: Stefan Berger <address@hidden>
> > ---
> >   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.