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

[Marc-André Lureau]

On Fri, Jan 17, 2020 at 5:41 PM Stefan Berger <address@hidden> wrote:
>
> 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

Oh ok.. (well really I don't think 4k (usually compressed) will really
matter much in multi-gigabytes streams ;)

>
>
> >
> > 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.



-- 
Marc-André Lureau