Re: [PATCH v5 06/10] hw/tpm: Add support for VM migration with TPM CRB chunking

[Arun Menon <armenon@redhat.com>]

Hi,

On Wed, Apr 29, 2026 at 11:36:39AM -0400, Stefan Berger wrote:
> 
> 
> On 4/22/26 6:30 AM, Arun Menon wrote:
> > From: Arun Menon <armenon@redhat.com>
> > 
> > - Add subsection in VMState for TPM CRB with the newly introduced
> >    command and response buffer GByteArrays, along with a needed callback,
> >    so that newer QEMU only sends the buffers if it is necessary.
> > - Implement a migration blocker to prevent migration of the VM if the
> >    user manually enables chunking capability, cap-chunk, but the machine
> >    type does not support it, using a new hw_compat property called
> >    allow_chunk_migration.
> > - Add a post_load_errp hook so that during a migration, the buffers are
> >    validated before destination VM is started.
> > 
> > Signed-off-by: Arun Menon <armenon@redhat.com>
> > ---
> >   hw/core/machine.c |  1 +
> >   hw/tpm/tpm_crb.c  | 71 +++++++++++++++++++++++++++++++++++++++++++++++
> >   2 files changed, 72 insertions(+)
> > 
> > @@ -422,6 +478,7 @@ static void tpm_crb_reset(void *dev)
> >   static void tpm_crb_realize(DeviceState *dev, Error **errp)
> >   {
> >       CRBState *s = CRB(dev);
> > +    int ret;
> >       if (!tpm_find()) {
> >           error_setg(errp, "at most one TPM device is permitted");
> > @@ -431,6 +488,15 @@ static void tpm_crb_realize(DeviceState *dev, Error **errp)
> >           error_setg(errp, "'tpmdev' property is required");
> >           return;
> >       }
> > +    if (s->cap_chunk && !s->allow_chunk_migration) {
> > +        error_setg(&s->migration_blocker,
> > +                   "The tpm-crb device does not support chunk migration with "
> > +                   "machine version less than 11.1");
> > +        ret = migrate_add_blocker_normal(&s->migration_blocker, errp);
> > +        if (ret < 0) {
> > +            return;
> 
> Should this do an error_report() and exit(1)?

The tpm_crb_realize() function has always propagated errors in errp
back to the caller and returned in case of an error.
To be honest I followed the suit. A quick glance at the codebase shows
that the realize function in other devices also avoid calling exit().



Regards,
Arun Menon
> 
>