Re: [Qemu-devel] [RFC PATCH v1 5/6] spapr: Unregister HPT savevm handlers for radix guests

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

On Wed, May 17, 2017 at 04:59:33PM +1000, David Gibson wrote:
> On Wed, May 17, 2017 at 09:19:21AM +0530, Bharata B Rao wrote:
> > HPT gets created by default and later when the guest turns out to be
> > a radix guest, the HPT is destroyed when guest does H_REGISTER_PROC_TBL
> > hcall.
> 
> I don't think that's entirely accurate.  At least in some KVM
> configurations, we assume radix first, and only allocate the HPT once
> the guest confirms it is doing hash.

Right, that statement is true for TCG radix guests, will rephrase it.

> 
> > Let HTAB savevm handlers registration and unregistration follow
> > the same model so that we don't end up having unrequired HTAB savevm
> > handlers for radix guests.
> > 
> > This also ensures that HTAB savevm handlers seemlessly get destroyed and
> > recreated like HTAB itself when hash guest reboots.
> > 
> > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> > ---
> >  hw/ppc/spapr.c         | 15 +++++++++++++--
> >  hw/ppc/spapr_hcall.c   |  1 +
> >  include/hw/ppc/spapr.h |  2 ++
> >  3 files changed, 16 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index 521eef1..05abfc1 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -1237,6 +1237,7 @@ static void spapr_reallocate_hpt(sPAPRMachineState *spapr, int shift,
> >  
> >      /* Clean up any HPT info from a previous boot */
> >      spapr_free_hpt(spapr);
> > +    spapr_htab_savevm_unregister(spapr);
> 
> I'd prefer that the unregister be folded into spapr_free_hpt().
> Basically we want calls that create or remove the HPT and handle
> everything - allocation/freeing if necessary, informing KVM if
> necessary, and registering/deregistering the savevm handlers if
> necesary.
> 
> I think that will also remove the need for the trivial
> spapr_htab_savevm_{un,}register() wrappers.

Sure, will consolidate this in the next version.

Regards,
Bharata.