Re: [Qemu-devel] [RFC PATCH v1 6/6] spapr: Fix migration of Radix guests

[Bharata B Rao]

On Wed, May 17, 2017 at 05:20:31PM +1000, David Gibson wrote:
> On Wed, May 17, 2017 at 12:45:39PM +0530, Bharata B Rao wrote:
> > On Wed, May 17, 2017 at 05:00:49PM +1000, David Gibson wrote:
> > > On Wed, May 17, 2017 at 09:19:22AM +0530, Bharata B Rao wrote:
> > > > Fix migration of radix guests by ensuring that we issue
> > > > KVM_PPC_CONFIGURE_V3_MMU for radix case post migration.
> > > > 
> > > > Reported-by: Nageswara R Sastry <address@hidden>
> > > > Signed-off-by: Bharata B Rao <address@hidden>
> > > > ---
> > > >  hw/ppc/spapr.c         | 15 +++++++++++++++
> > > >  hw/ppc/spapr_hcall.c   |  1 +
> > > >  include/hw/ppc/spapr.h |  1 +
> > > >  3 files changed, 17 insertions(+)
> > > > 
> > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > > index 05abfc1..dd1d687 100644
> > > > --- a/hw/ppc/spapr.c
> > > > +++ b/hw/ppc/spapr.c
> > > > @@ -1443,6 +1443,20 @@ static int spapr_post_load(void *opaque, int 
> > > > version_id)
> > > >          err = spapr_rtc_import_offset(&spapr->rtc, spapr->rtc_offset);
> > > >      }
> > > >  
> > > > +    if (spapr->patb_entry) {
> > > > +        if (kvmppc_has_cap_mmu_radix() && kvm_enabled()) {
> > > > +            err = kvmppc_configure_v3_mmu(POWERPC_CPU(first_cpu),
> > > > +                                          spapr->patb_flags &
> > > > +                                          SPAPR_PROC_TABLE_RADIX,
> > > > +                                          spapr->patb_flags &
> > > > +                                          SPAPR_PROC_TABLE_GTSE,
> > > 
> > > You should be able to work out the things you need here from
> > > patb_entry without adding the new patb_flags field.
> > 
> > kvmppc_configure_v3_mmu() needs two bools: radix and gtse. The radix
> > bit can be implied from patb_entry, I needed patb_flags to get the
> > gtse value. Not immediately obvious of how to get gtse bit from patb_entry,
> > but let me take a relook.
> 
> Oh, sorry, you can't get GTSE from the patb_entry, but you can get it
> from the LPCR.

So I need to get GTSE from LPCR at the target after the LPCR has been updated
from the incoming stream (via vmstate_ppc_cpu vmsd). However we are also
in the middle of processing the incoming stream here (via spapr_post_load).
Can we be sure that spapr_post_load() processing happens after all
SPRs (and hence LPCR) have been updated via vmstate_ppc_cpu vmsd handlers ?

Also, in addition to issuing KVM_PPC_CONFIGURE_V3_MMU, should we be
walking all the CPUs and setting the LPCR_UPRT and LPCR_GTSE bits like how
H_REGISTER_PROC_TBL does ?

Regards,
Bharata.