Re: [Qemu-devel] [PATCH v4 1/5] spapr: Implement dispatch counter and prod bit on tcg

[David Gibson]

On Tue, Jul 16, 2019 at 07:27:22PM +1000, Nicholas Piggin wrote:
> David Gibson's on July 16, 2019 5:34 pm:
> > On Tue, Jul 16, 2019 at 12:47:22PM +1000, Nicholas Piggin wrote:
> >> Implement cpu_exec_enter/exit on ppc which calls into new methods of
> >> the same name in PPCVirtualHypervisorClass. These are used by spapr
> >> to implement these splpar elements, used in subsequent changes.
> >> 
> >> Signed-off-by: Nicholas Piggin <address@hidden>
> >> ---
> >>  hw/ppc/spapr.c                  | 25 +++++++++++++++++++++++++
> >>  hw/ppc/spapr_cpu_core.c         |  5 ++++-
> >>  hw/ppc/spapr_hcall.c            |  5 -----
> >>  include/hw/ppc/spapr.h          |  7 +++++++
> >>  include/hw/ppc/spapr_cpu_core.h |  2 ++
> >>  target/ppc/cpu.h                |  2 ++
> >>  target/ppc/translate_init.inc.c | 25 +++++++++++++++++++++++++
> >>  7 files changed, 65 insertions(+), 6 deletions(-)
> > 
> > Mostly LGTM.  Please do address the style issues that the bot
> > reported.
> 
> Will do.
> 
> > In addition, do the dispatch_counter and prod values need to be
> > migrated?
> 
> I was thinking no, it should be just a blip. But could the guest
> be reading the dispatch counter in the vpa for some other reason?
> There are other (unimplemented) dispatch statistics in there AFAIKS.
> Linux doesn't, but others might.

Right, I guess it's a question of whether a guest would get confused
if the dispatch count suddenly resets.

> And what about KVM, does any of the VPA data get migrated for 
> KVM guests?

Well, the stuff that's actually written into the VPA is implicitly
migrated, since it's part of guest memory.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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