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

[Nicholas Piggin]

David Gibson's on July 17, 2019 11:51 am:
> 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.

Linux wouldn't AFAIKS, but...

>> 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.

Yeah I just sent a patch which uses the VPA directly, so it matches
KVM and should get migrated.

Thanks,
Nick