On 13.12.17 20:29, Laurent Vivier wrote: > On 13/12/2017 20:19, Alexander Graf wrote: >> >> >> On 02.02.17 06:14, David Gibson wrote: >>> From: Laurent Vivier <lviv...@redhat.com> >>> >>> This is a port to ppc of the i386 commit: >>> 00f4d64 kvmclock: clock should count only if vm is running >>> >>> We remove timebase_post_load function, and use the VM state >>> change handler to save and restore the guest_timebase (on stop >>> and continue). >>> >>> We keep timebase_pre_save to reduce the clock difference on >>> migration like in: >>> 6053a86 kvmclock: reduce kvmclock difference on migration >>> >>> Time base offset has originally been introduced by commit >>> 98a8b52 spapr: Add support for time base offset migration >>> >>> So while VM is paused, the time is stopped. This allows to have >>> the same result with date (based on Time Base Register) and >>> hwclock (based on "get-time-of-day" RTAS call). >>> >>> Moreover in TCG mode, the Time Base is always paused, so this >>> patch also adjust the behavior between TCG and KVM. >>> >>> VM state field "time_of_the_day_ns" is now useless but we keep >>> it to be able to migrate to older version of the machine. >>> >>> As vmstate_ppc_timebase structure (with timebase_pre_save() and >>> timebase_post_load() functions) was only used by vmstate_spapr, >>> we register the VM state change handler only in ppc_spapr_init(). >>> >>> Signed-off-by: Laurent Vivier <lviv...@redhat.com> >>> Signed-off-by: David Gibson <da...@gibson.dropbear.id.au> >> >> Just a small heads-up: I've been debugging an OpenQA regression lately >> where our automated testing regressed with QEMU 2.9. With stock 2.9.1, I >> get a failure rate of "weird" effects (probably TB divergence between >> vcpus) of ~30%. With this patch reverted it's back to 0%. >> >> I *think* something here causes the TB offset of multiple threads (I'm >> running -smp 2,threads=2) to diverge. >> >> I'll keep debugging things tomorrow, but I'll be happy to see anyone >> else beat me to analyze what is going wrong ;). > > Don't know if it can be related, but for migration we need:
I doubt that fixes it, but I'll give it a try and will let you know the results :). Alex
