Looks good.
Reviewed-by: Marcelo Tosatti <mtosa...@redhat.com>
On Thu, Aug 29, 2019 at 06:18:42PM -0300, Eduardo Habkost wrote:
> CCing Marcelo, who wrote kvm_update_clock() and
> kvmclock_pre_save().
>
> On Thu, Aug 29, 2019 at 06:07:11PM -0300, Maxiwell S. Garcia wrote:
> > The clock move makes the guest knows about the paused time between the
> > 'stop' and 'migrate' commands. This is an issue in an already-paused
> > VM because some side effects, like process stalls, could happen
> > after migration.
> >
> > So, this patch checks the runstate of guest in the pre_save handler and
> > do not re-reads the clock in case of paused state (cold migration).
> >
> > Signed-off-by: Maxiwell S. Garcia <maxiw...@linux.ibm.com>
> > ---
> > hw/i386/kvm/clock.c | 15 +++++++++++----
> > 1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
> > index 80c133a724..2c59b6894b 100644
> > --- a/hw/i386/kvm/clock.c
> > +++ b/hw/i386/kvm/clock.c
> > @@ -41,6 +41,9 @@ typedef struct KVMClockState {
> > uint64_t clock;
> > bool clock_valid;
> >
> > + /* whether the 'clock' value was obtained in the 'paused' state */
> > + bool runstate_paused;
> > +
> > /* whether machine type supports reliable KVM_GET_CLOCK */
> > bool mach_use_reliable_get_clock;
> >
> > @@ -202,6 +205,8 @@ static void kvmclock_vm_state_change(void *opaque, int
> > running,
> > return;
> > }
> >
> > + s->runstate_paused = runstate_check(RUN_STATE_PAUSED);
> > +
> > kvm_synchronize_all_tsc();
> >
> > kvm_update_clock(s);
> > @@ -260,9 +265,9 @@ static int kvmclock_pre_load(void *opaque)
> > }
> >
> > /*
> > - * When migrating, read the clock just before migration,
> > - * so that the guest clock counts during the events
> > - * between:
> > + * When migrating a running guest, read the clock just
> > + * before migration, so that the guest clock counts
> > + * during the events between:
> > *
> > * * vm_stop()
> > * *
> > @@ -277,7 +282,9 @@ static int kvmclock_pre_save(void *opaque)
> > {
> > KVMClockState *s = opaque;
> >
> > - kvm_update_clock(s);
> > + if (!s->runstate_paused) {
> > + kvm_update_clock(s);
> > + }
> >
> > return 0;
> > }
> > --
> > 2.20.1
> >
>
> --
> Eduardo
