Re: [Qemu-devel] [PATCH V3] Guest stop notification

[Eric B Munson]

On Fri, 02 Dec 2011, Jan Kiszka wrote:

> On 2011-12-02 20:19, Eric B Munson wrote:
> > Often when a guest is stopped from the qemu console, it will report spurious
> > soft lockup warnings on resume.  There are kernel patches being discussed 
> > that
> > will give the host the ability to tell the guest that it is being stopped 
> > and
> > should ignore the soft lockup warning that generates.
> > 
> > Signed-off-by: Eric B Munson <address@hidden>
> > Cc: Avi Kivity <address@hidden>
> > Cc: Marcelo Tosatti <address@hidden>
> > Cc: Jan Kiszka <address@hidden>
> > Cc: address@hidden
> > Cc: address@hidden
> > Cc: address@hidden
> > 
> > ---
> > Changes from V2:
> >  Move ioctl into hw/kvmclock.c so as other arches can use it as it is
> > implemented
> > 
> > Changes from V1:
> >  Remove unnecessary encapsulating function
> > 
> >  hw/kvmclock.c |   24 ++++++++++++++++++++++++
> >  1 files changed, 24 insertions(+), 0 deletions(-)
> > 
> > diff --git a/hw/kvmclock.c b/hw/kvmclock.c
> > index 5388bc4..756839f 100644
> > --- a/hw/kvmclock.c
> > +++ b/hw/kvmclock.c
> > @@ -16,6 +16,7 @@
> >  #include "sysbus.h"
> >  #include "kvm.h"
> >  #include "kvmclock.h"
> > +#include "cpu-all.h"
> >  
> >  #include <linux/kvm.h>
> >  #include <linux/kvm_para.h>
> > @@ -69,11 +70,34 @@ static void kvmclock_vm_state_change(void *opaque, int 
> > running,
> >      }
> >  }
> >  
> > +static void kvmclock_vm_state_change_vcpu(void *opaque, int running,
> > +                                          RunState state)
> > +{
> > +    int ret;
> > +    CPUState *penv = first_cpu;
> > +
> > +    if (running) {
> > +   while (penv) {
> 
> or: for (cpu = first_cpu; cpu != NULL; cpu = cpu->next_cpu) {
> 

Functionally equivalent and I see both in the code, is there a standard?

> > +            ret = kvm_vcpu_ioctl(penv, KVM_GUEST_PAUSED, 0);
> > +            if (ret) {
> > +                if (ret != ENOSYS) {
> > +                    fprintf(stderr,
> > +                            "kvmclock_vm_state_change_vcpu: %s\n",
> > +                            strerror(-ret));
> > +                }
> > +                return;
> > +            }
> > +            penv = (CPUState *)penv->next_cpu;
> 
> Unneeded cast.
> 

Also following an example seen elsewhere.

> > +        }
> > +    }
> > +}
> > +
> 
> Again: please use checkpatch.pl.
> 

Sorry, tough to get used to hitting space bar that many times...

> >  static int kvmclock_init(SysBusDevice *dev)
> >  {
> >      KVMClockState *s = FROM_SYSBUS(KVMClockState, dev);
> >  
> >      qemu_add_vm_change_state_handler(kvmclock_vm_state_change, s);
> > +    qemu_add_vm_change_state_handler(kvmclock_vm_state_change_vcpu, NULL);
> >      return 0;
> >  }
> >  
> 
> Why not extend the existing handler?

Because the new handler doesn't touch the KVMClockState object.  If this is
preferred, I have no objection.

> 
> I still wonder if the IOCTL interface is actually kvmclock specific. But
> Marcello asked for this, and we could still change it when some arch
> comes around that provides it independent of kvmclock.

The flag itself is stored in the pvclock_vcpu_time_info structure, and anything
else that touches that structure uses ioctls.

> 
> Jan
>

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