Re: [PATCH 12/17] Add helper function get_kernel_ns

[Zachary Amsden]

On 06/14/2010 10:41 PM, Avi Kivity wrote:
> On 06/15/2010 10:34 AM, Zachary Amsden wrote:
> > Add a helper function for the multiple places this is used.  Note 
> > that it
> > must not be called in preemptible context, as that would mean the kernel
> > could enter software suspend state, which would cause non-atomic 
> > operation
> > of the monotonic_to_bootbased computation.
> >
> > Open question: should the KVM_SET_CLOCK / KVM_GET_CLOCK ioctls use this
> > as well?  Currently, they are not bootbased (but perhaps should be).
> >
> > Signed-off-by: Zachary Amsden<zamsden@xxxxxxxxxx>
> > ---
> >   arch/x86/kvm/x86.c |   26 +++++++++++++-------------
> >   1 files changed, 13 insertions(+), 13 deletions(-)
> >
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 703ea43..15c7317 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -915,6 +915,16 @@ static void kvm_get_time_scale(uint32_t 
> > scaled_khz, uint32_t base_khz,
> >            __func__, base_khz, scaled_khz, shift, *pmultiplier);
> >   }
> >
> > +static inline u64 get_kernel_ns(void)
> > +{
> > +    struct timespec ts;
> > +
> > +    WARN_ON(preemptible());
> > +    ktime_get_ts(&ts);
> > +    monotonic_to_bootbased(&ts);
> > +    return timespec_to_ns(&ts);
> > +}
> > +
> >   static DEFINE_PER_CPU(unsigned long, cpu_tsc_khz);
>
> Isn't something like this a candidate for the time infrastructure?

Should it be?  It certainly seems reasonable.


Also, should we be using it for the cases KVM_GET_CLOCK / 
KVM_SET_CLOCK?  It seems global kvmclock_offset for the VM ignores the 
bootbased conversion.

Zach
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