Re: [PATCH 5/5] KVM: paravirt time source

Jeremy Fitzhardinge wrote:

Anthony Liguori wrote:
  

quoted

+static cycle_t read_hyper(void)
+{
+	struct timespec now;
+	int ret;
+
+	ret = kvm_hypercall(KVM_HYPERCALL_GET_KTIME, (u32)&now, 0, 0, 0);
+	WARN_ON(ret);
+
+	return now.tv_nsec + now.tv_sec * (cycles_t)1e9;
  
    

Hm, use of FP looks pretty odd.  I guess its OK to assume the compiler
will completely remove all the FP stuff at compile time.  Or you could
use NSEC_PER_SEC.
  

Agreed.

quoted

+}
+
+static struct clocksource clocksource_hyper = {
+	.name			= "hyper",
+	.rating			= 200,
  
    

We should probably standardize on this.  I guess that if you're in a
paravirt environment, and there's a paravirt clocksource, that would
always be the best clocksource to use.

  

quoted

+	.read			= read_hyper,
+	.mask			= CLOCKSOURCE_MASK(64),
+	.mult			= 1,
+	.shift			= 0,
  
    

It would be better to use a scale and shift here, so that adjtime has
something to work with when warping time.
  

Okay.  I may remove this patch from the patch series and attempt to sit 
down next week and work out something more complete that also implements 
stolen time accounting.

Regards,

Anthony Liguori

    J

  

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