Re: [PATCH v8 20/28] KVM: arm64: Add clock support for the pKVM hyp

[Vincent Donnefort <vdonnefort@google.com>]

[...]

> > +/* Using host provided data. Do not use for anything else than debugging. */
> > +u64 trace_clock(void)
> > +{
> > +	struct clock_data *clock = &trace_clock_data;
> > +	u64 bank = smp_load_acquire(&clock->cur);
> > +	u64 cyc, ns;
> > +
> > +	cyc = __arch_counter_get_cntpct() - clock->data[bank].epoch_cyc;
> 
> I can only imagine that you don't care about the broken systems that
> do not have a monotonic counter, and that will happily have their
> counter swing back and forth?

I haven't used the _stable() variant for the affected devices... Hum this will
not be trivial from the hypervisor. I'll see what I can do.

> 
> Also, you may want to document why you are using the physical counter
> instead of the virtual one. I guess that you don't want CNTVOFF_EL2 to
> apply when HCR_EL2.E2H==0, but given that you never allow anything
> else for pKVM, this is slightly odd.

You mean I might as well use __arch_counter_get_cntvct() as CNTVOFF_EL2 will
always be ignored in the pKVM case?

> 
> Thanks,
> 
> 	M.
> 
> -- 
> Without deviation from the norm, progress is not possible.