Re: [Qemu-devel] [RFC QEMU 1/2] arm/virt: Initialize generic timer scale factor dynamically

[Bijan Mottahedeh]

On 11/8/2018 6:21 AM, Richard Henderson wrote:
> On 11/7/18 7:48 PM, Bijan Mottahedeh wrote:
> >   
> > +static void set_system_clock_scale(void)
> > +{
> > +    unsigned long cntfrq_el0;
> > +
> > +    asm volatile("mrs %0, cntfrq_el0" : "=r"(cntfrq_el0));
> > +
> > +    if (cntfrq_el0 == 0) {
> > +        cntfrq_el0 = GTIMER_SCALE_DEF;
> > +    }
> > +
> > +    system_clock_scale = NANOSECONDS_PER_SECOND / (int)cntfrq_el0;
> > +}
> This only works for kvm.
>
> For TCG you need to use the default always.  In particular, it won't even
> compile for an x86 host.
>
>
> r~
Is it ok to ifdef the asm statement with CONFIG_KVM, or what would be 
the correct way to account for TCG vs. KVM?

Thanks.

--bijan