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

[Richard Henderson]

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~
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