Re: [PATCH v19 05/15] clocksource/drivers/arm_arch_timer: rework PPI determination

Mark Rutland
2017-01-16T17:29:28Z

On Wed, Dec 21, 2016 at 02:45:53PM +0800, fu.wei@linaro.org wrote:
[...]

> - if (is_hyp_mode_available() || !arch_timer_ppi[ARCH_TIMER_VIRT_PPI]) {
> - bool has_ppi;
> + if (is_hyp_mode_available() && is_kernel_in_hyp_mode())
> + return ARCH_TIMER_HYP_PPI;
>
> - if (is_kernel_in_hyp_mode()) {
> - arch_timer_uses_ppi = ARCH_TIMER_HYP_PPI;
> - has_ppi = !!arch_timer_ppi[ARCH_TIMER_HYP_PPI];
> - } else {
> - arch_timer_uses_ppi = ARCH_TIMER_PHYS_SECURE_PPI;
> - has_ppi = (!!arch_timer_ppi[ARCH_TIMER_PHYS_SECURE_PPI] ||
> - !!arch_timer_ppi[ARCH_TIMER_PHYS_NONSECURE_PPI]);
> - }
> + if (arch_timer_ppi[ARCH_TIMER_VIRT_PPI])
> + return ARCH_TIMER_VIRT_PPI;
>
> - if (!has_ppi) {
> - pr_warn("No interrupt available, giving up\n");
> - return -EINVAL;
> - }
> - }
> + if (IS_ENABLED(CONFIG_ARM64))
> + return ARCH_TIMER_PHYS_NONSECURE_PPI;
> +
> + return ARCH_TIMER_PHYS_SECURE_PPI;

For a 32-bit platform booted at hyp (with a virt PPI available), the new
logic will select ARCH_TIMER_VIRT_PPI. I beleive that will break KVM.

I think the logic should be:

if (is_kernel_in_hyp_mode())
return ARCH_TIMER_HYP_PPI;

if (!is_hyp_mode_available() &&
arch_timer_ppi[ARCH_TIMER_VIRT_PPI])
return ARCH_TIMER_VIRT_PPI;

if (IS_ENABLED(CONFIG_ARM64))
return ARCH_TIMER_PHYS_NONSECURE_PPI;

return ARCH_TIMER_PHYS_SECURE_PPI;

Please use that instead (keeping the comment you retained).

> +static int __init arch_timer_init(void)
> +{
> + int ret;
>
> ret = arch_timer_register();
> if (ret)
> @@ -904,6 +906,13 @@ static int __init arch_timer_of_init(struct device_node *np)
> if (IS_ENABLED(CONFIG_ARM) &&
> of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
> arch_timer_uses_ppi = ARCH_TIMER_PHYS_SECURE_PPI;
> + else
> + arch_timer_uses_ppi = arch_timer_select_ppi();
> +
> + if (!arch_timer_ppi[arch_timer_uses_ppi]) {
> + pr_err("No interrupt available, giving up\n");
> + return -EINVAL;
> + }
>
> /* On some systems, the counter stops ticking when in suspend. */
> arch_counter_suspend_stop = of_property_read_bool(np,
> @@ -1049,6 +1058,12 @@ static int __init arch_timer_acpi_init(struct acpi_table_header *table)
> /* Get the frequency from CNTFRQ */
> arch_timer_detect_rate(NULL, NULL);
>
> + arch_timer_uses_ppi = arch_timer_select_ppi();
> + if (!arch_timer_ppi[arch_timer_uses_ppi]) {
> + pr_err("No interrupt available, giving up\n");
> + return -EINVAL;
> + }

I see that we have to duplicate this so we can special-case the
DT-specific behaviour, so that's fine by me.

If you can fix the arch_timer_select_ppi() logic as above, this should
be fine.

Thanks,
Mark.