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

Fu Wei
2017-01-17T23:49:45Z

Hi Mark,

On 17 January 2017 at 01:29, Mark Rutland <mark.rutland@arm.com> wrote:
> 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).

Great thanks for pointing it out, that is bug.
also got this bug report from Huawei engineer.

I have fixed it using your example code, thanks!

>
>> +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.

Yes, that is the reason of the duplication :-)

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

Done, thanks :-)

>
> Thanks,
> Mark.

--
Best regards,

Fu Wei
Software Engineer
Red Hat