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

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