Hi Mark,

On 17 January 2017 at 01:29, Mark Rutland [off-list ref] wrote:

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

quoted

-     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!

quoted

+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