On 02/09/16 14:08, Thomas Gleixner wrote:
> On Thu, 1 Sep 2016, Marc Zyngier wrote:
>> On 01/09/16 09:15, majun (F) wrote:
>> Well, this issue goes way beyond the hack you wanted to add to the
>> generic code, and it should probably be addressed in the GIC code
>> itself, as an implementation specific workaround. Without knowing the
>> details of the erratum, it is difficult to think of that would be
>> required. I can come up with something like this:
>>
>> irqnr = gic_read_iar();
>> if (unlikely(!is_enabled(irqnr))) {
>> gic_write_eoir(irqnr);
>> if (static_key_true(&supports_deactivate))
>> gic_write_dir(irqnr);
>> set_pending(irqnr);
>> continue;
>> }
>>
>> Performance will suffer (an extra MMIO access on the fast path). If LPIs
>> are also affected, then the ITS code also needs to be involved, and
>> that's not going to be pretty either. This code will have to be enabled
>> at runtime, and handled like other erratum we have in this code.
>
> So that's certainly a required workaround at the gic level. Though I really
> think that we should make handle_percpu_devid_irq robust against a spurious
> interrupt.
>
>> void handle_percpu_devid_irq(unsigned int irq, struct irq_desc *desc)
>> {
>> - struct irq_chip *chip = irq_desc_get_chip(desc);
>> - struct irqaction *action = desc->action;
>> - void *dev_id = raw_cpu_ptr(action->percpu_dev_id);
>> + struct irq_chip *chip = NULL;
>> + struct irqaction *action;
>> + void *dev_id;
>> irqreturn_t res;
>>
>> + action = desc->action;
>> +
>> + /* Unexpected interrupt in some execption case
>> + * we just send eoi to end this interrupt
>> + */
>> + if (unlikely(!action)) {
>> + mask_irq(desc);
>
> This is wrong. mask_irq() does not work for percpu interrupts. Aside of that
> this completely lacks any debug information which tells us that there is
> something wrong in the system. I'm going to apply the patch below for
> robustness sake.
>
> Thanks,
>
> tglx
>
> 8<----------------------
> Subject: genirq: Robustify handle_percpu_devid_irq()
> From: Thomas Gleixner <t...@linutronix.de>
> Date: Fri, 02 Sep 2016 14:45:19 +0200
>
> The percpu_devid handler is not robust against spurious interrupts. If a
> spurious interrupt happens and no action is installed then the handler crashes
> with a NULL pointer dereference.
>
> Add a sanity check for this and log the wreckage once in dmesg.
>
> Reported-by: Majun <majun...@huawei.com>
> Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Looks fine to me.
Acked-by: Marc Zyngier <marc.zyng...@arm.com>
M.
--
Jazz is not dead. It just smells funny...
