On 2019/1/31 23:12, Marc Zyngier wrote:
> Hi Zeng,
>
> On 31/01/2019 14:47, Zheng Xiang wrote:
>> Hi Marc,
>>
>> On 2019/1/29 13:42, Zheng Xiang wrote:
>>> On 2019/1/28 21:51, Marc Zyngier wrote:
>>>> On 28/01/2019 07:13, Zheng Xiang wrote:
>>>>> Hi Marc,
>>>>>
>>>>> Thanks for your review.
>>>>>
>>>>> On 2019/1/26 19:38, Marc Zyngier wrote:
>>>>>> Hi Zheng,
>>>>>>
>>>>>> On Sat, 26 Jan 2019 06:16:24 +0000,
>>>>>> Zheng Xiang <zhengxia...@huawei.com> wrote:
>>>>>>>
>>>>>>> Currently each PCI device under a PCI Bridge shares the same device id
>>>>>>> and ITS device. Assume there are two PCI devices call its_msi_prepare
>>>>>>> concurrently and they are both going to find and create their ITS
>>>>>>> device. There is a chance that the later one couldn't find ITS device
>>>>>>> before the other one creating the ITS device. It will cause the later
>>>>>>> one to create a different ITS device even if they have the same
>>>>>>> device_id.
>>>>>>
>>>>>> Interesting finding. Is this something you've actually seen in practice
>>>>>> with two devices being probed in parallel? Or something that you found
>>>>>> by inspection?
>>>>>
>>>>> Yes, I find this problem after analyzing the reason of VM hung. At last, I
>>>>> find that the virtio-gpu cannot receive the MSI interrupts due to sharing
>>>>> a same event_id as virtio-serial.
>>>>>
>>>>> See https://lkml.org/lkml/2019/1/10/299 for the bug report.
>>>>>
>>>>> This problem can be reproducted with high probability by booting a
>>>>> Qemu/KVM
>>>>> VM with a virtio-serial controller and a virtio-gpu adding to a PCI Bridge
>>>>> and also adding some delay before creating ITS device.
>>>>
>>>> Fair enough. Do you mind sharing your QEMU command line? It'd be useful
>>>> if I could reproduce it here (and would give me a way to check that it
>>>> doesn't regress).
>>>
>>
>> Have you reproduced it with my QEMU command line?
>>
>> If so, should I send a V2 patch with your suggestion?
>
> I've queued the following, much more complete patch:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=irq/irqchip-next&id=9791ec7df0e7b4d80706ccea8f24b6542f6059e9
>
> Can you check that it works for you? I didn't manage to get the right
> timing conditions, but I also had issues getting virtio-gpu running on
> my TX2, so one might explain the other.
>
It works for my case, but I worried about the below lines which may
cause memory leak.
@@ -2627,8 +2640,14 @@ static void its_irq_domain_free(struct irq_domain
*domain, unsigned int virq,
irq_domain_reset_irq_data(data);
}
- /* If all interrupts have been freed, start mopping the floor */
- if (bitmap_empty(its_dev->event_map.lpi_map,
+ mutex_lock(&its->dev_alloc_lock);
+
+ /*
+ * If all interrupts have been freed, start mopping the
+ * floor. This is conditionned on the device not being shared.
+ */
+ if (!its_dev->shared &&
+ bitmap_empty(its_dev->event_map.lpi_map,
its_dev->event_map.nr_lpis)) {
its_lpi_free(its_dev->event_map.lpi_map,
its_dev->event_map.lpi_base,
It seems that the shared its_dev would never be freed since the value of
its_dev->shared is always *true*.
> Thanks,
>
> M.
>
--
Thanks,
Xiang
