Re: [PATCH v2 2/3] virito_pci: add timeout to reset device operation

Jason Wang
2021-04-08T12:45:57Z

在 2021/4/8 下午5:44, Max Gurtovoy 写道:
>
> On 4/8/2021 12:01 PM, Jason Wang wrote:
>>
>> 在 2021/4/8 下午4:11, Max Gurtovoy 写道:
>>> According to the spec after writing 0 to device_status, the driver MUST
>>> wait for a read of device_status to return 0 before reinitializing the
>>> device. In case we have a device that won't return 0, the reset
>>> operation will loop forever and cause the host/vm to stuck. Set timeout
>>> for 3 minutes before giving up on the device.
>>>
>>> Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
>>> ---
>>>   drivers/virtio/virtio_pci_modern.c | 10 +++++++++-
>>>   1 file changed, 9 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/virtio/virtio_pci_modern.c
>>> b/drivers/virtio/virtio_pci_modern.c
>>> index cc3412a96a17..dcee616e8d21 100644
>>> --- a/drivers/virtio/virtio_pci_modern.c
>>> +++ b/drivers/virtio/virtio_pci_modern.c
>>> @@ -162,6 +162,7 @@ static int vp_reset(struct virtio_device *vdev)
>>>   {
>>>       struct virtio_pci_device *vp_dev = to_vp_device(vdev);
>>>       struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
>>> +    unsigned long timeout = jiffies + msecs_to_jiffies(180000);
>>>         /* 0 status means a reset. */
>>>       vp_modern_set_status(mdev, 0);
>>> @@ -169,9 +170,16 @@ static int vp_reset(struct virtio_device *vdev)
>>>        * device_status to return 0 before reinitializing the device.
>>>        * This will flush out the status write, and flush in device
>>> writes,
>>>        * including MSI-X interrupts, if any.
>>> +     * Set a timeout before giving up on the device.
>>>        */
>>> -    while (vp_modern_get_status(mdev))
>>> +    while (vp_modern_get_status(mdev)) {
>>> +        if (time_after(jiffies, timeout)) {
>>
>>
>> What happens if the device finish the rest after the timeout?
>
>
> The driver will set VIRTIO_CONFIG_S_FAILED and one can re-probe it
> later on (e.g by re-scanning the pci bus).

Ok, so do we need the flush through vp_synchronize_vectors() here?

Thanks

>
>
>>
>> Thanks
>>
>>
>>> +            dev_err(&vdev->dev, "virtio: device not ready. "
>>> +                "Aborting. Try again later\n");
>>> +            return -EAGAIN;
>>> +        }
>>>           msleep(1);
>>> +    }
>>>       /* Flush pending VQ/configuration callbacks. */
>>>       vp_synchronize_vectors(vdev);
>>>       return 0;
>>
>