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

[Max Gurtovoy <mgurtovoy@nvidia.com>]

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).


>
> 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;
>