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

[Max Gurtovoy <mgurtovoy@nvidia.com>]

On 4/8/2021 3:45 PM, Jason Wang wrote:
>
> 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?

If the device didn't write 0 to status I guess we don't need that.

The device shouldn't raise any interrupt before negotiation finish 
successfully.

MST, is that correct ?

>
> 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;
>>>
>>
>