Re: [Qemu-devel] [PATCH v2] vfio/pci: Support error recovery

[Cao jin]

On 01/10/2017 11:11 PM, Michael S. Tsirkin wrote:
> On Tue, Jan 10, 2017 at 07:46:17PM +0800, Cao jin wrote:
>>
>>
>> On 01/10/2017 07:04 AM, Michael S. Tsirkin wrote:
>>> On Sat, Dec 31, 2016 at 05:15:36PM +0800, Cao jin wrote:
>>>> Support serious device error recovery
>>>
>>> serious?
>>>
>>
>> Sorry for my poor vocabulary if it confuses people. I wanted to express
>> the meaning that: vfio-pci actually cannot do a real recovery for device
>> even if it provides the callbacks, it relies on the user to do a
>> effective(or word "serious"?) recovery.
>>
>> Welcome the amendment on the commit log.
> 
> It's up to Alex, maybe he's able to figure it all out from
> code, but the rest of us could benefit from a description
> of what the patch does from userspace point of view.
> 
> Also, is it a pre-requisite of the userspace patches you posted?
> 

Yes, it is.
-- 
Sincerely,
Cao jin

>>>>
>>>> Signed-off-by: Cao jin <address@hidden>
>>>> ---
>>>>  drivers/vfio/pci/vfio_pci.c         | 70 
>>>> +++++++++++++++++++++++++++++++++++--
>>>>  drivers/vfio/pci/vfio_pci_private.h |  2 ++
>>>>  2 files changed, 70 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
>>>> index 712a849..752af20 100644
>>>> --- a/drivers/vfio/pci/vfio_pci.c
>>>> +++ b/drivers/vfio/pci/vfio_pci.c
>>>> @@ -534,6 +534,15 @@ static long vfio_pci_ioctl(void *device_data,
>>>>  {
>>>>    struct vfio_pci_device *vdev = device_data;
>>>>    unsigned long minsz;
>>>> +  int ret;
>>>> +
>>>> +  if (vdev->aer_recovering && (cmd == VFIO_DEVICE_SET_IRQS ||
>>>> +      cmd == VFIO_DEVICE_RESET || cmd == VFIO_DEVICE_PCI_HOT_RESET)) {
>>>> +          ret = wait_for_completion_interruptible(
>>>> +                  &vdev->aer_completion);
>>>
>>> don't split it like that.
>>>
>>>> +          if (ret)
>>>> +                  return ret;
>>>> +  }
>>>>  
>>>>    if (cmd == VFIO_DEVICE_GET_INFO) {
>>>>            struct vfio_device_info info;
>>>> @@ -953,6 +962,15 @@ static ssize_t vfio_pci_rw(void *device_data, char 
>>>> __user *buf,
>>>>  {
>>>>    unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
>>>>    struct vfio_pci_device *vdev = device_data;
>>>> +  int ret;
>>>> +
>>>> +  /* block all kinds of access during host recovery */
>>>> +  if (vdev->aer_recovering) {
>>>> +          ret = wait_for_completion_interruptible(
>>>> +                  &vdev->aer_completion);
>>>> +          if (ret)
>>>> +                  return ret;
>>>> +  }
>>>>  
>>>>    if (index >= VFIO_PCI_NUM_REGIONS + vdev->num_regions)
>>>>            return -EINVAL;
>>>> @@ -1117,6 +1135,7 @@ static int vfio_pci_probe(struct pci_dev *pdev, 
>>>> const struct pci_device_id *id)
>>>>    vdev->irq_type = VFIO_PCI_NUM_IRQS;
>>>>    mutex_init(&vdev->igate);
>>>>    spin_lock_init(&vdev->irqlock);
>>>> +  init_completion(&vdev->aer_completion);
>>>>  
>>>>    ret = vfio_add_group_dev(&pdev->dev, &vfio_pci_ops, vdev);
>>>>    if (ret) {
>>>> @@ -1176,6 +1195,9 @@ static pci_ers_result_t 
>>>> vfio_pci_aer_err_detected(struct pci_dev *pdev,
>>>>  {
>>>>    struct vfio_pci_device *vdev;
>>>>    struct vfio_device *device;
>>>> +  u32 uncor_status;
>>>> +  unsigned int aer_cap_offset;
>>>> +  int ret;
>>>>  
>>>>    device = vfio_device_get_from_dev(&pdev->dev);
>>>>    if (device == NULL)
>>>> @@ -1187,10 +1209,29 @@ static pci_ers_result_t 
>>>> vfio_pci_aer_err_detected(struct pci_dev *pdev,
>>>>            return PCI_ERS_RESULT_DISCONNECT;
>>>>    }
>>>>  
>>>> +  /*
>>>> +   * get device's uncorrectable error status as soon as possible,
>>>
>>> should be "Get".
>>>
>>>> +   * and signal it to user space. The later we read it, the possibility
>>>> +   * the register value is mangled grows.
>>>> +   */
>>>> +  aer_cap_offset = pci_find_ext_capability(vdev->pdev, 
>>>> PCI_EXT_CAP_ID_ERR);
>>>> +  ret = pci_read_config_dword(vdev->pdev, aer_cap_offset +
>>>> +                                    PCI_ERR_UNCOR_STATUS, &uncor_status);
>>>> +        if (ret)
>>>> +                return PCI_ERS_RESULT_DISCONNECT;
>>>> +
>>>> +  pr_info("device %d got AER detect notification. uncorrectable error 
>>>> status = 0x%x\n", pdev->devfn, uncor_status);//to be removed
>>>
>>> Pls drop this.
>>>
>>>>    mutex_lock(&vdev->igate);
>>>>  
>>>> -  if (vdev->err_trigger)
>>>> -          eventfd_signal(vdev->err_trigger, 1);
>>>> +  vdev->aer_recovering = true;
>>>> +  reinit_completion(&vdev->aer_completion);
>>>> +
>>>> +  if (vdev->err_trigger && uncor_status) {
>>>> +          pr_info("device %d signal uncor status 0x%x to user",
>>>> +                  pdev->devfn, uncor_status);
>>>> +          /* signal uncorrectable error status to user space */
>>>> +          eventfd_signal(vdev->err_trigger, uncor_status);
>>>> +        }
>>>>  
>>>>    mutex_unlock(&vdev->igate);
>>>>  
>>>> @@ -1199,8 +1240,33 @@ static pci_ers_result_t 
>>>> vfio_pci_aer_err_detected(struct pci_dev *pdev,
>>>>    return PCI_ERS_RESULT_CAN_RECOVER;
>>>>  }
>>>>  
>>>> +static void vfio_pci_aer_resume(struct pci_dev *pdev)
>>>> +{
>>>> +  struct vfio_pci_device *vdev;
>>>> +  struct vfio_device *device;
>>>> +
>>>> +  device = vfio_device_get_from_dev(&pdev->dev);
>>>> +  if (device == NULL)
>>>> +          return;
>>>> +
>>>> +  vdev = vfio_device_data(device);
>>>> +  if (vdev == NULL) {
>>>> +          vfio_device_put(device);
>>>> +          return;
>>>> +  }
>>>> +
>>>> +  mutex_lock(&vdev->igate);
>>>> +  vdev->aer_recovering = false;
>>>> +  mutex_unlock(&vdev->igate);
>>>> +
>>>> +  complete_all(&vdev->aer_completion);
>>>> +
>>>> +  vfio_device_put(device);
>>>> +}
>>>> +
>>>>  static const struct pci_error_handlers vfio_err_handlers = {
>>>>    .error_detected = vfio_pci_aer_err_detected,
>>>> +  .resume         = vfio_pci_aer_resume,
>>>>  };
>>>>  
>>>>  static struct pci_driver vfio_pci_driver = {
>>>> diff --git a/drivers/vfio/pci/vfio_pci_private.h 
>>>> b/drivers/vfio/pci/vfio_pci_private.h
>>>> index 8a7d546..ba8471f 100644
>>>> --- a/drivers/vfio/pci/vfio_pci_private.h
>>>> +++ b/drivers/vfio/pci/vfio_pci_private.h
>>>> @@ -83,6 +83,8 @@ struct vfio_pci_device {
>>>>    bool                    bardirty;
>>>>    bool                    has_vga;
>>>>    bool                    needs_reset;
>>>> +  bool                    aer_recovering;
>>>> +  struct completion       aer_completion;
>>>>    struct pci_saved_state  *pci_saved_state;
>>>>    int                     refcnt;
>>>>    struct eventfd_ctx      *err_trigger;
>>>> -- 
>>>> 1.8.3.1
>>>>
>>>>
>>>
>>> How about some explanation about what is going on here?  All these
>>> changes seem racy since any number of errors can trigger at any time.
>>>
>>
>>
> 
> 
> .
> 

-- 
Sincerely,
Cao jin