Re: [PATCH v7 7/9] iommu/vt-d: Allow qi_submit_sync() to return the QI faults

[Ethan Zhao <haifeng.zhao@linux.intel.com>]

On 12/27/2023 5:06 PM, Duan, Zhenzhong wrote:
>
>> -----Original Message-----
>> From: Liu, Yi L <yi.l.liu@intel.com>
>> Sent: Tuesday, December 26, 2023 4:44 PM
>> Subject: Re: [PATCH v7 7/9] iommu/vt-d: Allow qi_submit_sync() to return
>> the QI faults
>>
>> On 2023/12/26 14:15, Yi Liu wrote:
>>>
>>> On 2023/12/26 12:13, Tian, Kevin wrote:
>>>>> From: Liu, Yi L <yi.l.liu@intel.com>
>>>>> Sent: Tuesday, December 26, 2023 12:03 PM
>>>>>
>>>>> On 2023/12/22 12:23, Tian, Kevin wrote:
>>>>>>> From: Liu, Yi L <yi.l.liu@intel.com>
>>>>>>> Sent: Thursday, December 21, 2023 11:40 PM
>>>>>>>
>>>>>>> +    fault &= DMA_FSTS_IQE | DMA_FSTS_ITE | DMA_FSTS_ICE;
>>>>>>> +    if (fault) {
>>>>>>> +        if (fsts)
>>>>>>> +            *fsts |= fault;
>>>>>> do we expect the fault to be accumulated? otherwise it's clearer to
>>>>>> just do direct assignment instead of asking for the caller to clear
>>>>>> the variable before invocation.
>>>>> not quite get. do you mean the fault should not be cleared in the caller
>>>>> side?
>>>>>
>>>> I meant:
>>>>
>>>>      if (fsts)
>>>>          *fsts = fault;
>>>>
>>>> unless there is a reason to *OR* the original value.
>>> I guess no such a reason. :) let me modify it.
>> hmmm, replied too soon. The qi_check_fault() would be called multiple
>> times in one invalidation circle as qi_submit_sync() needs to see if any
>> fault happened before the hw writes back QI_DONE to the wait descriptor.
>> There can be ICE which may eventually result in ITE. So caller of
>> qi_check_fault()
>> would continue to wait for QI_DONE. So qi_check_fault() returns 0 to let
>> qi_submit_sync() go on though ICE detected. If we use '*fsts = fault;',
>> then ICE would be missed since the input fsts pointer is the same in
>> one qi_submit_sync() call.
> Is it necessary to return fault to user if qi_check_fault() return -EAGAIN and
> a restart run succeeds?

Issue a device-TLB invalidation to no response device there is possibility

will be trapped there loop for ITE , never get return.

Thanks,

Ethan

> Thanks
> Zhenzhong