linux-kernel - Re: [PATCH v7 7/9] iommu/vt-d: Allow qi_submit

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Date: Wed, 27 Dec 2023 17:33:11 +0800
From: Ethan Zhao <haifeng.zhao@...ux.intel.com>
To: "Duan, Zhenzhong" <zhenzhong.duan@...el.com>,
 "Liu, Yi L" <yi.l.liu@...el.com>, "Tian, Kevin" <kevin.tian@...el.com>,
 "joro@...tes.org" <joro@...tes.org>,
 "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
 "jgg@...dia.com" <jgg@...dia.com>,
 "robin.murphy@....com" <robin.murphy@....com>,
 "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>
Cc: "cohuck@...hat.com" <cohuck@...hat.com>,
 "eric.auger@...hat.com" <eric.auger@...hat.com>,
 "nicolinc@...dia.com" <nicolinc@...dia.com>,
 "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
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 <shameerali.kolothum.thodi@...wei.com>, "lulu@...hat.com" <lulu@...hat.com>,
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 "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
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 "joao.m.martins@...cle.com" <joao.m.martins@...cle.com>,
 "Zeng, Xin" <xin.zeng@...el.com>, "Zhao, Yan Y" <yan.y.zhao@...el.com>,
 "j.granados@...sung.com" <j.granados@...sung.com>
Subject: Re: [PATCH v7 7/9] iommu/vt-d: Allow qi_submit_sync() to return the
 QI faults


On 12/27/2023 5:06 PM, Duan, Zhenzhong wrote:
>
>> -----Original Message-----
>> From: Liu, Yi L <yi.l.liu@...el.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@...el.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@...el.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