linux-kernel - Re: [PATCH v7 5/6] hisi_acc_vfio_pci: bugfix live migration function without VF device driver

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Message-ID: <460f52a8-7a4a-96f7-b0db-299d3cfc244c@huawei.com>
Date: Sat, 10 May 2025 15:41:12 +0800
From: liulongfang <liulongfang@...wei.com>
To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>,
	"alex.williamson@...hat.com" <alex.williamson@...hat.com>, "jgg@...dia.com"
	<jgg@...dia.com>, Jonathan Cameron <jonathan.cameron@...wei.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linuxarm@...neuler.org" <linuxarm@...neuler.org>
Subject: Re: [PATCH v7 5/6] hisi_acc_vfio_pci: bugfix live migration function
 without VF device driver

On 2025/4/15 16:45, Shameerali Kolothum Thodi wrote:
> 
> 
>> -----Original Message-----
>> From: liulongfang <liulongfang@...wei.com>
>> Sent: Friday, April 11, 2025 4:59 AM
>> To: alex.williamson@...hat.com; jgg@...dia.com; Shameerali Kolothum
>> Thodi <shameerali.kolothum.thodi@...wei.com>; Jonathan Cameron
>> <jonathan.cameron@...wei.com>
>> Cc: kvm@...r.kernel.org; linux-kernel@...r.kernel.org;
>> linuxarm@...neuler.org; liulongfang <liulongfang@...wei.com>
>> Subject: [PATCH v7 5/6] hisi_acc_vfio_pci: bugfix live migration function
>> without VF device driver
>>
>> If the VF device driver is not loaded in the Guest OS and we attempt to
>> perform device data migration, the address of the migrated data will
>> be NULL.
>> The live migration recovery operation on the destination side will
>> access a null address value, which will cause access errors.
>>
>> Therefore, live migration of VMs without added VF device drivers
>> does not require device data migration.
>> In addition, when the queue address data obtained by the destination
>> is empty, device queue recovery processing will not be performed.
>>
>> Fixes: b0eed085903e ("hisi_acc_vfio_pci: Add support for VFIO live
>> migration")
>> Signed-off-by: Longfang Liu <liulongfang@...wei.com>
>> Reviewed-by: Shameer Kolothum
>> <shameerali.kolothum.thodi@...wei.com>
>> ---
>>  .../vfio/pci/hisilicon/hisi_acc_vfio_pci.c    | 22 +++++++++++++------
>>  1 file changed, 15 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>> b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>> index cadc82419dca..d12a350440d3 100644
>> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>> @@ -426,13 +426,6 @@ static int vf_qm_check_match(struct
>> hisi_acc_vf_core_device *hisi_acc_vdev,
>>  		return -EINVAL;
>>  	}
>>
>> -	ret = qm_write_regs(vf_qm, QM_VF_STATE, &vf_data->vf_qm_state,
>> 1);
>> -	if (ret) {
>> -		dev_err(dev, "failed to write QM_VF_STATE\n");
>> -		return ret;
>> -	}
>> -
>> -	hisi_acc_vdev->vf_qm_state = vf_data->vf_qm_state;
>>  	hisi_acc_vdev->match_done = true;
>>  	return 0;
>>  }
>> @@ -498,6 +491,20 @@ static int vf_qm_load_data(struct
>> hisi_acc_vf_core_device *hisi_acc_vdev,
>>  	if (migf->total_length < sizeof(struct acc_vf_data))
>>  		return -EINVAL;
>>
>> +	if (!vf_data->eqe_dma || !vf_data->aeqe_dma ||
>> +	    !vf_data->sqc_dma || !vf_data->cqc_dma) {
>> +		dev_info(dev, "resume dma addr is NULL!\n");
>> +		hisi_acc_vdev->vf_qm_state = QM_NOT_READY;
>> +		return 0;
>> +	}
> 
> 
> I am still not fully understood why we need the above check. The only case as
> far as I can think of where this will happen is when the source VM Guest has
> not loaded the ACC driver. And we do take care of that already using vf_qm_state and
> checking total_length == QM_MATCH_SIZE.
> 
> Have you seen this happening in any other scenario during your tests?
>

This is a problem that was discovered and fixed in previous abnormal scenario tests.
In the abnormal tests, abnormal error handling was performed and real-time migration
was executed. However, due to the lack of this check, the device became abnormal
after migration.

Thanks,
Longfang.

> Thanks,
> Shameer
> 
>> +
>> +	ret = qm_write_regs(qm, QM_VF_STATE, &vf_data->vf_qm_state, 1);
>> +	if (ret) {
>> +		dev_err(dev, "failed to write QM_VF_STATE\n");
>> +		return -EINVAL;
>> +	}
>> +	hisi_acc_vdev->vf_qm_state = vf_data->vf_qm_state;
>> +
>>  	qm->eqe_dma = vf_data->eqe_dma;
>>  	qm->aeqe_dma = vf_data->aeqe_dma;
>>  	qm->sqc_dma = vf_data->sqc_dma;
>> @@ -1531,6 +1538,7 @@ static int hisi_acc_vfio_pci_migrn_init_dev(struct
>> vfio_device *core_vdev)
>>  	hisi_acc_vdev->vf_id = pci_iov_vf_id(pdev) + 1;
>>  	hisi_acc_vdev->pf_qm = pf_qm;
>>  	hisi_acc_vdev->vf_dev = pdev;
>> +	hisi_acc_vdev->vf_qm_state = QM_NOT_READY;
>>  	mutex_init(&hisi_acc_vdev->state_mutex);
>>  	mutex_init(&hisi_acc_vdev->open_mutex);
>>
>> --
>> 2.24.0
> 
> .
>