Re: [PATCH v6 5/5] hisi_acc_vfio_pci: bugfix live migration function without VF device driver

[Alex Williamson <alex.williamson@redhat.com>]

On Tue, 18 Mar 2025 14:45:48 +0800
Longfang Liu <liulongfang@huawei.com> wrote:

> 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@huawei.com>
> Reviewed-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> ---
>  .../vfio/pci/hisilicon/hisi_acc_vfio_pci.c    | 21 ++++++++++++-------
>  1 file changed, 14 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..68b1c7204cad 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 +491,13 @@ 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;
>  
> +	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;
> @@ -506,6 +506,12 @@ static int vf_qm_load_data(struct hisi_acc_vf_core_device *hisi_acc_vdev,
>  	qm->qp_base = vf_data->qp_base;
>  	qm->qp_num = vf_data->qp_num;
>  
> +	if (!vf_data->eqe_dma || !vf_data->aeqe_dma ||
> +	    !vf_data->sqc_dma || !vf_data->cqc_dma) {
> +		dev_err(dev, "resume dma addr is NULL!\n");
> +		return -EINVAL;
> +	}
> +

I'm not sure how this fits in based on the commit log.  IIUC, we're
actually rejecting the migration data here, which will cause a
migration failure.  We're also testing the validity of the data *after*
we've actually applied it to the hisi_qm object, which seems backwards.

Are we just not processing the migration data because there's no driver
or are we failing the migration?  There shouldn't be a requirement on
the state of the guest driver for a successful migration.  Thanks,

Alex

>  	ret = qm_set_regs(qm, vf_data);
>  	if (ret) {
>  		dev_err(dev, "set VF regs failed\n");
> @@ -1531,6 +1537,7 @@ 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);
>