RE: [PATCH v2 5/5] hisi_acc_vfio_pci: bugfix live migration function without VF device driver

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>]

> -----Original Message-----
> From: liulongfang <liulongfang@huawei.com>
> Sent: Thursday, December 19, 2024 9:18 AM
> To: alex.williamson@redhat.com; jgg@nvidia.com; Shameerali Kolothum
> Thodi <shameerali.kolothum.thodi@huawei.com>; Jonathan Cameron
> <jonathan.cameron@huawei.com>
> Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org;
> linuxarm@openeuler.org; liulongfang <liulongfang@huawei.com>
> Subject: [PATCH v2 5/5] hisi_acc_vfio_pci: bugfix live migration function
> without VF device driver
> 
> If the driver of the VF device is not loaded in the Guest OS,
> then perform device data migration. The migrated data address 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.
> 
> Signed-off-by: Longfang Liu <liulongfang@huawei.com>

Why this doesn't need a Fixes tag?

> ---
>  drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> index 8d9e07ebf4fd..9a5f7e9bc695 100644
> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> @@ -436,6 +436,7 @@ static int vf_qm_get_match_data(struct
> hisi_acc_vf_core_device *hisi_acc_vdev,
>  				struct acc_vf_data *vf_data)
>  {
>  	struct hisi_qm *pf_qm = hisi_acc_vdev->pf_qm;
> +	struct hisi_qm *vf_qm = &hisi_acc_vdev->vf_qm;
>  	struct device *dev = &pf_qm->pdev->dev;
>  	int vf_id = hisi_acc_vdev->vf_id;
>  	int ret;
> @@ -460,6 +461,13 @@ static int vf_qm_get_match_data(struct
> hisi_acc_vf_core_device *hisi_acc_vdev,
>  		return ret;
>  	}
> 
> +	/* Get VF driver insmod state */
> +	ret = qm_read_regs(vf_qm, QM_VF_STATE, &vf_data->vf_qm_state,
> 1);
> +	if (ret) {
> +		dev_err(dev, "failed to read QM_VF_STATE!\n");
> +		return ret;
> +	}
> +
>  	return 0;
>  }
> 
> @@ -499,6 +507,12 @@ 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;
> +	}
> +

So this is to cover the corner case where the Guest has loaded the driver
(QM_READY set) but not configured the DMA address? When this will happen?
I thought we are setting QM_READY in guest after all configurations.

Thanks,
Shameer