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: <937a11b53cca42ef94d8383608a10f59@huawei.com>
Date: Tue, 15 Apr 2025 08:45:48 +0000
From: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>
To: liulongfang <liulongfang@...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



> -----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?

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