linux-kernel - RE: [PATCH v4 5/5] hisi_acc_vfio_pci: bugfix live migration function without VF device driver

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Message-ID: <fa8cd8c1cdbe4849b445ffd8f4894515@huawei.com>
Date: Wed, 26 Feb 2025 09:26:07 +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 v4 5/5] hisi_acc_vfio_pci: bugfix live migration function
 without VF device driver



> -----Original Message-----
> From: liulongfang <liulongfang@...wei.com>
> Sent: Tuesday, February 25, 2025 6:28 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 v4 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.

May be rephrase:

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>
> ---
>  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 3f0bcd855839..77872fc4cd34 100644
> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> @@ -440,6 +440,7 @@ 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;
> @@ -466,6 +467,13 @@ 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);

We already have qm_wait_dev_not_ready() function that checks the QM_VF_STATE. 
Why can't we use that here?

Also we are getting this vf_qm_state already in vf_qm_state_save(). And you don't
seem to check the vf_qm_state in vf_qm_check_match(). So why it is read 
early in this function?


Thanks,
Shameer

> +	if (ret) {
> +		dev_err(dev, "failed to read QM_VF_STATE!\n");
> +		return ret;
> +	}
> +
>  	return 0;
>  }
> 
> @@ -505,6 +513,12 @@ 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;
> +	}
> +
>  	ret = qm_set_regs(qm, vf_data);
>  	if (ret) {
>  		dev_err(dev, "set VF regs failed\n");
> @@ -727,6 +741,9 @@ static int hisi_acc_vf_load_state(struct
> hisi_acc_vf_core_device *hisi_acc_vdev)
>  	struct hisi_acc_vf_migration_file *migf = hisi_acc_vdev-
> >resuming_migf;
>  	int ret;
> 
> +	if (hisi_acc_vdev->vf_qm_state != QM_READY)
> +		return 0;
> +
>  	/* Recover data to VF */
>  	ret = vf_qm_load_data(hisi_acc_vdev, migf);
>  	if (ret) {
> @@ -1530,6 +1547,7 @@ 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