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

Shameerali Kolothum Thodi
2025-02-26T09:26:09Z

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