Re: [PATCH 1/4] hisi_acc_vfio_pci: fix VF reset timeout issue

[Alex Williamson <alex@shazbot.org>]

On Sun, 4 Jan 2026 15:07:03 +0800
Longfang Liu <liulongfang@huawei.com> wrote:

> From: Weili Qian <qianweili@huawei.com>
> 
> If device error occurs during live migration, qemu will
> reset the VF. At this time, VF reset and device reset are performed
> simultaneously. The VF reset will timeout. Therefore, the QM_RESETTING
> flag is used to ensure that VF reset and device reset are performed
> serially.
> 
> Fixes: b0eed085903e ("hisi_acc_vfio_pci: Add support for VFIO live migration")
> Signed-off-by: Weili Qian <qianweili@huawei.com>
> ---
>  .../vfio/pci/hisilicon/hisi_acc_vfio_pci.c    | 24 +++++++++++++++++++
>  .../vfio/pci/hisilicon/hisi_acc_vfio_pci.h    |  2 ++
>  2 files changed, 26 insertions(+)
> 
> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> index fe2ffcd00d6e..d55365b21f78 100644
> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> @@ -1188,14 +1188,37 @@ hisi_acc_vfio_pci_get_device_state(struct vfio_device *vdev,
>  	return 0;
>  }
>  
> +static void hisi_acc_vf_pci_reset_prepare(struct pci_dev *pdev)
> +{
> +	struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_drvdata(pdev);
> +	struct hisi_qm *qm = hisi_acc_vdev->pf_qm;
> +	struct device *dev = &qm->pdev->dev;
> +	u32 delay = 0;
> +
> +	/* All reset requests need to be queued for processing */
> +	while (test_and_set_bit(QM_RESETTING, &qm->misc_ctl)) {
> +		msleep(1);
> +		if (++delay > QM_RESET_WAIT_TIMEOUT) {
> +			dev_err(dev, "reset prepare failed\n");
> +			return;
> +		}
> +	}
> +
> +	hisi_acc_vdev->set_reset_flag = true;
> +}
> +
>  static void hisi_acc_vf_pci_aer_reset_done(struct pci_dev *pdev)
>  {
>  	struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_drvdata(pdev);
> +	struct hisi_qm *qm = hisi_acc_vdev->pf_qm;
>  
>  	if (hisi_acc_vdev->core_device.vdev.migration_flags !=
>  				VFIO_MIGRATION_STOP_COPY)
>  		return;
>  
> +	if (hisi_acc_vdev->set_reset_flag)
> +		clear_bit(QM_RESETTING, &qm->misc_ctl);


.reset_prepare sets QM_RESETTING unconditionally, .reset_done clears
QM_RESETTING conditionally based on the migration state.  In 2/ this
becomes conditional on the device supporting migration ops.  Doesn't
this enable a scenario where a device that does not support migration
puts QM_RESETTING into an inconsistent state that is never cleared?
Should the clear_bit() occur before the migration state/capability
check?

Thanks,
Alex

> +
>  	mutex_lock(&hisi_acc_vdev->state_mutex);
>  	hisi_acc_vf_reset(hisi_acc_vdev);
>  	mutex_unlock(&hisi_acc_vdev->state_mutex);
> @@ -1746,6 +1769,7 @@ static const struct pci_device_id hisi_acc_vfio_pci_table[] = {
>  MODULE_DEVICE_TABLE(pci, hisi_acc_vfio_pci_table);
>  
>  static const struct pci_error_handlers hisi_acc_vf_err_handlers = {
> +	.reset_prepare = hisi_acc_vf_pci_reset_prepare,
>  	.reset_done = hisi_acc_vf_pci_aer_reset_done,
>  	.error_detected = vfio_pci_core_aer_err_detected,
>  };
> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> index cd55eba64dfb..a3d91a31e3d8 100644
> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> @@ -27,6 +27,7 @@
>  
>  #define ERROR_CHECK_TIMEOUT		100
>  #define CHECK_DELAY_TIME		100
> +#define QM_RESET_WAIT_TIMEOUT  60000
>  
>  #define QM_SQC_VFT_BASE_SHIFT_V2	28
>  #define QM_SQC_VFT_BASE_MASK_V2		GENMASK(15, 0)
> @@ -128,6 +129,7 @@ struct hisi_acc_vf_migration_file {
>  struct hisi_acc_vf_core_device {
>  	struct vfio_pci_core_device core_device;
>  	u8 match_done;
> +	bool set_reset_flag;
>  	/*
>  	 * io_base is only valid when dev_opened is true,
>  	 * which is protected by open_mutex.