linux-kernel - Re: [PATCH v8 9/9] hisi_acc_vfio_pci: Use its own PCI reset

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Date:   Tue, 8 Mar 2022 09:14:11 +0800
From:   liulongfang <liulongfang@...wei.com>
To:     Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
        <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-crypto@...r.kernel.org>
CC:     <linux-pci@...r.kernel.org>, <alex.williamson@...hat.com>,
        <jgg@...dia.com>, <cohuck@...hat.com>, <mgurtovoy@...dia.com>,
        <yishaih@...dia.com>, <linuxarm@...wei.com>,
        <prime.zeng@...ilicon.com>, <jonathan.cameron@...wei.com>,
        <wangzhou1@...ilicon.com>
Subject: Re: [PATCH v8 9/9] hisi_acc_vfio_pci: Use its own PCI reset_done
 error handler

On 2022/3/4 7:01, Shameer Kolothum wrote:
> Register private handler for pci_error_handlers.reset_done and update
> state accordingly.
> 
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
> ---
>  .../vfio/pci/hisilicon/hisi_acc_vfio_pci.c    | 57 ++++++++++++++++++-
>  .../vfio/pci/hisilicon/hisi_acc_vfio_pci.h    |  4 +-
>  2 files changed, 57 insertions(+), 4 deletions(-)
> 
Reviewed-by: Longfang Liu <liulongfang@...wei.com>

Thanks,
Longfang
> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> index aa2e4b6bf598..53e4c5cb3a71 100644
> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> @@ -625,6 +625,27 @@ static void hisi_acc_vf_disable_fds(struct hisi_acc_vf_core_device *hisi_acc_vde
>  	}
>  }
>  
> +/*
> + * This function is called in all state_mutex unlock cases to
> + * handle a 'deferred_reset' if exists.
> + */
> +static void
> +hisi_acc_vf_state_mutex_unlock(struct hisi_acc_vf_core_device *hisi_acc_vdev)
> +{
> +again:
> +	spin_lock(&hisi_acc_vdev->reset_lock);
> +	if (hisi_acc_vdev->deferred_reset) {
> +		hisi_acc_vdev->deferred_reset = false;
> +		spin_unlock(&hisi_acc_vdev->reset_lock);
> +		hisi_acc_vdev->vf_qm_state = QM_NOT_READY;
> +		hisi_acc_vdev->mig_state = VFIO_DEVICE_STATE_RUNNING;
> +		hisi_acc_vf_disable_fds(hisi_acc_vdev);
> +		goto again;
> +	}
> +	mutex_unlock(&hisi_acc_vdev->state_mutex);
> +	spin_unlock(&hisi_acc_vdev->reset_lock);
> +}
> +
>  static void hisi_acc_vf_start_device(struct hisi_acc_vf_core_device *hisi_acc_vdev)
>  {
>  	struct hisi_qm *vf_qm = &hisi_acc_vdev->vf_qm;
> @@ -921,7 +942,7 @@ hisi_acc_vfio_pci_set_device_state(struct vfio_device *vdev,
>  			break;
>  		}
>  	}
> -	mutex_unlock(&hisi_acc_vdev->state_mutex);
> +	hisi_acc_vf_state_mutex_unlock(hisi_acc_vdev);
>  	return res;
>  }
>  
> @@ -934,10 +955,35 @@ hisi_acc_vfio_pci_get_device_state(struct vfio_device *vdev,
>  
>  	mutex_lock(&hisi_acc_vdev->state_mutex);
>  	*curr_state = hisi_acc_vdev->mig_state;
> -	mutex_unlock(&hisi_acc_vdev->state_mutex);
> +	hisi_acc_vf_state_mutex_unlock(hisi_acc_vdev);
>  	return 0;
>  }
>  
> +static void hisi_acc_vf_pci_aer_reset_done(struct pci_dev *pdev)
> +{
> +	struct hisi_acc_vf_core_device *hisi_acc_vdev = dev_get_drvdata(&pdev->dev);
> +
> +	if (hisi_acc_vdev->core_device.vdev.migration_flags !=
> +				VFIO_MIGRATION_STOP_COPY)
> +		return;
> +
> +	/*
> +	 * As the higher VFIO layers are holding locks across reset and using
> +	 * those same locks with the mm_lock we need to prevent ABBA deadlock
> +	 * with the state_mutex and mm_lock.
> +	 * In case the state_mutex was taken already we defer the cleanup work
> +	 * to the unlock flow of the other running context.
> +	 */
> +	spin_lock(&hisi_acc_vdev->reset_lock);
> +	hisi_acc_vdev->deferred_reset = true;
> +	if (!mutex_trylock(&hisi_acc_vdev->state_mutex)) {
> +		spin_unlock(&hisi_acc_vdev->reset_lock);
> +		return;
> +	}
> +	spin_unlock(&hisi_acc_vdev->reset_lock);
> +	hisi_acc_vf_state_mutex_unlock(hisi_acc_vdev);
> +}
> +
>  static int hisi_acc_vf_qm_init(struct hisi_acc_vf_core_device *hisi_acc_vdev)
>  {
>  	struct vfio_pci_core_device *vdev = &hisi_acc_vdev->core_device;
> @@ -1252,12 +1298,17 @@ 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_done = hisi_acc_vf_pci_aer_reset_done,
> +	.error_detected = vfio_pci_core_aer_err_detected,
> +};
> +
>  static struct pci_driver hisi_acc_vfio_pci_driver = {
>  	.name = KBUILD_MODNAME,
>  	.id_table = hisi_acc_vfio_pci_table,
>  	.probe = hisi_acc_vfio_pci_probe,
>  	.remove = hisi_acc_vfio_pci_remove,
> -	.err_handler = &vfio_pci_core_err_handlers,
> +	.err_handler = &hisi_acc_vf_err_handlers,
>  };
>  
>  module_pci_driver(hisi_acc_vfio_pci_driver);
> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> index 1c7d75408790..5494f4983bbe 100644
> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> @@ -98,6 +98,7 @@ struct hisi_acc_vf_migration_file {
>  
>  struct hisi_acc_vf_core_device {
>  	struct vfio_pci_core_device core_device;
> +	u8 deferred_reset:1;
>  	/* for migration state */
>  	struct mutex state_mutex;
>  	enum vfio_device_mig_state mig_state;
> @@ -107,7 +108,8 @@ struct hisi_acc_vf_core_device {
>  	struct hisi_qm vf_qm;
>  	u32 vf_qm_state;
>  	int vf_id;
> -
> +	/* for reset handler */
> +	spinlock_t reset_lock;
>  	struct hisi_acc_vf_migration_file *resuming_migf;
>  	struct hisi_acc_vf_migration_file *saving_migf;
>  };
>