netdev - Re: [PATCH V2 mlx5-next 14/14] vfio/mlx5: Use its own PCI reset

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Date:   Tue, 19 Oct 2021 12:55:13 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Yishai Hadas <yishaih@...dia.com>
Cc:     <bhelgaas@...gle.com>, <jgg@...dia.com>, <saeedm@...dia.com>,
        <linux-pci@...r.kernel.org>, <kvm@...r.kernel.org>,
        <netdev@...r.kernel.org>, <kuba@...nel.org>, <leonro@...dia.com>,
        <kwankhede@...dia.com>, <mgurtovoy@...dia.com>, <maorg@...dia.com>
Subject: Re: [PATCH V2 mlx5-next 14/14] vfio/mlx5: Use its own PCI
 reset_done error handler

On Tue, 19 Oct 2021 13:58:38 +0300
Yishai Hadas <yishaih@...dia.com> wrote:

> Register its own handler for pci_error_handlers.reset_done and update
> state accordingly.
> 
> Signed-off-by: Yishai Hadas <yishaih@...dia.com>
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> ---
>  drivers/vfio/pci/mlx5/main.c | 33 ++++++++++++++++++++++++++++++++-
>  1 file changed, 32 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/pci/mlx5/main.c b/drivers/vfio/pci/mlx5/main.c
> index 621b7fc60544..b759c6e153b6 100644
> --- a/drivers/vfio/pci/mlx5/main.c
> +++ b/drivers/vfio/pci/mlx5/main.c
> @@ -58,6 +58,7 @@ struct mlx5vf_pci_core_device {
>  	/* protect migartion state */
>  	struct mutex state_mutex;
>  	struct mlx5vf_pci_migration_info vmig;
> +	struct work_struct work;
>  };
>  
>  static int mlx5vf_pci_unquiesce_device(struct mlx5vf_pci_core_device *mvdev)
> @@ -615,6 +616,27 @@ static const struct vfio_device_ops mlx5vf_pci_ops = {
>  	.match = vfio_pci_core_match,
>  };
>  
> +static void mlx5vf_reset_work_handler(struct work_struct *work)
> +{
> +	struct mlx5vf_pci_core_device *mvdev =
> +		container_of(work, struct mlx5vf_pci_core_device, work);
> +
> +	mutex_lock(&mvdev->state_mutex);
> +	mlx5vf_reset_mig_state(mvdev);

I see this calls mlx5vf_reset_vhca_state() but how does that unfreeze
and unquiesce the device as necessary to get back to _RUNNING?

> +	mvdev->vmig.vfio_dev_state = VFIO_DEVICE_STATE_RUNNING;
> +	mutex_unlock(&mvdev->state_mutex);
> +}
> +
> +static void mlx5vf_pci_aer_reset_done(struct pci_dev *pdev)
> +{
> +	struct mlx5vf_pci_core_device *mvdev = dev_get_drvdata(&pdev->dev);
> +
> +	if (!mvdev->migrate_cap)
> +		return;
> +
> +	schedule_work(&mvdev->work);

This seems troublesome, how long does userspace poll the device state
after reset to get back to _RUNNING?  Seems we at least need a
flush_work() call when userspace reads the device state.  Thanks,

Alex

> +}
> +
>  static int mlx5vf_pci_probe(struct pci_dev *pdev,
>  			    const struct pci_device_id *id)
>  {
> @@ -634,6 +656,8 @@ static int mlx5vf_pci_probe(struct pci_dev *pdev,
>  			if (MLX5_CAP_GEN(mdev, migration)) {
>  				mvdev->migrate_cap = 1;
>  				mutex_init(&mvdev->state_mutex);
> +				INIT_WORK(&mvdev->work,
> +					  mlx5vf_reset_work_handler);
>  			}
>  			mlx5_vf_put_core_dev(mdev);
>  		}
> @@ -656,6 +680,8 @@ static void mlx5vf_pci_remove(struct pci_dev *pdev)
>  {
>  	struct mlx5vf_pci_core_device *mvdev = dev_get_drvdata(&pdev->dev);
>  
> +	if (mvdev->migrate_cap)
> +		cancel_work_sync(&mvdev->work);
>  	vfio_pci_core_unregister_device(&mvdev->core_device);
>  	vfio_pci_core_uninit_device(&mvdev->core_device);
>  	kfree(mvdev);
> @@ -668,12 +694,17 @@ static const struct pci_device_id mlx5vf_pci_table[] = {
>  
>  MODULE_DEVICE_TABLE(pci, mlx5vf_pci_table);
>  
> +const struct pci_error_handlers mlx5vf_err_handlers = {
> +	.reset_done = mlx5vf_pci_aer_reset_done,
> +	.error_detected = vfio_pci_aer_err_detected,
> +};
> +
>  static struct pci_driver mlx5vf_pci_driver = {
>  	.name = KBUILD_MODNAME,
>  	.id_table = mlx5vf_pci_table,
>  	.probe = mlx5vf_pci_probe,
>  	.remove = mlx5vf_pci_remove,
> -	.err_handler = &vfio_pci_core_err_handlers,
> +	.err_handler = &mlx5vf_err_handlers,
>  };
>  
>  static void __exit mlx5vf_pci_cleanup(void)