linux-kernel - Re: [PATCH 2/2] vfio/fsl-mc: Add per device reset support

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Date:   Mon, 30 Aug 2021 12:42:05 +0300
From:   Laurentiu Tudor <laurentiu.tudor@....com>
To:     Diana Craciun <diana.craciun@....nxp.com>,
        linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        Alex Williamson <alex.williamson@...hat.com>,
        kvm@...r.kernel.org
Cc:     Li Yang <leoyang.li@....com>, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] vfio/fsl-mc: Add per device reset support



On 8/25/2021 12:05 PM, Diana Craciun wrote:
> Currently when a fsl-mc device is reset, the entire DPRC container
> is reset which is very inefficient because the devices within a
> container will be reset multiple times.
> Add support for individually resetting a device.
> 
> Signed-off-by: Diana Craciun <diana.craciun@....nxp.com>
> ---
>  drivers/vfio/fsl-mc/vfio_fsl_mc.c | 45 ++++++++++++++++++++-----------
>  1 file changed, 29 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/vfio/fsl-mc/vfio_fsl_mc.c b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> index 90cad109583b..46126d41dc32 100644
> --- a/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc.c
> @@ -155,6 +155,33 @@ static int vfio_fsl_mc_open(struct vfio_device *core_vdev)
>  	return ret;
>  }
>  
> +static int vfio_fsl_mc_reset_device(struct vfio_fsl_mc_device *vdev)
> +{
> +	struct fsl_mc_device *mc_dev = vdev->mc_dev;
> +	int ret = 0;
> +
> +	if (is_fsl_mc_bus_dprc(vdev->mc_dev)) {
> +		return dprc_reset_container(mc_dev->mc_io, 0,
> +					mc_dev->mc_handle,
> +					mc_dev->obj_desc.id,
> +					DPRC_RESET_OPTION_NON_RECURSIVE);
> +	} else {
> +		int err;
> +		u16 token;
> +
> +		err = fsl_mc_obj_open(mc_dev->mc_io, 0, mc_dev->obj_desc.id,
> +				      mc_dev->obj_desc.type,
> +				      &token);
> +		if (err)
> +			return err;
> +		ret = fsl_mc_obj_reset(mc_dev->mc_io, 0, token);
> +		err = fsl_mc_obj_close(mc_dev->mc_io, 0, token);
> +		if (err)
> +			return err;

Error handling here looks a bit atypical to me. Maybe something like
this, which will also get rid of the 2nd err var.

	{
		ret = fsl_mc_obj_open(...);
		if (ret)
			goto out;
		ret = fsl_mc_obj_reset(...);
		if (ret) {
			fsl_mc_obj_close(...);
			goto out;
		}
		ret = fsl_mc_obj_close(...);
	}

out:
	return ret;

---
Best Regards, Laurentiu

> +	}
> +	return ret;
> +}
> +
>  static void vfio_fsl_mc_release(struct vfio_device *core_vdev)
>  {
>  	struct vfio_fsl_mc_device *vdev =
> @@ -171,10 +198,7 @@ static void vfio_fsl_mc_release(struct vfio_device *core_vdev)
>  		vfio_fsl_mc_regions_cleanup(vdev);
>  
>  		/* reset the device before cleaning up the interrupts */
> -		ret = dprc_reset_container(mc_cont->mc_io, 0,
> -		      mc_cont->mc_handle,
> -			  mc_cont->obj_desc.id,
> -			  DPRC_RESET_OPTION_NON_RECURSIVE);
> +		ret = vfio_fsl_mc_reset_device(vdev);
>  
>  		if (ret) {
>  			dev_warn(&mc_cont->dev, "VFIO_FLS_MC: reset device has failed (%d)\n",
> @@ -302,18 +326,7 @@ static long vfio_fsl_mc_ioctl(struct vfio_device *core_vdev,
>  	}
>  	case VFIO_DEVICE_RESET:
>  	{
> -		int ret;
> -		struct fsl_mc_device *mc_dev = vdev->mc_dev;
> -
> -		/* reset is supported only for the DPRC */
> -		if (!is_fsl_mc_bus_dprc(mc_dev))
> -			return -ENOTTY;
> -
> -		ret = dprc_reset_container(mc_dev->mc_io, 0,
> -					   mc_dev->mc_handle,
> -					   mc_dev->obj_desc.id,
> -					   DPRC_RESET_OPTION_NON_RECURSIVE);
> -		return ret;
> +		return vfio_fsl_mc_reset_device(vdev);
>  
>  	}
>  	default:
>