linux-kernel - Re: [PATCH v2] drm/i915/gvt: throw error on unhandled vfio ioctls

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Date:   Wed, 21 Mar 2018 06:58:04 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     intel-gvt-dev@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, stable@...r.kernel.org,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/i915/gvt: throw error on unhandled vfio ioctls

On Wed, 21 Mar 2018 10:08:03 +0100
Gerd Hoffmann <kraxel@...hat.com> wrote:

> On unknown/unhandled ioctls the driver should return an error, so
> userspace knows it tried to use something unsupported.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
> ---
>  drivers/gpu/drm/i915/gvt/kvmgt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index 021f722e24..be881d53c2 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -1284,7 +1284,7 @@ static long intel_vgpu_ioctl(struct mdev_device *mdev, unsigned int cmd,
>  
>  	}
>  
> -	return 0;
> +	return -EINVAL;
>  }
>  
>  static ssize_t

Absolutely, but I'd prefer to continue the standard behavior among
other vfio drivers, and adopted from elsewhere in the kernel, to use
-ENOTTY for an unhandled ioctl, reserving -EINVAL as an error in
options for a supported ioctl.  Thanks,

Alex