linux-kernel - Re: [RFC PATCH v3 6/9] vfio/pci: export vfio_pci_setup

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Date:   Thu, 20 Feb 2020 14:00:13 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Yan Zhao <yan.y.zhao@...el.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        cohuck@...hat.com, zhenyuw@...ux.intel.com, zhi.a.wang@...el.com,
        kevin.tian@...el.com, shaopeng.he@...el.com, yi.l.liu@...el.com
Subject: Re: [RFC PATCH v3 6/9] vfio/pci: export vfio_pci_setup_barmap

On Tue, 11 Feb 2020 05:14:19 -0500
Yan Zhao <yan.y.zhao@...el.com> wrote:

> This allows vendor driver to read/write to bars directly which is useful
> in security checking condition.
> 
> Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
> ---
>  drivers/vfio/pci/vfio_pci_rdwr.c | 26 +++++++++++++-------------
>  include/linux/vfio.h             |  2 ++
>  2 files changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
> index a0ef1de4f74a..3ba85fb2af5b 100644
> --- a/drivers/vfio/pci/vfio_pci_rdwr.c
> +++ b/drivers/vfio/pci/vfio_pci_rdwr.c
> @@ -129,7 +129,7 @@ static ssize_t do_io_rw(void __iomem *io, char __user *buf,
>  	return done;
>  }
>  
> -static int vfio_pci_setup_barmap(struct vfio_pci_device *vdev, int bar)
> +void __iomem *vfio_pci_setup_barmap(struct vfio_pci_device *vdev, int bar)
>  {
>  	struct pci_dev *pdev = vdev->pdev;
>  	struct vfio_pci_device_private *priv = VDEV_TO_PRIV(vdev);
> @@ -137,22 +137,23 @@ static int vfio_pci_setup_barmap(struct vfio_pci_device *vdev, int bar)
>  	void __iomem *io;
>  
>  	if (priv->barmap[bar])
> -		return 0;
> +		return priv->barmap[bar];
>  
>  	ret = pci_request_selected_regions(pdev, 1 << bar, "vfio");
>  	if (ret)
> -		return ret;
> +		return NULL;
>  
>  	io = pci_iomap(pdev, bar, 0);
>  	if (!io) {
>  		pci_release_selected_regions(pdev, 1 << bar);
> -		return -ENOMEM;
> +		return NULL;
>  	}
>  
>  	priv->barmap[bar] = io;
>  
> -	return 0;
> +	return io;
>  }
> +EXPORT_SYMBOL_GPL(vfio_pci_setup_barmap);

This should instead become a vfio_pci_get_barmap() function that tests
for an optionally calls vfio_pci_setup_barmap before returning the
pointer.  I'm now willing to lose the better error returns in the
original.  Thanks,

Alex