linux-kernel - Re: [PATCH 3/5] misc: vop: simply return the saved dma address instead of virt_to

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Message-ID: <20200925121729.GC2680110@kroah.com>
Date:   Fri, 25 Sep 2020 14:17:29 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Sherry Sun <sherry.sun@....com>
Cc:     sudeep.dutt@...el.com, ashutosh.dixit@...el.com, arnd@...db.de,
        wang.yi59@....com.cn, huang.zijiang@....com.cn,
        rikard.falkeborn@...il.com, lee.jones@...aro.org, mst@...hat.com,
        linux-kernel@...r.kernel.org, linux-imx@....com
Subject: Re: [PATCH 3/5] misc: vop: simply return the saved dma address
 instead of virt_to_phys

On Fri, Sep 25, 2020 at 03:26:28PM +0800, Sherry Sun wrote:
> For noncoherent platform, the device page and vring should allocated by
> dma_alloc_coherent, when user space wants to get its physical address,
> virt_to_phys cannot be used, should simply return the saved device page
> dma address by get_dp_dma callback and the vring dma address saved
> in mic_vqconfig.
> 
> Signed-off-by: Sherry Sun <sherry.sun@....com>
> Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> ---
>  drivers/misc/mic/bus/vop_bus.h    |  2 ++
>  drivers/misc/mic/host/mic_boot.c  |  8 ++++++++
>  drivers/misc/mic/vop/vop_vringh.c | 12 ++++++++++--
>  3 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/misc/mic/bus/vop_bus.h b/drivers/misc/mic/bus/vop_bus.h
> index 4fa02808c1e2..d891eacae358 100644
> --- a/drivers/misc/mic/bus/vop_bus.h
> +++ b/drivers/misc/mic/bus/vop_bus.h
> @@ -75,6 +75,7 @@ struct vop_driver {
>   *                 node to add/remove/configure virtio devices.
>   * @get_dp: Get access to the virtio device page used by the self
>   *          node to add/remove/configure virtio devices.
> + * @get_dp_dma: Get dma address of the virtio device page.
>   * @send_intr: Send an interrupt to the peer node on a specified doorbell.
>   * @remap: Map a buffer with the specified DMA address and length.
>   * @unmap: Unmap a buffer previously mapped.
> @@ -92,6 +93,7 @@ struct vop_hw_ops {
>  	void (*ack_interrupt)(struct vop_device *vpdev, int num);
>  	void __iomem * (*get_remote_dp)(struct vop_device *vpdev);
>  	void * (*get_dp)(struct vop_device *vpdev);
> +	dma_addr_t (*get_dp_dma)(struct vop_device *vpdev);
>  	void (*send_intr)(struct vop_device *vpdev, int db);
>  	void __iomem * (*remap)(struct vop_device *vpdev,
>  				  dma_addr_t pa, size_t len);
> diff --git a/drivers/misc/mic/host/mic_boot.c b/drivers/misc/mic/host/mic_boot.c
> index fb5b3989753d..ced03662cd8f 100644
> --- a/drivers/misc/mic/host/mic_boot.c
> +++ b/drivers/misc/mic/host/mic_boot.c
> @@ -88,6 +88,13 @@ static void *__mic_get_dp(struct vop_device *vpdev)
>  	return mdev->dp;
>  }
>  
> +static dma_addr_t __mic_get_dp_dma(struct vop_device *vpdev)
> +{
> +	struct mic_device *mdev = vpdev_to_mdev(&vpdev->dev);
> +
> +	return mdev->dp_dma_addr;
> +}
> +
>  static void __iomem *__mic_get_remote_dp(struct vop_device *vpdev)
>  {
>  	return NULL;
> @@ -119,6 +126,7 @@ static struct vop_hw_ops vop_hw_ops = {
>  	.ack_interrupt = __mic_ack_interrupt,
>  	.next_db = __mic_next_db,
>  	.get_dp = __mic_get_dp,
> +	.get_dp_dma = __mic_get_dp_dma,
>  	.get_remote_dp = __mic_get_remote_dp,
>  	.send_intr = __mic_send_intr,
>  	.remap = __mic_ioremap,
> diff --git a/drivers/misc/mic/vop/vop_vringh.c b/drivers/misc/mic/vop/vop_vringh.c
> index fc8d8ff9ded3..aa2dd240c11e 100644
> --- a/drivers/misc/mic/vop/vop_vringh.c
> +++ b/drivers/misc/mic/vop/vop_vringh.c
> @@ -1076,6 +1076,7 @@ vop_query_offset(struct vop_vdev *vdev, unsigned long offset,
>  		 unsigned long *size, unsigned long *pa)
>  {
>  	struct vop_device *vpdev = vdev->vpdev;
> +	struct mic_vqconfig *vqconfig = mic_vq_config(vdev->dd);
>  	unsigned long start = MIC_DP_SIZE;
>  	int i;
>  
> @@ -1088,7 +1089,14 @@ vop_query_offset(struct vop_vdev *vdev, unsigned long offset,
>  	 * ....
>  	 */
>  	if (!offset) {
> -		*pa = virt_to_phys(vpdev->hw_ops->get_dp(vpdev));
> +		if (vpdev->hw_ops->get_dp_dma)
> +			*pa = vpdev->hw_ops->get_dp_dma(vpdev);
> +		else {
> +			dev_err(vop_dev(vdev), "can't get device page physical address\n");
> +			WARN_ON(1);

Don't crash kernels that have panic_on_warn set for things you can
recover from.

> +			return -1;

Use a real error value, do not make them up.

thanks,

greg k-h