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

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Date:   Sun, 27 Sep 2020 07:23:47 +0000
From:   Sherry Sun <sherry.sun@....com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "sudeep.dutt@...el.com" <sudeep.dutt@...el.com>,
        "ashutosh.dixit@...el.com" <ashutosh.dixit@...el.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "wang.yi59@....com.cn" <wang.yi59@....com.cn>,
        "rikard.falkeborn@...il.com" <rikard.falkeborn@...il.com>,
        "lee.jones@...aro.org" <lee.jones@...aro.org>,
        "mst@...hat.com" <mst@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH 3/5] misc: vop: simply return the saved dma address
 instead of virt_to_phys

Hi Greg,

> -----Original Message-----
> 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.
> 

Do you mean that we should avoid to use WARN_ON here?

> > +			return -1;
> 
> Use a real error value, do not make them up.

Ok, will change it. Thanks.

Best regards
Sherry

> 
> thanks,
> 
> greg k-h