linux-kernel - RE: [RESEND PATCH] cdx: fix driver managed dma support

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Date:   Thu, 8 Jun 2023 04:37:07 +0000
From:   "Agarwal, Nikhil" <nikhil.agarwal@....com>
To:     "Gupta, Nipun" <Nipun.Gupta@....com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "jgg@...pe.ca" <jgg@...pe.ca>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "git (AMD-Xilinx)" <git@....com>,
        "Anand, Harpreet" <harpreet.anand@....com>,
        "Jansen Van Vuuren, Pieter" <pieter.jansen-van-vuuren@....com>,
        "Simek, Michal" <michal.simek@....com>,
        "Gupta, Nipun" <Nipun.Gupta@....com>
Subject: RE: [RESEND PATCH] cdx: fix driver managed dma support

Reviewed-by: Nikhil Agarwal <nikhil.agarwal@....com>

> -----Original Message-----
> From: Nipun Gupta <nipun.gupta@....com>
> Sent: Monday, June 5, 2023 6:40 PM
> To: gregkh@...uxfoundation.org; alex.williamson@...hat.com; jgg@...pe.ca;
> linux-kernel@...r.kernel.org
> Cc: git (AMD-Xilinx) <git@....com>; Anand, Harpreet
> <harpreet.anand@....com>; Jansen Van Vuuren, Pieter <pieter.jansen-van-
> vuuren@....com>; Agarwal, Nikhil <nikhil.agarwal@....com>; Simek,
> Michal <michal.simek@....com>; Gupta, Nipun <Nipun.Gupta@....com>
> Subject: [RESEND PATCH] cdx: fix driver managed dma support
> 
> The devices on cdx could be bound to drivers with the device DMA managed
> by kernel drivers or user-space applications.
> As multiple devices can be placed in the same IOMMU group, the DMA on
> these devices must either be entirely under kernel control or userspace
> control. Fix the CDX bus driver to acknowlege the driver_managed_dma flag
> and call the appropriate iommu APIs.
> 
> Fixes: 2959ab247061 ("cdx: add the cdx bus driver")
> Signed-off-by: Nipun Gupta <nipun.gupta@....com>
> Reported-by: Alex Williamson <alex.williamson@...hat.com>
> Closes:
> https://lore.kernel.org/lkml/20230524134831.28dc97e2.alex.williamson@re
> dhat.com/
> ---
> 
> I have resend this patch to include fixes, closes and reported by tags. We
> request that this fix be incorporated into the 6.4 release, along with the
> inclusion of CDX bus driver support.
> Original patch was sent at:
> https://lore.kernel.org/lkml/20230531114759.6173-1-
> nipun.gupta@....com/
> 
>  drivers/cdx/cdx.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/cdx/cdx.c b/drivers/cdx/cdx.c index
> dc74fae02a78..42bbe5ed370d 100644
> --- a/drivers/cdx/cdx.c
> +++ b/drivers/cdx/cdx.c
> @@ -63,6 +63,8 @@
>  #include <linux/mm.h>
>  #include <linux/xarray.h>
>  #include <linux/cdx/cdx_bus.h>
> +#include <linux/iommu.h>
> +#include <linux/dma-map-ops.h>
>  #include "cdx.h"
> 
>  /* Default DMA mask for devices on a CDX bus */ @@ -267,6 +269,7 @@
> static void cdx_shutdown(struct device *dev)
> 
>  static int cdx_dma_configure(struct device *dev)  {
> +	struct cdx_driver *cdx_drv = to_cdx_driver(dev->driver);
>  	struct cdx_device *cdx_dev = to_cdx_device(dev);
>  	u32 input_id = cdx_dev->req_id;
>  	int ret;
> @@ -277,9 +280,23 @@ static int cdx_dma_configure(struct device *dev)
>  		return ret;
>  	}
> 
> +	if (!ret && !cdx_drv->driver_managed_dma) {
> +		ret = iommu_device_use_default_domain(dev);
> +		if (ret)
> +			arch_teardown_dma_ops(dev);
> +	}
> +
>  	return 0;
>  }
> 
> +static void cdx_dma_cleanup(struct device *dev) {
> +	struct cdx_driver *cdx_drv = to_cdx_driver(dev->driver);
> +
> +	if (!cdx_drv->driver_managed_dma)
> +		iommu_device_unuse_default_domain(dev);
> +}
> +
>  /* show configuration fields */
>  #define cdx_config_attr(field, format_string)	\
>  static ssize_t	\
> @@ -503,6 +520,7 @@ struct bus_type cdx_bus_type = {
>  	.remove		= cdx_remove,
>  	.shutdown	= cdx_shutdown,
>  	.dma_configure	= cdx_dma_configure,
> +	.dma_cleanup	= cdx_dma_cleanup,
>  	.bus_groups	= cdx_bus_groups,
>  	.dev_groups	= cdx_dev_groups,
>  };
> --
> 2.17.1