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

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Message-ID: <20230605131009.6869-1-nipun.gupta@amd.com>
Date:   Mon, 5 Jun 2023 18:40:09 +0530
From:   Nipun Gupta <nipun.gupta@....com>
To:     <gregkh@...uxfoundation.org>, <alex.williamson@...hat.com>,
        <jgg@...pe.ca>, <linux-kernel@...r.kernel.org>
CC:     <git@....com>, <harpreet.anand@....com>,
        <pieter.jansen-van-vuuren@....com>, <nikhil.agarwal@....com>,
        <michal.simek@....com>, Nipun Gupta <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@redhat.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@amd.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