linux-kernel - [PATCH RFC v4 1/4] iommu: Add set/unset_dev_user

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Date:   Mon, 8 May 2023 21:51:47 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     <jgg@...dia.com>, <kevin.tian@...el.com>
CC:     <robin.murphy@....com>, <eric.auger@...hat.com>,
        <yi.l.liu@...el.com>, <baolu.lu@...ux.intel.com>,
        <will@...nel.org>, <joro@...tes.org>,
        <shameerali.kolothum.thodi@...wei.com>, <jean-philippe@...aro.org>,
        <linux-arm-kernel@...ts.infradead.org>, <iommu@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH RFC v4 1/4] iommu: Add set/unset_dev_user_data ops

The device behind an IOMMU might be used in the user space by a VM. So, it
might have some user space data. For example, a device behind an SMMU has
a static stream ID. In a virtualization use case, both a host environment
and a guest environment have their own Stream IDs. A link (a lookup table)
between the physical Stream ID and the virtual (user) Stream ID is needed
when the host handles the user cache invalidation commands.

Add a pair of new ops to allow user space to forward user_data of a device
via iommufd, and a new dev_user_data_len for data structure sanity done by
the iommufd core.

Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
---
 include/linux/iommu.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 1131476017e2..1e1124f79b56 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -260,6 +260,15 @@ struct iommu_iotlb_gather {
  * @remove_dev_pasid: Remove any translation configurations of a specific
  *                    pasid, so that any DMA transactions with this pasid
  *                    will be blocked by the hardware.
+ * @set/unset_dev_user_data: set/unset an iommu specific device data from user
+ *                           space. The user device data info will be used by
+ *                           the driver to take care of user space requests.
+ *                           The device data structure must be defined in
+ *                           include/uapi/linux/iommufd.h.
+ * @dev_user_data_len: Length of the device data from user space (in bytes),
+ *                     simply the "sizeof" the data structure defined in the
+ *                     include/uapi/linux/iommufd.h. This is used by iommufd
+ *                     core to run a data length validation.
  * @hw_info_type: One of enum iommu_hw_info_type defined in
  *                include/uapi/linux/iommufd.h. It is used to tag the type
  *                of data returned by .hw_info callback. The drivers that
@@ -307,6 +316,10 @@ struct iommu_ops {
 	int (*def_domain_type)(struct device *dev);
 	void (*remove_dev_pasid)(struct device *dev, ioasid_t pasid);
 
+	int (*set_dev_user_data)(struct device *dev, const void *user_data);
+	void (*unset_dev_user_data)(struct device *dev);
+	size_t dev_user_data_len;
+
 	const struct iommu_domain_ops *default_domain_ops;
 	enum iommu_hw_info_type hw_info_type;
 	unsigned long long hwpt_type_bitmap;
-- 
2.40.1