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Message-ID: <3ab48d4978318938911d91833654b296947668ad.1724777091.git.nicolinc@nvidia.com>
Date: Tue, 27 Aug 2024 10:02:06 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: <jgg@...dia.com>, <kevin.tian@...el.com>, <will@...nel.org>
CC: <joro@...tes.org>, <suravee.suthikulpanit@....com>,
	<robin.murphy@....com>, <dwmw2@...radead.org>, <baolu.lu@...ux.intel.com>,
	<shuah@...nel.org>, <linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kselftest@...r.kernel.org>,
	<eric.auger@...hat.com>, <jean-philippe@...aro.org>, <mdf@...nel.org>,
	<mshavit@...gle.com>, <shameerali.kolothum.thodi@...wei.com>,
	<smostafa@...gle.com>, <yi.l.liu@...el.com>
Subject: [PATCH v1 04/10] iommufd/viommu: Allow drivers to control vdev_id lifecycle

The iommufd core provides a lookup helper for an IOMMU driver to find a
device pointer by device's per-viommu virtual ID. Yet a driver may need
an inverted lookup to find a device's per-viommu virtual ID by a device
pointer, e.g. when reporting virtual IRQs/events back to the user space.
In this case, it'd be unsafe for iommufd core to do an inverted lookup,
as the driver can't track the lifecycle of a viommu object or a vdev_id
object.

Meanwhile, some HW can even support virtual device ID lookup by its HW-
accelerated virtualization feature. E.g. Tegra241 CMDQV HW supports to
execute vanilla guest-issued SMMU commands containing virtual Stream ID
but requires software to configure a link between virtual Stream ID and
physical Stream ID via HW registers. So not only the iommufd core needs
a vdev_id lookup table, drivers will want one too.

Given the two justifications above, it's the best practice to provide a
a pair of set_vdev_id/unset_vdev_id ops in the viommu ops, so a driver
can implement them to control a vdev_id's lifecycle, and configure the
HW properly if required.

Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
---
 drivers/iommu/iommufd/device.c          |  2 ++
 drivers/iommu/iommufd/iommufd_private.h |  6 ------
 drivers/iommu/iommufd/viommu.c          | 23 +++++++++++++++++++----
 include/linux/iommufd.h                 | 13 +++++++++++++
 4 files changed, 34 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 3ad759971b32..01bb5c9f415b 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -145,6 +145,8 @@ void iommufd_device_destroy(struct iommufd_object *obj)
 		old = xa_cmpxchg(&viommu->vdev_ids, vdev_id->id, vdev_id, NULL,
 				 GFP_KERNEL);
 		WARN_ON(old != vdev_id);
+		if (vdev_id->viommu->ops && vdev_id->viommu->ops->unset_vdev_id)
+			vdev_id->viommu->ops->unset_vdev_id(vdev_id);
 		kfree(vdev_id);
 		idev->vdev_id = NULL;
 	}
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index be1f1813672e..4cb1555991b8 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -621,12 +621,6 @@ struct iommufd_viommu {
 	unsigned int type;
 };
 
-struct iommufd_vdev_id {
-	struct iommufd_viommu *viommu;
-	struct iommufd_device *idev;
-	u64 id;
-};
-
 static inline struct iommufd_viommu *
 iommufd_get_viommu(struct iommufd_ucmd *ucmd, u32 id)
 {
diff --git a/drivers/iommu/iommufd/viommu.c b/drivers/iommu/iommufd/viommu.c
index 9adc9c62ada9..b1eb900b7fbf 100644
--- a/drivers/iommu/iommufd/viommu.c
+++ b/drivers/iommu/iommufd/viommu.c
@@ -13,6 +13,8 @@ void iommufd_viommu_destroy(struct iommufd_object *obj)
 
 	xa_for_each(&viommu->vdev_ids, index, vdev_id) {
 		/* Unlocked since there should be no race in a destroy() */
+		if (viommu->ops && viommu->ops->unset_vdev_id)
+			viommu->ops->unset_vdev_id(vdev_id);
 		vdev_id->idev->vdev_id = NULL;
 		kfree(vdev_id);
 	}
@@ -116,10 +118,18 @@ int iommufd_viommu_set_vdev_id(struct iommufd_ucmd *ucmd)
 		goto out_unlock_igroup;
 	}
 
-	vdev_id = kzalloc(sizeof(*vdev_id), GFP_KERNEL);
-	if (!vdev_id) {
-		rc = -ENOMEM;
-		goto out_unlock_igroup;
+	if (viommu->ops && viommu->ops->set_vdev_id) {
+		vdev_id = viommu->ops->set_vdev_id(viommu, idev->dev, cmd->vdev_id);
+		if (IS_ERR(vdev_id)) {
+			rc = PTR_ERR(vdev_id);
+			goto out_unlock_igroup;
+		}
+	} else {
+		vdev_id = kzalloc(sizeof(*vdev_id), GFP_KERNEL);
+		if (!vdev_id) {
+			rc = -ENOMEM;
+			goto out_unlock_igroup;
+		}
 	}
 
 	vdev_id->idev = idev;
@@ -137,6 +147,8 @@ int iommufd_viommu_set_vdev_id(struct iommufd_ucmd *ucmd)
 	goto out_unlock_igroup;
 
 out_free:
+	if (viommu->ops && viommu->ops->unset_vdev_id)
+		viommu->ops->unset_vdev_id(vdev_id);
 	kfree(vdev_id);
 out_unlock_igroup:
 	mutex_unlock(&idev->igroup->lock);
@@ -185,6 +197,9 @@ int iommufd_viommu_unset_vdev_id(struct iommufd_ucmd *ucmd)
 		rc = xa_err(old);
 		goto out_unlock_igroup;
 	}
+
+	if (viommu->ops && viommu->ops->unset_vdev_id)
+		viommu->ops->unset_vdev_id(old);
 	kfree(old);
 	idev->vdev_id = NULL;
 
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index f7c265c6de7c..c89583c7c792 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -56,8 +56,18 @@ void iommufd_access_detach(struct iommufd_access *access);
 
 void iommufd_ctx_get(struct iommufd_ctx *ictx);
 
+struct iommufd_vdev_id {
+	struct iommufd_viommu *viommu;
+	struct iommufd_device *idev;
+	u64 id;
+};
+
 /**
  * struct iommufd_viommu_ops - viommu specific operations
+ * @set_vdev_id: Set a virtual device id for a device assigned to a viommu.
+ *               Driver allocates an iommufd_vdev_id and return its pointer.
+ * @unset_vdev_id: Unset a virtual device id for a device assigned to a viommu.
+ *                 iommufd core frees the memory pointed by an iommufd_vdev_id.
  * @cache_invalidate: Flush hardware cache used by a viommu. It can be used for
  *                    any IOMMU hardware specific cache as long as a viommu has
  *                    enough information to identify it: for example, a VMID or
@@ -69,6 +79,9 @@ void iommufd_ctx_get(struct iommufd_ctx *ictx);
  *                    include/uapi/linux/iommufd.h
  */
 struct iommufd_viommu_ops {
+	struct iommufd_vdev_id *(*set_vdev_id)(struct iommufd_viommu *viommu,
+					       struct device *dev, u64 id);
+	void (*unset_vdev_id)(struct iommufd_vdev_id *vdev_id);
 	int (*cache_invalidate)(struct iommufd_viommu *viommu,
 				struct iommu_user_data_array *array);
 };
-- 
2.43.0


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