[PATCH v2 01/40] iommu: Introduce Shared Virtual Addressing API

[Jean-Philippe Brucker <jean-philippe.brucker-5wv7dgnIgG8@public.gmane.org>]

Shared Virtual Addressing (SVA) provides a way for device drivers to bind
process address spaces to devices. This requires the IOMMU to support page
table format and features compatible with the CPUs, and usually requires
the system to support I/O Page Faults (IOPF) and Process Address Space ID
(PASID). When all of these are available, DMA can access virtual addresses
of a process. A PASID is allocated for each process, and the device driver
programs it into the device in an implementation-specific way.

Add a new API for sharing process page tables with devices. Introduce two
IOMMU operations, sva_device_init() and sva_device_shutdown(), that
prepare the IOMMU driver for SVA. For example allocate PASID tables and
fault queues. Subsequent patches will implement the bind() and unbind()
operations.

Support for I/O Page Faults will be added in a later patch using a new
feature bit (IOMMU_SVA_FEAT_IOPF). With the current API users must pin
down all shared mappings. Other feature bits that may be added in the
future are IOMMU_SVA_FEAT_PRIVATE, to support private PASID address
spaces, and IOMMU_SVA_FEAT_NO_PASID, to bind the whole device address
space to a process.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker-5wv7dgnIgG8@public.gmane.org>

---
v1->v2:
* Add sva_param structure to iommu_param
* CONFIG option is only selectable by IOMMU drivers
---
 drivers/iommu/Kconfig     |   4 ++
 drivers/iommu/Makefile    |   1 +
 drivers/iommu/iommu-sva.c | 110 ++++++++++++++++++++++++++++++++++++++
 include/linux/iommu.h     |  32 +++++++++++
 4 files changed, 147 insertions(+)
 create mode 100644 drivers/iommu/iommu-sva.c

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 7564237f788d..cca8e06903c7 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -74,6 +74,10 @@ config IOMMU_DMA
 	select IOMMU_IOVA
 	select NEED_SG_DMA_LENGTH
 
+config IOMMU_SVA
+	bool
+	select IOMMU_API
+
 config FSL_PAMU
 	bool "Freescale IOMMU support"
 	depends on PCI
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index 1fb695854809..1dbcc89ebe4c 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -3,6 +3,7 @@ obj-$(CONFIG_IOMMU_API) += iommu.o
 obj-$(CONFIG_IOMMU_API) += iommu-traces.o
 obj-$(CONFIG_IOMMU_API) += iommu-sysfs.o
 obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
+obj-$(CONFIG_IOMMU_SVA) += iommu-sva.o
 obj-$(CONFIG_IOMMU_IO_PGTABLE) += io-pgtable.o
 obj-$(CONFIG_IOMMU_IO_PGTABLE_ARMV7S) += io-pgtable-arm-v7s.o
 obj-$(CONFIG_IOMMU_IO_PGTABLE_LPAE) += io-pgtable-arm.o
diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
new file mode 100644
index 000000000000..8b4afb7c63ae
--- /dev/null
+++ b/drivers/iommu/iommu-sva.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Manage PASIDs and bind process address spaces to devices.
+ *
+ * Copyright (C) 2018 ARM Ltd.
+ */
+
+#include <linux/iommu.h>
+#include <linux/slab.h>
+
+/**
+ * iommu_sva_device_init() - Initialize Shared Virtual Addressing for a device
+ * @dev: the device
+ * @features: bitmask of features that need to be initialized
+ * @max_pasid: max PASID value supported by the device
+ *
+ * Users of the bind()/unbind() API must call this function to initialize all
+ * features required for SVA.
+ *
+ * The device must support multiple address spaces (e.g. PCI PASID). By default
+ * the PASID allocated during bind() is limited by the IOMMU capacity, and by
+ * the device PASID width defined in the PCI capability or in the firmware
+ * description. Setting @max_pasid to a non-zero value smaller than this limit
+ * overrides it.
+ *
+ * The device should not be performing any DMA while this function is running,
+ * otherwise the behavior is undefined.
+ *
+ * Return 0 if initialization succeeded, or an error.
+ */
+int iommu_sva_device_init(struct device *dev, unsigned long features,
+			  unsigned int max_pasid)
+{
+	int ret;
+	struct iommu_sva_param *param;
+	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
+
+	if (!domain || !domain->ops->sva_device_init)
+		return -ENODEV;
+
+	if (features)
+		return -EINVAL;
+
+	param = kzalloc(sizeof(*param), GFP_KERNEL);
+	if (!param)
+		return -ENOMEM;
+
+	param->features		= features;
+	param->max_pasid	= max_pasid;
+
+	/*
+	 * IOMMU driver updates the limits depending on the IOMMU and device
+	 * capabilities.
+	 */
+	ret = domain->ops->sva_device_init(dev, param);
+	if (ret)
+		goto err_free_param;
+
+	mutex_lock(&dev->iommu_param->lock);
+	if (dev->iommu_param->sva_param)
+		ret = -EEXIST;
+	else
+		dev->iommu_param->sva_param = param;
+	mutex_unlock(&dev->iommu_param->lock);
+	if (ret)
+		goto err_device_shutdown;
+
+	return 0;
+
+err_device_shutdown:
+	if (domain->ops->sva_device_shutdown)
+		domain->ops->sva_device_shutdown(dev, param);
+
+err_free_param:
+	kfree(param);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iommu_sva_device_init);
+
+/**
+ * iommu_sva_device_shutdown() - Shutdown Shared Virtual Addressing for a device
+ * @dev: the device
+ *
+ * Disable SVA. Device driver should ensure that the device isn't performing any
+ * DMA while this function is running.
+ */
+int iommu_sva_device_shutdown(struct device *dev)
+{
+	struct iommu_sva_param *param;
+	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
+
+	if (!domain)
+		return -ENODEV;
+
+	mutex_lock(&dev->iommu_param->lock);
+	param = dev->iommu_param->sva_param;
+	dev->iommu_param->sva_param = NULL;
+	mutex_unlock(&dev->iommu_param->lock);
+	if (!param)
+		return -ENODEV;
+
+	if (domain->ops->sva_device_shutdown)
+		domain->ops->sva_device_shutdown(dev, param);
+
+	kfree(param);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(iommu_sva_device_shutdown);
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 0933f726d2e6..2efe7738bedb 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -212,6 +212,12 @@ struct page_response_msg {
 	u64 private_data;
 };
 
+struct iommu_sva_param {
+	unsigned long features;
+	unsigned int min_pasid;
+	unsigned int max_pasid;
+};
+
 /**
  * struct iommu_ops - iommu ops and capabilities
  * @capable: check capability
@@ -219,6 +225,8 @@ struct page_response_msg {
  * @domain_free: free iommu domain
  * @attach_dev: attach device to an iommu domain
  * @detach_dev: detach device from an iommu domain
+ * @sva_device_init: initialize Shared Virtual Adressing for a device
+ * @sva_device_shutdown: shutdown Shared Virtual Adressing for a device
  * @map: map a physically contiguous memory region to an iommu domain
  * @unmap: unmap a physically contiguous memory region from an iommu domain
  * @map_sg: map a scatter-gather list of physically contiguous memory chunks
@@ -256,6 +264,10 @@ struct iommu_ops {
 
 	int (*attach_dev)(struct iommu_domain *domain, struct device *dev);
 	void (*detach_dev)(struct iommu_domain *domain, struct device *dev);
+	int (*sva_device_init)(struct device *dev,
+			       struct iommu_sva_param *param);
+	void (*sva_device_shutdown)(struct device *dev,
+				    struct iommu_sva_param *param);
 	int (*map)(struct iommu_domain *domain, unsigned long iova,
 		   phys_addr_t paddr, size_t size, int prot);
 	size_t (*unmap)(struct iommu_domain *domain, unsigned long iova,
@@ -413,6 +425,7 @@ struct iommu_fault_param {
  * struct iommu_param - collection of per-device IOMMU data
  *
  * @fault_param: IOMMU detected device fault reporting data
+ * @sva_param: SVA parameters
  *
  * TODO: migrate other per device data pointers under iommu_dev_data, e.g.
  *	struct iommu_group	*iommu_group;
@@ -421,6 +434,7 @@ struct iommu_fault_param {
 struct iommu_param {
 	struct mutex lock;
 	struct iommu_fault_param *fault_param;
+	struct iommu_sva_param *sva_param;
 };
 
 int  iommu_device_register(struct iommu_device *iommu);
@@ -920,4 +934,22 @@ static inline int iommu_sva_invalidate(struct iommu_domain *domain,
 
 #endif /* CONFIG_IOMMU_API */
 
+#ifdef CONFIG_IOMMU_SVA
+extern int iommu_sva_device_init(struct device *dev, unsigned long features,
+				 unsigned int max_pasid);
+extern int iommu_sva_device_shutdown(struct device *dev);
+#else /* CONFIG_IOMMU_SVA */
+static inline int iommu_sva_device_init(struct device *dev,
+					unsigned long features,
+					unsigned int max_pasid)
+{
+	return -ENODEV;
+}
+
+static inline int iommu_sva_device_shutdown(struct device *dev)
+{
+	return -ENODEV;
+}
+#endif /* CONFIG_IOMMU_SVA */
+
 #endif /* __LINUX_IOMMU_H */
-- 
2.17.0