> From: Jean-Philippe Brucker
> Sent: Tuesday, February 13, 2018 2:33 AM
>
> Shared Virtual Addressing (SVA) provides a way for device drivers to bind
> process address spaces to devices. This requires the IOMMU to support the
> same page table format as CPUs, and requires the system to support I/O
"same" is a bit restrictive. "compatible" is better as you used in coverletter.
:-)
> 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.
>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.bruc...@arm.com>
> ---
> drivers/iommu/Kconfig | 10 ++++++
> drivers/iommu/Makefile | 1 +
> drivers/iommu/iommu-sva.c | 90
> +++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/iommu.h | 32 +++++++++++++++++
> 4 files changed, 133 insertions(+)
> create mode 100644 drivers/iommu/iommu-sva.c
>
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index f3a21343e636..555147a61f7c 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -74,6 +74,16 @@ config IOMMU_DMA
> select IOMMU_IOVA
> select NEED_SG_DMA_LENGTH
>
> +config IOMMU_SVA
> + bool "Shared Virtual Addressing API for the IOMMU"
> + select IOMMU_API
> + help
> + Enable process address space management for the IOMMU API. In
> systems
> + that support it, device drivers can bind process address spaces to
> + devices and share their page tables using this API.
"their page table" is a bit confusing here.
> +
> + If unsure, say N here.
> +
> 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..cab5d723520f
> --- /dev/null
> +++ b/drivers/iommu/iommu-sva.c
> @@ -0,0 +1,90 @@
> +/*
> + * Track processes address spaces bound to devices and allocate PASIDs.
> + *
> + * Copyright (C) 2018 ARM Ltd.
> + * Author: Jean-Philippe Brucker <jean-philippe.bruc...@arm.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0
> + */
> +
> +#include <linux/iommu.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.
> + *
> + * - If the device should support multiple address spaces (e.g. PCI PASID),
> + * IOMMU_SVA_FEAT_PASID must be requested.
I think it is by default assumed when using this API, based on definition of
SVA. Can you elaborate the situation where this flag can be cleared?
> + *
> + * 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.
> + *
> + * - If the device should support I/O Page Faults (e.g. PCI PRI),
> + * IOMMU_SVA_FEAT_IOPF must be requested.
> + *
> + * The device should not be be performing any DMA while this function is
remove double "be"
> + * 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;
> + unsigned int min_pasid = 0;
> + struct iommu_param *dev_param = dev->iommu_param;
> + struct iommu_domain *domain =
> iommu_get_domain_for_dev(dev);
> +
> + if (!domain || !dev_param || !domain->ops->sva_device_init)
> + return -ENODEV;
> +
> + /*
> + * IOMMU driver updates the limits depending on the IOMMU and
> device
> + * capabilities.
> + */
> + ret = domain->ops->sva_device_init(dev, features, &min_pasid,
> + &max_pasid);
> + if (ret)
> + return ret;
> +
> + /* FIXME: racy. Next version should have a mutex (same as fault
> handler) */
> + dev_param->sva_features = features;
> + dev_param->min_pasid = min_pasid;
> + dev_param->max_pasid = max_pasid;
what's the point of min_pasid here?
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_device_init);
> +
> +/**
> + * iommu_sva_device_shutdown() - Shutdown Shared Virtual Addressing
> for a device
> + * @dev: the device
> + *
> + * Disable SVA. The device should not be performing any DMA while this
> function
> + * is running.
> + */
> +int iommu_sva_device_shutdown(struct device *dev)
> +{
> + struct iommu_param *dev_param = dev->iommu_param;
> + struct iommu_domain *domain =
> iommu_get_domain_for_dev(dev);
> +
> + if (!domain)
> + return -ENODEV;
> +
> + if (domain->ops->sva_device_shutdown)
> + domain->ops->sva_device_shutdown(dev);
> +
> + dev_param->sva_features = 0;
> + dev_param->min_pasid = 0;
> + dev_param->max_pasid = 0;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_device_shutdown);
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 66ef406396e9..e9e09eecdece 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -60,6 +60,11 @@ typedef int (*iommu_fault_handler_t)(struct
> iommu_domain *,
> struct device *, unsigned long, int, void *);
> typedef int (*iommu_dev_fault_handler_t)(struct iommu_fault_event *,
> void *);
>
> +/* Request PASID support */
> +#define IOMMU_SVA_FEAT_PASID (1 << 0)
> +/* Request I/O page fault support */
> +#define IOMMU_SVA_FEAT_IOPF (1 << 1)
> +
> struct iommu_domain_geometry {
> dma_addr_t aperture_start; /* First address that can be mapped
> */
> dma_addr_t aperture_end; /* Last address that can be mapped
> */
> @@ -197,6 +202,8 @@ 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
> @@ -230,6 +237,10 @@ 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, unsigned long features,
> + unsigned int *min_pasid,
> + unsigned int *max_pasid);
> + void (*sva_device_shutdown)(struct device *dev);
> 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,
> @@ -385,6 +396,9 @@ struct iommu_fault_param {
> */
> struct iommu_param {
> struct iommu_fault_param *fault_param;
> + unsigned long sva_features;
> + unsigned int min_pasid;
> + unsigned int max_pasid;
> };
>
> int iommu_device_register(struct iommu_device *iommu);
> @@ -878,4 +892,22 @@ const struct iommu_ops
> *iommu_ops_from_fwnode(struct fwnode_handle *fwnode)
>
> #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 */
> --
> 2.15.1
>
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