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

Auger Eric
2018-09-05T11:29:10Z

Hi Jean-Philippe,
On 05/11/2018 09:06 PM, Jean-Philippe Brucker wrote:
> 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)
what about min_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;
So you are likely to call sva_device_init even if it was already called
(ie. dev->iommu_param->sva_param is already set). Can't you test whether
dev->iommu_param->sva_param is already set first?
> +
> + 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)
Not sure the returned value is required for a shutdown operation.
> +{
> + 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 {
What are the feature values?
> + 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
Addressing
> + * @sva_device_shutdown: shutdown Shared Virtual Adressing for a device
Addressing
> * @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 */
>

Thanks

Eric