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![Alexey Kardashevskiy](/assets/img/avatar_default.png)
VFIO is designed to be used via ioctls on file descriptors returned by VFIO. However in some situations support for an external user is required. The first user is KVM on PPC64 (SPAPR TCE protocol) which is going to use the existing VFIO groups for exclusive access in real/virtual mode on a host to avoid passing map/unmap requests to the user space which would made things pretty slow. The protocol includes: 1. do normal VFIO init operation: - opening a new container; - attaching group(s) to it; - setting an IOMMU driver for a container. When IOMMU is set for a container, all groups in it are considered ready to use by an external user. 2. User space passes a group fd to an external user. The external user calls vfio_group_get_external_user() to verify that: - the group is initialized; - IOMMU is set for it. If both checks passed, vfio_group_get_external_user() increments the container user counter to prevent the VFIO group from disposal before KVM exits. 3. The external user calls vfio_external_user_iommu_id() to know an IOMMU ID. PPC64 KVM uses it to link logical bus number (LIOBN) with IOMMU ID. 4. When the external KVM finishes, it calls vfio_group_put_external_user() to release the VFIO group. This call decrements the container user counter. Everything gets released. The "vfio: Limit group opens" patch is also required for the consistency. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
100 lines
3.2 KiB
C
100 lines
3.2 KiB
C
/*
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* VFIO API definition
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*
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* Copyright (C) 2012 Red Hat, Inc. All rights reserved.
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* Author: Alex Williamson <alex.williamson@redhat.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef VFIO_H
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#define VFIO_H
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#include <linux/iommu.h>
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#include <linux/mm.h>
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#include <uapi/linux/vfio.h>
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/**
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* struct vfio_device_ops - VFIO bus driver device callbacks
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*
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* @open: Called when userspace creates new file descriptor for device
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* @release: Called when userspace releases file descriptor for device
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* @read: Perform read(2) on device file descriptor
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* @write: Perform write(2) on device file descriptor
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* @ioctl: Perform ioctl(2) on device file descriptor, supporting VFIO_DEVICE_*
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* operations documented below
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* @mmap: Perform mmap(2) on a region of the device file descriptor
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*/
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struct vfio_device_ops {
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char *name;
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int (*open)(void *device_data);
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void (*release)(void *device_data);
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ssize_t (*read)(void *device_data, char __user *buf,
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size_t count, loff_t *ppos);
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ssize_t (*write)(void *device_data, const char __user *buf,
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size_t count, loff_t *size);
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long (*ioctl)(void *device_data, unsigned int cmd,
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unsigned long arg);
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int (*mmap)(void *device_data, struct vm_area_struct *vma);
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};
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extern int vfio_add_group_dev(struct device *dev,
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const struct vfio_device_ops *ops,
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void *device_data);
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extern void *vfio_del_group_dev(struct device *dev);
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extern struct vfio_device *vfio_device_get_from_dev(struct device *dev);
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extern void vfio_device_put(struct vfio_device *device);
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extern void *vfio_device_data(struct vfio_device *device);
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/**
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* struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks
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*/
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struct vfio_iommu_driver_ops {
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char *name;
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struct module *owner;
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void *(*open)(unsigned long arg);
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void (*release)(void *iommu_data);
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ssize_t (*read)(void *iommu_data, char __user *buf,
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size_t count, loff_t *ppos);
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ssize_t (*write)(void *iommu_data, const char __user *buf,
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size_t count, loff_t *size);
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long (*ioctl)(void *iommu_data, unsigned int cmd,
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unsigned long arg);
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int (*mmap)(void *iommu_data, struct vm_area_struct *vma);
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int (*attach_group)(void *iommu_data,
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struct iommu_group *group);
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void (*detach_group)(void *iommu_data,
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struct iommu_group *group);
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};
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extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
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extern void vfio_unregister_iommu_driver(
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const struct vfio_iommu_driver_ops *ops);
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/**
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* offsetofend(TYPE, MEMBER)
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*
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* @TYPE: The type of the structure
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* @MEMBER: The member within the structure to get the end offset of
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*
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* Simple helper macro for dealing with variable sized structures passed
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* from user space. This allows us to easily determine if the provided
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* structure is sized to include various fields.
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*/
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#define offsetofend(TYPE, MEMBER) ({ \
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TYPE tmp; \
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offsetof(TYPE, MEMBER) + sizeof(tmp.MEMBER); }) \
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/*
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* External user API
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*/
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extern struct vfio_group *vfio_group_get_external_user(struct file *filep);
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extern void vfio_group_put_external_user(struct vfio_group *group);
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extern int vfio_external_user_iommu_id(struct vfio_group *group);
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#endif /* VFIO_H */
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