/*
   * Copyright © 2015 Intel Corporation.
   *
   * Authors: David Woodhouse <David.Woodhouse@intel.com>
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms and conditions of the GNU General Public License,
   * version 2, as published by the Free Software Foundation.
   *
   * This program is distributed in the hope it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
   * more details.
   */
  
  #ifndef __INTEL_SVM_H__
  #define __INTEL_SVM_H__

  struct device;

  struct svm_dev_ops {
  	void (*fault_cb)(struct device *dev, int pasid, u64 address,
  			 u32 private, int rwxp, int response);
  };
  
  /* Values for rxwp in fault_cb callback */
  #define SVM_REQ_READ	(1<<3)
  #define SVM_REQ_WRITE	(1<<2)
  #define SVM_REQ_EXEC	(1<<1)
  #define SVM_REQ_PRIV	(1<<0)

  
  /*
   * The SVM_FLAG_PRIVATE_PASID flag requests a PASID which is *not* the "main"
   * PASID for the current process. Even if a PASID already exists, a new one
   * will be allocated. And the PASID allocated with SVM_FLAG_PRIVATE_PASID
   * will not be given to subsequent callers. This facility allows a driver to
   * disambiguate between multiple device contexts which access the same MM,
   * if there is no other way to do so. It should be used sparingly, if at all.
   */

  #define SVM_FLAG_PRIVATE_PASID		(1<<0)
  
  /*
   * The SVM_FLAG_SUPERVISOR_MODE flag requests a PASID which can be used only
   * for access to kernel addresses. No IOTLB flushes are automatically done
   * for kernel mappings; it is valid only for access to the kernel's static
   * 1:1 mapping of physical memory — not to vmalloc or even module mappings.
   * A future API addition may permit the use of such ranges, by means of an
   * explicit IOTLB flush call (akin to the DMA API's unmap method).
   *
   * It is unlikely that we will ever hook into flush_tlb_kernel_range() to
   * do such IOTLB flushes automatically.
   */
  #define SVM_FLAG_SUPERVISOR_MODE	(1<<1)

  #ifdef CONFIG_INTEL_IOMMU_SVM

  /**
   * intel_svm_bind_mm() - Bind the current process to a PASID
   * @dev:	Device to be granted acccess
   * @pasid:	Address for allocated PASID

   * @flags:	Flags. Later for requesting supervisor mode, etc.
   * @ops:	Callbacks to device driver

   *
   * This function attempts to enable PASID support for the given device.
   * If the @pasid argument is non-%NULL, a PASID is allocated for access
   * to the MM of the current process.
   *
   * By using a %NULL value for the @pasid argument, this function can
   * be used to simply validate that PASID support is available for the
   * given device — i.e. that it is behind an IOMMU which has the
   * requisite support, and is enabled.
   *
   * Page faults are handled transparently by the IOMMU code, and there
   * should be no need for the device driver to be involved. If a page
   * fault cannot be handled (i.e. is an invalid address rather than
   * just needs paging in), then the page request will be completed by
   * the core IOMMU code with appropriate status, and the device itself
   * can then report the resulting fault to its driver via whatever
   * mechanism is appropriate.
   *
   * Multiple calls from the same process may result in the same PASID
   * being re-used. A reference count is kept.
   */

  extern int intel_svm_bind_mm(struct device *dev, int *pasid, int flags,
  			     struct svm_dev_ops *ops);

  
  /**
   * intel_svm_unbind_mm() - Unbind a specified PASID
   * @dev:	Device for which PASID was allocated
   * @pasid:	PASID value to be unbound
   *
   * This function allows a PASID to be retired when the device no
   * longer requires access to the address space of a given process.
   *
   * If the use count for the PASID in question reaches zero, the
   * PASID is revoked and may no longer be used by hardware.
   *
   * Device drivers are required to ensure that no access (including
   * page requests) is currently outstanding for the PASID in question,
   * before calling this function.
   */
  extern int intel_svm_unbind_mm(struct device *dev, int pasid);

  /**
   * intel_svm_is_pasid_valid() - check if pasid is valid
   * @dev:	Device for which PASID was allocated
   * @pasid:	PASID value to be checked
   *
   * This function checks if the specified pasid is still valid. A
   * valid pasid means the backing mm is still having a valid user.
   * For kernel callers init_mm is always valid. for other mm, if mm->mm_users
   * is non-zero, it is valid.
   *
   * returns -EINVAL if invalid pasid, 0 if pasid ref count is invalid
   * 1 if pasid is valid.
   */
  extern int intel_svm_is_pasid_valid(struct device *dev, int pasid);

  #else /* CONFIG_INTEL_IOMMU_SVM */

  static inline int intel_svm_bind_mm(struct device *dev, int *pasid,
  				    int flags, struct svm_dev_ops *ops)

  {
  	return -ENOSYS;
  }
  
  static inline int intel_svm_unbind_mm(struct device *dev, int pasid)
  {
  	BUG();
  }

  
  static int intel_svm_is_pasid_valid(struct device *dev, int pasid)
  {
  	return -EINVAL;
  }

  #endif /* CONFIG_INTEL_IOMMU_SVM */

  #define intel_svm_available(dev) (!intel_svm_bind_mm((dev), NULL, 0, NULL))

  
  #endif /* __INTEL_SVM_H__ */