drivers/iommu/iommu-sva-lib.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Helpers for IOMMU drivers implementing SVA
   4  */
   5 #include <linux/mutex.h>
   6 #include <linux/sched/mm.h>
   7
   8 #include "iommu-sva-lib.h"
   9
  10 static DEFINE_MUTEX(iommu_sva_lock);
  11 static DECLARE_IOASID_SET(iommu_sva_pasid);
  12
  13 /**
  14  * iommu_sva_alloc_pasid - Allocate a PASID for the mm
  15  * @mm: the mm
  16  * @min: minimum PASID value (inclusive)
  17  * @max: maximum PASID value (inclusive)
  18  *
  19  * Try to allocate a PASID for this mm, or take a reference to the existing one
  20  * provided it fits within the [@min, @max] range. On success the PASID is
  21  * available in mm->pasid, and must be released with iommu_sva_free_pasid().
  22  * @min must be greater than 0, because 0 indicates an unused mm->pasid.
  23  *
  24  * Returns 0 on success and < 0 on error.
  25  */
  26 int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
  27 {
  28         int ret = 0;
  29         ioasid_t pasid;
  30
  31         if (min == INVALID_IOASID || max == INVALID_IOASID ||
  32             min == 0 || max < min)
  33                 return -EINVAL;
  34
  35         mutex_lock(&iommu_sva_lock);
  36         if (mm->pasid) {
  37                 if (mm->pasid >= min && mm->pasid <= max)
  38                         ioasid_get(mm->pasid);
  39                 else
  40                         ret = -EOVERFLOW;
  41         } else {
  42                 pasid = ioasid_alloc(&iommu_sva_pasid, min, max, mm);
  43                 if (pasid == INVALID_IOASID)
  44                         ret = -ENOMEM;
  45                 else
  46                         mm->pasid = pasid;
  47         }
  48         mutex_unlock(&iommu_sva_lock);
  49         return ret;
  50 }
  51 EXPORT_SYMBOL_GPL(iommu_sva_alloc_pasid);
  52
  53 /**
  54  * iommu_sva_free_pasid - Release the mm's PASID
  55  * @mm: the mm
  56  *
  57  * Drop one reference to a PASID allocated with iommu_sva_alloc_pasid()
  58  */
  59 void iommu_sva_free_pasid(struct mm_struct *mm)
  60 {
  61         mutex_lock(&iommu_sva_lock);
  62         if (ioasid_put(mm->pasid))
  63                 mm->pasid = 0;
  64         mutex_unlock(&iommu_sva_lock);
  65 }
  66 EXPORT_SYMBOL_GPL(iommu_sva_free_pasid);
  67
  68 /* ioasid_find getter() requires a void * argument */
  69 static bool __mmget_not_zero(void *mm)
  70 {
  71         return mmget_not_zero(mm);
  72 }
  73
  74 /**
  75  * iommu_sva_find() - Find mm associated to the given PASID
  76  * @pasid: Process Address Space ID assigned to the mm
  77  *
  78  * On success a reference to the mm is taken, and must be released with mmput().
  79  *
  80  * Returns the mm corresponding to this PASID, or an error if not found.
  81  */
  82 struct mm_struct *iommu_sva_find(ioasid_t pasid)
  83 {
  84         return ioasid_find(&iommu_sva_pasid, pasid, __mmget_not_zero);
  85 }
  86 EXPORT_SYMBOL_GPL(iommu_sva_find);