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
10static DEFINE_MUTEX(iommu_sva_lock);
11static 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 */
26int 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}
51EXPORT_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 */
59void 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}
66EXPORT_SYMBOL_GPL(iommu_sva_free_pasid);
67
68/* ioasid_find getter() requires a void * argument */
69static 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 */
82struct mm_struct *iommu_sva_find(ioasid_t pasid)
83{
84	return ioasid_find(&iommu_sva_pasid, pasid, __mmget_not_zero);
85}
86EXPORT_SYMBOL_GPL(iommu_sva_find);