1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright(c) 2019 Intel Corporation. All rights rsvd. */
3 #include <linux/init.h>
4 #include <linux/kernel.h>
5 #include <linux/module.h>
6 #include <linux/pci.h>
7 #include <uapi/linux/idxd.h>
8 #include "idxd.h"
9 #include "registers.h"
10 
__get_desc(struct idxd_wq * wq,int idx,int cpu)11 static struct idxd_desc *__get_desc(struct idxd_wq *wq, int idx, int cpu)
12 {
13 	struct idxd_desc *desc;
14 	struct idxd_device *idxd = wq->idxd;
15 
16 	desc = wq->descs[idx];
17 	memset(desc->hw, 0, sizeof(struct dsa_hw_desc));
18 	memset(desc->completion, 0, idxd->data->compl_size);
19 	desc->cpu = cpu;
20 
21 	if (device_pasid_enabled(idxd))
22 		desc->hw->pasid = idxd->pasid;
23 
24 	return desc;
25 }
26 
idxd_alloc_desc(struct idxd_wq * wq,enum idxd_op_type optype)27 struct idxd_desc *idxd_alloc_desc(struct idxd_wq *wq, enum idxd_op_type optype)
28 {
29 	int cpu, idx;
30 	struct idxd_device *idxd = wq->idxd;
31 	DEFINE_SBQ_WAIT(wait);
32 	struct sbq_wait_state *ws;
33 	struct sbitmap_queue *sbq;
34 
35 	if (idxd->state != IDXD_DEV_ENABLED)
36 		return ERR_PTR(-EIO);
37 
38 	sbq = &wq->sbq;
39 	idx = sbitmap_queue_get(sbq, &cpu);
40 	if (idx < 0) {
41 		if (optype == IDXD_OP_NONBLOCK)
42 			return ERR_PTR(-EAGAIN);
43 	} else {
44 		return __get_desc(wq, idx, cpu);
45 	}
46 
47 	ws = &sbq->ws[0];
48 	for (;;) {
49 		sbitmap_prepare_to_wait(sbq, ws, &wait, TASK_INTERRUPTIBLE);
50 		if (signal_pending_state(TASK_INTERRUPTIBLE, current))
51 			break;
52 		idx = sbitmap_queue_get(sbq, &cpu);
53 		if (idx >= 0)
54 			break;
55 		schedule();
56 	}
57 
58 	sbitmap_finish_wait(sbq, ws, &wait);
59 	if (idx < 0)
60 		return ERR_PTR(-EAGAIN);
61 
62 	return __get_desc(wq, idx, cpu);
63 }
64 
idxd_free_desc(struct idxd_wq * wq,struct idxd_desc * desc)65 void idxd_free_desc(struct idxd_wq *wq, struct idxd_desc *desc)
66 {
67 	int cpu = desc->cpu;
68 
69 	desc->cpu = -1;
70 	sbitmap_queue_clear(&wq->sbq, desc->id, cpu);
71 }
72 
list_abort_desc(struct idxd_wq * wq,struct idxd_irq_entry * ie,struct idxd_desc * desc)73 static struct idxd_desc *list_abort_desc(struct idxd_wq *wq, struct idxd_irq_entry *ie,
74 					 struct idxd_desc *desc)
75 {
76 	struct idxd_desc *d, *n;
77 
78 	lockdep_assert_held(&ie->list_lock);
79 	list_for_each_entry_safe(d, n, &ie->work_list, list) {
80 		if (d == desc) {
81 			list_del(&d->list);
82 			return d;
83 		}
84 	}
85 
86 	/*
87 	 * At this point, the desc needs to be aborted is held by the completion
88 	 * handler where it has taken it off the pending list but has not added to the
89 	 * work list. It will be cleaned up by the interrupt handler when it sees the
90 	 * IDXD_COMP_DESC_ABORT for completion status.
91 	 */
92 	return NULL;
93 }
94 
llist_abort_desc(struct idxd_wq * wq,struct idxd_irq_entry * ie,struct idxd_desc * desc)95 static void llist_abort_desc(struct idxd_wq *wq, struct idxd_irq_entry *ie,
96 			     struct idxd_desc *desc)
97 {
98 	struct idxd_desc *d, *t, *found = NULL;
99 	struct llist_node *head;
100 	LIST_HEAD(flist);
101 
102 	desc->completion->status = IDXD_COMP_DESC_ABORT;
103 	/*
104 	 * Grab the list lock so it will block the irq thread handler. This allows the
105 	 * abort code to locate the descriptor need to be aborted.
106 	 */
107 	spin_lock(&ie->list_lock);
108 	head = llist_del_all(&ie->pending_llist);
109 	if (head) {
110 		llist_for_each_entry_safe(d, t, head, llnode) {
111 			if (d == desc) {
112 				found = desc;
113 				continue;
114 			}
115 
116 			if (d->completion->status)
117 				list_add_tail(&d->list, &flist);
118 			else
119 				list_add_tail(&d->list, &ie->work_list);
120 		}
121 	}
122 
123 	if (!found)
124 		found = list_abort_desc(wq, ie, desc);
125 	spin_unlock(&ie->list_lock);
126 
127 	if (found)
128 		idxd_dma_complete_txd(found, IDXD_COMPLETE_ABORT, false);
129 
130 	/*
131 	 * completing the descriptor will return desc to allocator and
132 	 * the desc can be acquired by a different process and the
133 	 * desc->list can be modified.  Delete desc from list so the
134 	 * list trasversing does not get corrupted by the other process.
135 	 */
136 	list_for_each_entry_safe(d, t, &flist, list) {
137 		list_del_init(&d->list);
138 		idxd_dma_complete_txd(found, IDXD_COMPLETE_ABORT, true);
139 	}
140 }
141 
142 /*
143  * ENQCMDS typically fail when the WQ is inactive or busy. On host submission, the driver
144  * has better control of number of descriptors being submitted to a shared wq by limiting
145  * the number of driver allocated descriptors to the wq size. However, when the swq is
146  * exported to a guest kernel, it may be shared with multiple guest kernels. This means
147  * the likelihood of getting busy returned on the swq when submitting goes significantly up.
148  * Having a tunable retry mechanism allows the driver to keep trying for a bit before giving
149  * up. The sysfs knob can be tuned by the system administrator.
150  */
idxd_enqcmds(struct idxd_wq * wq,void __iomem * portal,const void * desc)151 int idxd_enqcmds(struct idxd_wq *wq, void __iomem *portal, const void *desc)
152 {
153 	unsigned int retries = wq->enqcmds_retries;
154 	int rc;
155 
156 	do {
157 		rc = enqcmds(portal, desc);
158 		if (rc == 0)
159 			break;
160 		cpu_relax();
161 	} while (retries--);
162 
163 	return rc;
164 }
165 
idxd_submit_desc(struct idxd_wq * wq,struct idxd_desc * desc)166 int idxd_submit_desc(struct idxd_wq *wq, struct idxd_desc *desc)
167 {
168 	struct idxd_device *idxd = wq->idxd;
169 	struct idxd_irq_entry *ie = NULL;
170 	u32 desc_flags = desc->hw->flags;
171 	void __iomem *portal;
172 	int rc;
173 
174 	if (idxd->state != IDXD_DEV_ENABLED)
175 		return -EIO;
176 
177 	if (!percpu_ref_tryget_live(&wq->wq_active)) {
178 		wait_for_completion(&wq->wq_resurrect);
179 		if (!percpu_ref_tryget_live(&wq->wq_active))
180 			return -ENXIO;
181 	}
182 
183 	portal = idxd_wq_portal_addr(wq);
184 
185 	/*
186 	 * The wmb() flushes writes to coherent DMA data before
187 	 * possibly triggering a DMA read. The wmb() is necessary
188 	 * even on UP because the recipient is a device.
189 	 */
190 	wmb();
191 
192 	/*
193 	 * Pending the descriptor to the lockless list for the irq_entry
194 	 * that we designated the descriptor to.
195 	 */
196 	if (desc_flags & IDXD_OP_FLAG_RCI) {
197 		ie = &wq->ie;
198 		desc->hw->int_handle = ie->int_handle;
199 		llist_add(&desc->llnode, &ie->pending_llist);
200 	}
201 
202 	if (wq_dedicated(wq)) {
203 		iosubmit_cmds512(portal, desc->hw, 1);
204 	} else {
205 		rc = idxd_enqcmds(wq, portal, desc->hw);
206 		if (rc < 0) {
207 			percpu_ref_put(&wq->wq_active);
208 			/* abort operation frees the descriptor */
209 			if (ie)
210 				llist_abort_desc(wq, ie, desc);
211 			return rc;
212 		}
213 	}
214 
215 	percpu_ref_put(&wq->wq_active);
216 	return 0;
217 }
218