xref: /linux/drivers/dma/idxd/submit.c (revision cdd30ebb1b9f36159d66f088b61aee264e649d7a)
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 EXPORT_SYMBOL_NS_GPL(idxd_alloc_desc, "IDXD");
65 
idxd_free_desc(struct idxd_wq * wq,struct idxd_desc * desc)66 void idxd_free_desc(struct idxd_wq *wq, struct idxd_desc *desc)
67 {
68 	int cpu = desc->cpu;
69 
70 	desc->cpu = -1;
71 	sbitmap_queue_clear(&wq->sbq, desc->id, cpu);
72 }
73 EXPORT_SYMBOL_NS_GPL(idxd_free_desc, "IDXD");
74 
list_abort_desc(struct idxd_wq * wq,struct idxd_irq_entry * ie,struct idxd_desc * desc)75 static struct idxd_desc *list_abort_desc(struct idxd_wq *wq, struct idxd_irq_entry *ie,
76 					 struct idxd_desc *desc)
77 {
78 	struct idxd_desc *d, *n;
79 
80 	lockdep_assert_held(&ie->list_lock);
81 	list_for_each_entry_safe(d, n, &ie->work_list, list) {
82 		if (d == desc) {
83 			list_del(&d->list);
84 			return d;
85 		}
86 	}
87 
88 	/*
89 	 * At this point, the desc needs to be aborted is held by the completion
90 	 * handler where it has taken it off the pending list but has not added to the
91 	 * work list. It will be cleaned up by the interrupt handler when it sees the
92 	 * IDXD_COMP_DESC_ABORT for completion status.
93 	 */
94 	return NULL;
95 }
96 
llist_abort_desc(struct idxd_wq * wq,struct idxd_irq_entry * ie,struct idxd_desc * desc)97 static void llist_abort_desc(struct idxd_wq *wq, struct idxd_irq_entry *ie,
98 			     struct idxd_desc *desc)
99 {
100 	struct idxd_desc *d, *t, *found = NULL;
101 	struct llist_node *head;
102 	LIST_HEAD(flist);
103 
104 	desc->completion->status = IDXD_COMP_DESC_ABORT;
105 	/*
106 	 * Grab the list lock so it will block the irq thread handler. This allows the
107 	 * abort code to locate the descriptor need to be aborted.
108 	 */
109 	spin_lock(&ie->list_lock);
110 	head = llist_del_all(&ie->pending_llist);
111 	if (head) {
112 		llist_for_each_entry_safe(d, t, head, llnode) {
113 			if (d == desc) {
114 				found = desc;
115 				continue;
116 			}
117 
118 			if (d->completion->status)
119 				list_add_tail(&d->list, &flist);
120 			else
121 				list_add_tail(&d->list, &ie->work_list);
122 		}
123 	}
124 
125 	if (!found)
126 		found = list_abort_desc(wq, ie, desc);
127 	spin_unlock(&ie->list_lock);
128 
129 	if (found)
130 		idxd_dma_complete_txd(found, IDXD_COMPLETE_ABORT, false,
131 				      NULL, NULL);
132 
133 	/*
134 	 * completing the descriptor will return desc to allocator and
135 	 * the desc can be acquired by a different process and the
136 	 * desc->list can be modified.  Delete desc from list so the
137 	 * list traversing does not get corrupted by the other process.
138 	 */
139 	list_for_each_entry_safe(d, t, &flist, list) {
140 		list_del_init(&d->list);
141 		idxd_dma_complete_txd(found, IDXD_COMPLETE_ABORT, true,
142 				      NULL, NULL);
143 	}
144 }
145 
146 /*
147  * ENQCMDS typically fail when the WQ is inactive or busy. On host submission, the driver
148  * has better control of number of descriptors being submitted to a shared wq by limiting
149  * the number of driver allocated descriptors to the wq size. However, when the swq is
150  * exported to a guest kernel, it may be shared with multiple guest kernels. This means
151  * the likelihood of getting busy returned on the swq when submitting goes significantly up.
152  * Having a tunable retry mechanism allows the driver to keep trying for a bit before giving
153  * up. The sysfs knob can be tuned by the system administrator.
154  */
idxd_enqcmds(struct idxd_wq * wq,void __iomem * portal,const void * desc)155 int idxd_enqcmds(struct idxd_wq *wq, void __iomem *portal, const void *desc)
156 {
157 	unsigned int retries = wq->enqcmds_retries;
158 	int rc;
159 
160 	do {
161 		rc = enqcmds(portal, desc);
162 		if (rc == 0)
163 			break;
164 		cpu_relax();
165 	} while (retries--);
166 
167 	return rc;
168 }
169 
idxd_submit_desc(struct idxd_wq * wq,struct idxd_desc * desc)170 int idxd_submit_desc(struct idxd_wq *wq, struct idxd_desc *desc)
171 {
172 	struct idxd_device *idxd = wq->idxd;
173 	struct idxd_irq_entry *ie = NULL;
174 	u32 desc_flags = desc->hw->flags;
175 	void __iomem *portal;
176 	int rc;
177 
178 	if (idxd->state != IDXD_DEV_ENABLED)
179 		return -EIO;
180 
181 	if (!percpu_ref_tryget_live(&wq->wq_active)) {
182 		wait_for_completion(&wq->wq_resurrect);
183 		if (!percpu_ref_tryget_live(&wq->wq_active))
184 			return -ENXIO;
185 	}
186 
187 	portal = idxd_wq_portal_addr(wq);
188 
189 	/*
190 	 * Pending the descriptor to the lockless list for the irq_entry
191 	 * that we designated the descriptor to.
192 	 */
193 	if (desc_flags & IDXD_OP_FLAG_RCI) {
194 		ie = &wq->ie;
195 		desc->hw->int_handle = ie->int_handle;
196 		llist_add(&desc->llnode, &ie->pending_llist);
197 	}
198 
199 	/*
200 	 * The wmb() flushes writes to coherent DMA data before
201 	 * possibly triggering a DMA read. The wmb() is necessary
202 	 * even on UP because the recipient is a device.
203 	 */
204 	wmb();
205 
206 	if (wq_dedicated(wq)) {
207 		iosubmit_cmds512(portal, desc->hw, 1);
208 	} else {
209 		rc = idxd_enqcmds(wq, portal, desc->hw);
210 		if (rc < 0) {
211 			percpu_ref_put(&wq->wq_active);
212 			/* abort operation frees the descriptor */
213 			if (ie)
214 				llist_abort_desc(wq, ie, desc);
215 			return rc;
216 		}
217 	}
218 
219 	percpu_ref_put(&wq->wq_active);
220 	return 0;
221 }
222 EXPORT_SYMBOL_NS_GPL(idxd_submit_desc, "IDXD");
223