xref: /linux/drivers/misc/cxl/fault.c (revision 37744feebc086908fd89760650f458ab19071750) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright 2014 IBM Corp.
4  */
5 
6 #include <linux/workqueue.h>
7 #include <linux/sched/signal.h>
8 #include <linux/sched/mm.h>
9 #include <linux/pid.h>
10 #include <linux/mm.h>
11 #include <linux/moduleparam.h>
12 
13 #undef MODULE_PARAM_PREFIX
14 #define MODULE_PARAM_PREFIX "cxl" "."
15 #include <asm/current.h>
16 #include <asm/copro.h>
17 #include <asm/mmu.h>
18 
19 #include "cxl.h"
20 #include "trace.h"
21 
22 static bool sste_matches(struct cxl_sste *sste, struct copro_slb *slb)
23 {
24 	return ((sste->vsid_data == cpu_to_be64(slb->vsid)) &&
25 		(sste->esid_data == cpu_to_be64(slb->esid)));
26 }
27 
28 /*
29  * This finds a free SSTE for the given SLB, or returns NULL if it's already in
30  * the segment table.
31  */
32 static struct cxl_sste *find_free_sste(struct cxl_context *ctx,
33 				       struct copro_slb *slb)
34 {
35 	struct cxl_sste *primary, *sste, *ret = NULL;
36 	unsigned int mask = (ctx->sst_size >> 7) - 1; /* SSTP0[SegTableSize] */
37 	unsigned int entry;
38 	unsigned int hash;
39 
40 	if (slb->vsid & SLB_VSID_B_1T)
41 		hash = (slb->esid >> SID_SHIFT_1T) & mask;
42 	else /* 256M */
43 		hash = (slb->esid >> SID_SHIFT) & mask;
44 
45 	primary = ctx->sstp + (hash << 3);
46 
47 	for (entry = 0, sste = primary; entry < 8; entry++, sste++) {
48 		if (!ret && !(be64_to_cpu(sste->esid_data) & SLB_ESID_V))
49 			ret = sste;
50 		if (sste_matches(sste, slb))
51 			return NULL;
52 	}
53 	if (ret)
54 		return ret;
55 
56 	/* Nothing free, select an entry to cast out */
57 	ret = primary + ctx->sst_lru;
58 	ctx->sst_lru = (ctx->sst_lru + 1) & 0x7;
59 
60 	return ret;
61 }
62 
63 static void cxl_load_segment(struct cxl_context *ctx, struct copro_slb *slb)
64 {
65 	/* mask is the group index, we search primary and secondary here. */
66 	struct cxl_sste *sste;
67 	unsigned long flags;
68 
69 	spin_lock_irqsave(&ctx->sste_lock, flags);
70 	sste = find_free_sste(ctx, slb);
71 	if (!sste)
72 		goto out_unlock;
73 
74 	pr_devel("CXL Populating SST[%li]: %#llx %#llx\n",
75 			sste - ctx->sstp, slb->vsid, slb->esid);
76 	trace_cxl_ste_write(ctx, sste - ctx->sstp, slb->esid, slb->vsid);
77 
78 	sste->vsid_data = cpu_to_be64(slb->vsid);
79 	sste->esid_data = cpu_to_be64(slb->esid);
80 out_unlock:
81 	spin_unlock_irqrestore(&ctx->sste_lock, flags);
82 }
83 
84 static int cxl_fault_segment(struct cxl_context *ctx, struct mm_struct *mm,
85 			     u64 ea)
86 {
87 	struct copro_slb slb = {0,0};
88 	int rc;
89 
90 	if (!(rc = copro_calculate_slb(mm, ea, &slb))) {
91 		cxl_load_segment(ctx, &slb);
92 	}
93 
94 	return rc;
95 }
96 
97 static void cxl_ack_ae(struct cxl_context *ctx)
98 {
99 	unsigned long flags;
100 
101 	cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_AE, 0);
102 
103 	spin_lock_irqsave(&ctx->lock, flags);
104 	ctx->pending_fault = true;
105 	ctx->fault_addr = ctx->dar;
106 	ctx->fault_dsisr = ctx->dsisr;
107 	spin_unlock_irqrestore(&ctx->lock, flags);
108 
109 	wake_up_all(&ctx->wq);
110 }
111 
112 static int cxl_handle_segment_miss(struct cxl_context *ctx,
113 				   struct mm_struct *mm, u64 ea)
114 {
115 	int rc;
116 
117 	pr_devel("CXL interrupt: Segment fault pe: %i ea: %#llx\n", ctx->pe, ea);
118 	trace_cxl_ste_miss(ctx, ea);
119 
120 	if ((rc = cxl_fault_segment(ctx, mm, ea)))
121 		cxl_ack_ae(ctx);
122 	else {
123 
124 		mb(); /* Order seg table write to TFC MMIO write */
125 		cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_R, 0);
126 	}
127 
128 	return IRQ_HANDLED;
129 }
130 
131 int cxl_handle_mm_fault(struct mm_struct *mm, u64 dsisr, u64 dar)
132 {
133 	vm_fault_t flt = 0;
134 	int result;
135 	unsigned long access, flags, inv_flags = 0;
136 
137 	/*
138 	 * Add the fault handling cpu to task mm cpumask so that we
139 	 * can do a safe lockless page table walk when inserting the
140 	 * hash page table entry. This function get called with a
141 	 * valid mm for user space addresses. Hence using the if (mm)
142 	 * check is sufficient here.
143 	 */
144 	if (mm && !cpumask_test_cpu(smp_processor_id(), mm_cpumask(mm))) {
145 		cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
146 		/*
147 		 * We need to make sure we walk the table only after
148 		 * we update the cpumask. The other side of the barrier
149 		 * is explained in serialize_against_pte_lookup()
150 		 */
151 		smp_mb();
152 	}
153 	if ((result = copro_handle_mm_fault(mm, dar, dsisr, &flt))) {
154 		pr_devel("copro_handle_mm_fault failed: %#x\n", result);
155 		return result;
156 	}
157 
158 	if (!radix_enabled()) {
159 		/*
160 		 * update_mmu_cache() will not have loaded the hash since current->trap
161 		 * is not a 0x400 or 0x300, so just call hash_page_mm() here.
162 		 */
163 		access = _PAGE_PRESENT | _PAGE_READ;
164 		if (dsisr & CXL_PSL_DSISR_An_S)
165 			access |= _PAGE_WRITE;
166 
167 		if (!mm && (get_region_id(dar) != USER_REGION_ID))
168 			access |= _PAGE_PRIVILEGED;
169 
170 		if (dsisr & DSISR_NOHPTE)
171 			inv_flags |= HPTE_NOHPTE_UPDATE;
172 
173 		local_irq_save(flags);
174 		hash_page_mm(mm, dar, access, 0x300, inv_flags);
175 		local_irq_restore(flags);
176 	}
177 	return 0;
178 }
179 
180 static void cxl_handle_page_fault(struct cxl_context *ctx,
181 				  struct mm_struct *mm,
182 				  u64 dsisr, u64 dar)
183 {
184 	trace_cxl_pte_miss(ctx, dsisr, dar);
185 
186 	if (cxl_handle_mm_fault(mm, dsisr, dar)) {
187 		cxl_ack_ae(ctx);
188 	} else {
189 		pr_devel("Page fault successfully handled for pe: %i!\n", ctx->pe);
190 		cxl_ops->ack_irq(ctx, CXL_PSL_TFC_An_R, 0);
191 	}
192 }
193 
194 /*
195  * Returns the mm_struct corresponding to the context ctx.
196  * mm_users == 0, the context may be in the process of being closed.
197  */
198 static struct mm_struct *get_mem_context(struct cxl_context *ctx)
199 {
200 	if (ctx->mm == NULL)
201 		return NULL;
202 
203 	if (!atomic_inc_not_zero(&ctx->mm->mm_users))
204 		return NULL;
205 
206 	return ctx->mm;
207 }
208 
209 static bool cxl_is_segment_miss(struct cxl_context *ctx, u64 dsisr)
210 {
211 	if ((cxl_is_power8() && (dsisr & CXL_PSL_DSISR_An_DS)))
212 		return true;
213 
214 	return false;
215 }
216 
217 static bool cxl_is_page_fault(struct cxl_context *ctx, u64 dsisr)
218 {
219 	if ((cxl_is_power8()) && (dsisr & CXL_PSL_DSISR_An_DM))
220 		return true;
221 
222 	if (cxl_is_power9())
223 		return true;
224 
225 	return false;
226 }
227 
228 void cxl_handle_fault(struct work_struct *fault_work)
229 {
230 	struct cxl_context *ctx =
231 		container_of(fault_work, struct cxl_context, fault_work);
232 	u64 dsisr = ctx->dsisr;
233 	u64 dar = ctx->dar;
234 	struct mm_struct *mm = NULL;
235 
236 	if (cpu_has_feature(CPU_FTR_HVMODE)) {
237 		if (cxl_p2n_read(ctx->afu, CXL_PSL_DSISR_An) != dsisr ||
238 		    cxl_p2n_read(ctx->afu, CXL_PSL_DAR_An) != dar ||
239 		    cxl_p2n_read(ctx->afu, CXL_PSL_PEHandle_An) != ctx->pe) {
240 			/* Most likely explanation is harmless - a dedicated
241 			 * process has detached and these were cleared by the
242 			 * PSL purge, but warn about it just in case
243 			 */
244 			dev_notice(&ctx->afu->dev, "cxl_handle_fault: Translation fault regs changed\n");
245 			return;
246 		}
247 	}
248 
249 	/* Early return if the context is being / has been detached */
250 	if (ctx->status == CLOSED) {
251 		cxl_ack_ae(ctx);
252 		return;
253 	}
254 
255 	pr_devel("CXL BOTTOM HALF handling fault for afu pe: %i. "
256 		"DSISR: %#llx DAR: %#llx\n", ctx->pe, dsisr, dar);
257 
258 	if (!ctx->kernel) {
259 
260 		mm = get_mem_context(ctx);
261 		if (mm == NULL) {
262 			pr_devel("%s: unable to get mm for pe=%d pid=%i\n",
263 				 __func__, ctx->pe, pid_nr(ctx->pid));
264 			cxl_ack_ae(ctx);
265 			return;
266 		} else {
267 			pr_devel("Handling page fault for pe=%d pid=%i\n",
268 				 ctx->pe, pid_nr(ctx->pid));
269 		}
270 	}
271 
272 	if (cxl_is_segment_miss(ctx, dsisr))
273 		cxl_handle_segment_miss(ctx, mm, dar);
274 	else if (cxl_is_page_fault(ctx, dsisr))
275 		cxl_handle_page_fault(ctx, mm, dsisr, dar);
276 	else
277 		WARN(1, "cxl_handle_fault has nothing to handle\n");
278 
279 	if (mm)
280 		mmput(mm);
281 }
282 
283 static void cxl_prefault_one(struct cxl_context *ctx, u64 ea)
284 {
285 	struct mm_struct *mm;
286 
287 	mm = get_mem_context(ctx);
288 	if (mm == NULL) {
289 		pr_devel("cxl_prefault_one unable to get mm %i\n",
290 			 pid_nr(ctx->pid));
291 		return;
292 	}
293 
294 	cxl_fault_segment(ctx, mm, ea);
295 
296 	mmput(mm);
297 }
298 
299 static u64 next_segment(u64 ea, u64 vsid)
300 {
301 	if (vsid & SLB_VSID_B_1T)
302 		ea |= (1ULL << 40) - 1;
303 	else
304 		ea |= (1ULL << 28) - 1;
305 
306 	return ea + 1;
307 }
308 
309 static void cxl_prefault_vma(struct cxl_context *ctx)
310 {
311 	u64 ea, last_esid = 0;
312 	struct copro_slb slb;
313 	struct vm_area_struct *vma;
314 	int rc;
315 	struct mm_struct *mm;
316 
317 	mm = get_mem_context(ctx);
318 	if (mm == NULL) {
319 		pr_devel("cxl_prefault_vm unable to get mm %i\n",
320 			 pid_nr(ctx->pid));
321 		return;
322 	}
323 
324 	down_read(&mm->mmap_sem);
325 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
326 		for (ea = vma->vm_start; ea < vma->vm_end;
327 				ea = next_segment(ea, slb.vsid)) {
328 			rc = copro_calculate_slb(mm, ea, &slb);
329 			if (rc)
330 				continue;
331 
332 			if (last_esid == slb.esid)
333 				continue;
334 
335 			cxl_load_segment(ctx, &slb);
336 			last_esid = slb.esid;
337 		}
338 	}
339 	up_read(&mm->mmap_sem);
340 
341 	mmput(mm);
342 }
343 
344 void cxl_prefault(struct cxl_context *ctx, u64 wed)
345 {
346 	switch (ctx->afu->prefault_mode) {
347 	case CXL_PREFAULT_WED:
348 		cxl_prefault_one(ctx, wed);
349 		break;
350 	case CXL_PREFAULT_ALL:
351 		cxl_prefault_vma(ctx);
352 		break;
353 	default:
354 		break;
355 	}
356 }
357