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2023-12-11 072de836f53be56a70cecf70b43ae43b7ce17376 
 kernel/arch/arm64/mm/context.c
....@@ -1,22 +1,12 @@
1
+// SPDX-License-Identifier: GPL-2.0-only
12 /*
23  * Based on arch/arm/mm/context.c
34  *
45  * Copyright (C) 2002-2003 Deep Blue Solutions Ltd, all rights reserved.
56  * Copyright (C) 2012 ARM Ltd.
6
- *
7
- * This program is free software; you can redistribute it and/or modify
8
- * it under the terms of the GNU General Public License version 2 as
9
- * published by the Free Software Foundation.
10
- *
11
- * This program is distributed in the hope that it will be useful,
12
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
13
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14
- * GNU General Public License for more details.
15
- *
16
- * You should have received a copy of the GNU General Public License
17
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
187  */
198 
9
+#include <linux/bitfield.h>
2010 #include <linux/bitops.h>
2111 #include <linux/sched.h>
2212 #include <linux/slab.h>
....@@ -37,18 +27,16 @@
3727 static DEFINE_PER_CPU(u64, reserved_asids);
3828 static cpumask_t tlb_flush_pending;
3929 
30
+static unsigned long max_pinned_asids;
31
+static unsigned long nr_pinned_asids;
32
+static unsigned long *pinned_asid_map;
33
+
4034 #define ASID_MASK		(~GENMASK(asid_bits - 1, 0))
4135 #define ASID_FIRST_VERSION	(1UL << asid_bits)
4236 
43
-#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
44
-#define NUM_USER_ASIDS		(ASID_FIRST_VERSION >> 1)
45
-#define asid2idx(asid)		(((asid) & ~ASID_MASK) >> 1)
46
-#define idx2asid(idx)		(((idx) << 1) & ~ASID_MASK)
47
-#else
48
-#define NUM_USER_ASIDS		(ASID_FIRST_VERSION)
37
+#define NUM_USER_ASIDS		ASID_FIRST_VERSION
4938 #define asid2idx(asid)		((asid) & ~ASID_MASK)
5039 #define idx2asid(idx)		asid2idx(idx)
51
-#endif
5240 
5341 /* Get the ASIDBits supported by the current CPU */
5442 static u32 get_cpu_asid_bits(void)
....@@ -61,7 +49,7 @@
6149 	default:
6250 		pr_warn("CPU%d: Unknown ASID size (%d); assuming 8-bit\n",
6351 					smp_processor_id(),  fld);
64
-		/* Fallthrough */
52
+		fallthrough;
6553 	case 0:
6654 		asid = 8;
6755 		break;
....@@ -88,13 +76,38 @@
8876 	}
8977 }
9078 
91
-static void flush_context(unsigned int cpu)
79
+static void set_kpti_asid_bits(unsigned long *map)
80
+{
81
+	unsigned int len = BITS_TO_LONGS(NUM_USER_ASIDS) * sizeof(unsigned long);
82
+	/*
83
+	 * In case of KPTI kernel/user ASIDs are allocated in
84
+	 * pairs, the bottom bit distinguishes the two: if it
85
+	 * is set, then the ASID will map only userspace. Thus
86
+	 * mark even as reserved for kernel.
87
+	 */
88
+	memset(map, 0xaa, len);
89
+}
90
+
91
+static void set_reserved_asid_bits(void)
92
+{
93
+	if (pinned_asid_map)
94
+		bitmap_copy(asid_map, pinned_asid_map, NUM_USER_ASIDS);
95
+	else if (arm64_kernel_unmapped_at_el0())
96
+		set_kpti_asid_bits(asid_map);
97
+	else
98
+		bitmap_clear(asid_map, 0, NUM_USER_ASIDS);
99
+}
100
+
101
+#define asid_gen_match(asid) \
102
+	(!(((asid) ^ atomic64_read(&asid_generation)) >> asid_bits))
103
+
104
+static void flush_context(void)
92105 {
93106 	int i;
94107 	u64 asid;
95108 
96109 	/* Update the list of reserved ASIDs and the ASID bitmap. */
97
-	bitmap_clear(asid_map, 0, NUM_USER_ASIDS);
110
+	set_reserved_asid_bits();
98111 
99112 	for_each_possible_cpu(i) {
100113 		asid = atomic64_xchg_relaxed(&per_cpu(active_asids, i), 0);
....@@ -142,7 +155,7 @@
142155 	return hit;
143156 }
144157 
145
-static u64 new_context(struct mm_struct *mm, unsigned int cpu)
158
+static u64 new_context(struct mm_struct *mm)
146159 {
147160 	static u32 cur_idx = 1;
148161 	u64 asid = atomic64_read(&mm->context.id);
....@@ -156,6 +169,14 @@
156169 		 * can continue to use it and this was just a false alarm.
157170 		 */
158171 		if (check_update_reserved_asid(asid, newasid))
172
+			return newasid;
173
+
174
+		/*
175
+		 * If it is pinned, we can keep using it. Note that reserved
176
+		 * takes priority, because even if it is also pinned, we need to
177
+		 * update the generation into the reserved_asids.
178
+		 */
179
+		if (refcount_read(&mm->context.pinned))
159180 			return newasid;
160181 
161182 		/*
....@@ -180,7 +201,7 @@
180201 	/* We're out of ASIDs, so increment the global generation count */
181202 	generation = atomic64_add_return_relaxed(ASID_FIRST_VERSION,
182203 						 &asid_generation);
183
-	flush_context(cpu);
204
+	flush_context();
184205 
185206 	/* We have more ASIDs than CPUs, so this will always succeed */
186207 	asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1);
....@@ -191,10 +212,14 @@
191212 	return idx2asid(asid) | generation;
192213 }
193214 
194
-void check_and_switch_context(struct mm_struct *mm, unsigned int cpu)
215
+void check_and_switch_context(struct mm_struct *mm)
195216 {
196217 	unsigned long flags;
218
+	unsigned int cpu;
197219 	u64 asid, old_active_asid;
220
+
221
+	if (system_supports_cnp())
222
+		cpu_set_reserved_ttbr0();
198223 
199224 	asid = atomic64_read(&mm->context.id);
200225 
....@@ -212,25 +237,25 @@
212237 	 *   relaxed xchg in flush_context will treat us as reserved
213238 	 *   because atomic RmWs are totally ordered for a given location.
214239 	 */
215
-	old_active_asid = atomic64_read(&per_cpu(active_asids, cpu));
216
-	if (old_active_asid &&
217
-	    !((asid ^ atomic64_read(&asid_generation)) >> asid_bits) &&
218
-	    atomic64_cmpxchg_relaxed(&per_cpu(active_asids, cpu),
240
+	old_active_asid = atomic64_read(this_cpu_ptr(&active_asids));
241
+	if (old_active_asid && asid_gen_match(asid) &&
242
+	    atomic64_cmpxchg_relaxed(this_cpu_ptr(&active_asids),
219243 				     old_active_asid, asid))
220244 		goto switch_mm_fastpath;
221245 
222246 	raw_spin_lock_irqsave(&cpu_asid_lock, flags);
223247 	/* Check that our ASID belongs to the current generation. */
224248 	asid = atomic64_read(&mm->context.id);
225
-	if ((asid ^ atomic64_read(&asid_generation)) >> asid_bits) {
226
-		asid = new_context(mm, cpu);
249
+	if (!asid_gen_match(asid)) {
250
+		asid = new_context(mm);
227251 		atomic64_set(&mm->context.id, asid);
228252 	}
229253 
254
+	cpu = smp_processor_id();
230255 	if (cpumask_test_and_clear_cpu(cpu, &tlb_flush_pending))
231256 		local_flush_tlb_all();
232257 
233
-	atomic64_set(&per_cpu(active_asids, cpu), asid);
258
+	atomic64_set(this_cpu_ptr(&active_asids), asid);
234259 	raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
235260 
236261 switch_mm_fastpath:
....@@ -245,23 +270,137 @@
245270 		cpu_switch_mm(mm->pgd, mm);
246271 }
247272 
273
+unsigned long arm64_mm_context_get(struct mm_struct *mm)
274
+{
275
+	unsigned long flags;
276
+	u64 asid;
277
+
278
+	if (!pinned_asid_map)
279
+		return 0;
280
+
281
+	raw_spin_lock_irqsave(&cpu_asid_lock, flags);
282
+
283
+	asid = atomic64_read(&mm->context.id);
284
+
285
+	if (refcount_inc_not_zero(&mm->context.pinned))
286
+		goto out_unlock;
287
+
288
+	if (nr_pinned_asids >= max_pinned_asids) {
289
+		asid = 0;
290
+		goto out_unlock;
291
+	}
292
+
293
+	if (!asid_gen_match(asid)) {
294
+		/*
295
+		 * We went through one or more rollover since that ASID was
296
+		 * used. Ensure that it is still valid, or generate a new one.
297
+		 */
298
+		asid = new_context(mm);
299
+		atomic64_set(&mm->context.id, asid);
300
+	}
301
+
302
+	nr_pinned_asids++;
303
+	__set_bit(asid2idx(asid), pinned_asid_map);
304
+	refcount_set(&mm->context.pinned, 1);
305
+
306
+out_unlock:
307
+	raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
308
+
309
+	asid &= ~ASID_MASK;
310
+
311
+	/* Set the equivalent of USER_ASID_BIT */
312
+	if (asid && arm64_kernel_unmapped_at_el0())
313
+		asid |= 1;
314
+
315
+	return asid;
316
+}
317
+EXPORT_SYMBOL_GPL(arm64_mm_context_get);
318
+
319
+void arm64_mm_context_put(struct mm_struct *mm)
320
+{
321
+	unsigned long flags;
322
+	u64 asid = atomic64_read(&mm->context.id);
323
+
324
+	if (!pinned_asid_map)
325
+		return;
326
+
327
+	raw_spin_lock_irqsave(&cpu_asid_lock, flags);
328
+
329
+	if (refcount_dec_and_test(&mm->context.pinned)) {
330
+		__clear_bit(asid2idx(asid), pinned_asid_map);
331
+		nr_pinned_asids--;
332
+	}
333
+
334
+	raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
335
+}
336
+EXPORT_SYMBOL_GPL(arm64_mm_context_put);
337
+
248338 /* Errata workaround post TTBRx_EL1 update. */
249339 asmlinkage void post_ttbr_update_workaround(void)
250340 {
341
+	if (!IS_ENABLED(CONFIG_CAVIUM_ERRATUM_27456))
342
+		return;
343
+
251344 	asm(ALTERNATIVE("nop; nop; nop",
252345 			"ic iallu; dsb nsh; isb",
253
-			ARM64_WORKAROUND_CAVIUM_27456,
254
-			CONFIG_CAVIUM_ERRATUM_27456));
346
+			ARM64_WORKAROUND_CAVIUM_27456));
255347 }
256348 
257
-static int asids_init(void)
349
+void cpu_do_switch_mm(phys_addr_t pgd_phys, struct mm_struct *mm)
258350 {
259
-	asid_bits = get_cpu_asid_bits();
351
+	unsigned long ttbr1 = read_sysreg(ttbr1_el1);
352
+	unsigned long asid = ASID(mm);
353
+	unsigned long ttbr0 = phys_to_ttbr(pgd_phys);
354
+
355
+	/* Skip CNP for the reserved ASID */
356
+	if (system_supports_cnp() && asid)
357
+		ttbr0 |= TTBR_CNP_BIT;
358
+
359
+	/* SW PAN needs a copy of the ASID in TTBR0 for entry */
360
+	if (IS_ENABLED(CONFIG_ARM64_SW_TTBR0_PAN))
361
+		ttbr0 |= FIELD_PREP(TTBR_ASID_MASK, asid);
362
+
363
+	/* Set ASID in TTBR1 since TCR.A1 is set */
364
+	ttbr1 &= ~TTBR_ASID_MASK;
365
+	ttbr1 |= FIELD_PREP(TTBR_ASID_MASK, asid);
366
+
367
+	write_sysreg(ttbr1, ttbr1_el1);
368
+	isb();
369
+	write_sysreg(ttbr0, ttbr0_el1);
370
+	isb();
371
+	post_ttbr_update_workaround();
372
+}
373
+
374
+static int asids_update_limit(void)
375
+{
376
+	unsigned long num_available_asids = NUM_USER_ASIDS;
377
+
378
+	if (arm64_kernel_unmapped_at_el0()) {
379
+		num_available_asids /= 2;
380
+		if (pinned_asid_map)
381
+			set_kpti_asid_bits(pinned_asid_map);
382
+	}
260383 	/*
261384 	 * Expect allocation after rollover to fail if we don't have at least
262385 	 * one more ASID than CPUs. ASID #0 is reserved for init_mm.
263386 	 */
264
-	WARN_ON(NUM_USER_ASIDS - 1 <= num_possible_cpus());
387
+	WARN_ON(num_available_asids - 1 <= num_possible_cpus());
388
+	pr_info("ASID allocator initialised with %lu entries\n",
389
+		num_available_asids);
390
+
391
+	/*
392
+	 * There must always be an ASID available after rollover. Ensure that,
393
+	 * even if all CPUs have a reserved ASID and the maximum number of ASIDs
394
+	 * are pinned, there still is at least one empty slot in the ASID map.
395
+	 */
396
+	max_pinned_asids = num_available_asids - num_possible_cpus() - 2;
397
+	return 0;
398
+}
399
+arch_initcall(asids_update_limit);
400
+
401
+static int asids_init(void)
402
+{
403
+	asid_bits = get_cpu_asid_bits();
265404 	atomic64_set(&asid_generation, ASID_FIRST_VERSION);
266405 	asid_map = kcalloc(BITS_TO_LONGS(NUM_USER_ASIDS), sizeof(*asid_map),
267406 			   GFP_KERNEL);
....@@ -269,7 +408,17 @@
269408 		panic("Failed to allocate bitmap for %lu ASIDs\n",
270409 		      NUM_USER_ASIDS);
271410 
272
-	pr_info("ASID allocator initialised with %lu entries\n", NUM_USER_ASIDS);
411
+	pinned_asid_map = kcalloc(BITS_TO_LONGS(NUM_USER_ASIDS),
412
+				  sizeof(*pinned_asid_map), GFP_KERNEL);
413
+	nr_pinned_asids = 0;
414
+
415
+	/*
416
+	 * We cannot call set_reserved_asid_bits() here because CPU
417
+	 * caps are not finalized yet, so it is safer to assume KPTI
418
+	 * and reserve kernel ASID's from beginning.
419
+	 */
420
+	if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0))
421
+		set_kpti_asid_bits(asid_map);
273422 	return 0;
274423 }
275424 early_initcall(asids_init);