1#include <linux/init.h>
2
3#include <linux/mm.h>
4#include <linux/spinlock.h>
5#include <linux/smp.h>
6#include <linux/interrupt.h>
7#include <linux/module.h>
8#include <linux/cpu.h>
9
10#include <asm/tlbflush.h>
11#include <asm/mmu_context.h>
12#include <asm/cache.h>
13#include <asm/apic.h>
14#include <asm/uv/uv.h>
15#include <linux/debugfs.h>
16
17/*
18 *	Smarter SMP flushing macros.
19 *		c/o Linus Torvalds.
20 *
21 *	These mean you can really definitely utterly forget about
22 *	writing to user space from interrupts. (Its not allowed anyway).
23 *
24 *	Optimizations Manfred Spraul <manfred@colorfullife.com>
25 *
26 *	More scalable flush, from Andi Kleen
27 *
28 *	Implement flush IPI by CALL_FUNCTION_VECTOR, Alex Shi
29 */
30
31struct flush_tlb_info {
32	struct mm_struct *flush_mm;
33	unsigned long flush_start;
34	unsigned long flush_end;
35};
36
37/*
38 * We cannot call mmdrop() because we are in interrupt context,
39 * instead update mm->cpu_vm_mask.
40 */
41void leave_mm(int cpu)
42{
43	struct mm_struct *active_mm = this_cpu_read(cpu_tlbstate.active_mm);
44	if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
45		BUG();
46	if (cpumask_test_cpu(cpu, mm_cpumask(active_mm))) {
47		cpumask_clear_cpu(cpu, mm_cpumask(active_mm));
48		load_cr3(swapper_pg_dir);
49		/*
50		 * This gets called in the idle path where RCU
51		 * functions differently.  Tracing normally
52		 * uses RCU, so we have to call the tracepoint
53		 * specially here.
54		 */
55		trace_tlb_flush_rcuidle(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
56	}
57}
58EXPORT_SYMBOL_GPL(leave_mm);
59
60/*
61 * The flush IPI assumes that a thread switch happens in this order:
62 * [cpu0: the cpu that switches]
63 * 1) switch_mm() either 1a) or 1b)
64 * 1a) thread switch to a different mm
65 * 1a1) set cpu_tlbstate to TLBSTATE_OK
66 *	Now the tlb flush NMI handler flush_tlb_func won't call leave_mm
67 *	if cpu0 was in lazy tlb mode.
68 * 1a2) update cpu active_mm
69 *	Now cpu0 accepts tlb flushes for the new mm.
70 * 1a3) cpu_set(cpu, new_mm->cpu_vm_mask);
71 *	Now the other cpus will send tlb flush ipis.
72 * 1a4) change cr3.
73 * 1a5) cpu_clear(cpu, old_mm->cpu_vm_mask);
74 *	Stop ipi delivery for the old mm. This is not synchronized with
75 *	the other cpus, but flush_tlb_func ignore flush ipis for the wrong
76 *	mm, and in the worst case we perform a superfluous tlb flush.
77 * 1b) thread switch without mm change
78 *	cpu active_mm is correct, cpu0 already handles flush ipis.
79 * 1b1) set cpu_tlbstate to TLBSTATE_OK
80 * 1b2) test_and_set the cpu bit in cpu_vm_mask.
81 *	Atomically set the bit [other cpus will start sending flush ipis],
82 *	and test the bit.
83 * 1b3) if the bit was 0: leave_mm was called, flush the tlb.
84 * 2) switch %%esp, ie current
85 *
86 * The interrupt must handle 2 special cases:
87 * - cr3 is changed before %%esp, ie. it cannot use current->{active_,}mm.
88 * - the cpu performs speculative tlb reads, i.e. even if the cpu only
89 *   runs in kernel space, the cpu could load tlb entries for user space
90 *   pages.
91 *
92 * The good news is that cpu_tlbstate is local to each cpu, no
93 * write/read ordering problems.
94 */
95
96/*
97 * TLB flush funcation:
98 * 1) Flush the tlb entries if the cpu uses the mm that's being flushed.
99 * 2) Leave the mm if we are in the lazy tlb mode.
100 */
101static void flush_tlb_func(void *info)
102{
103	struct flush_tlb_info *f = info;
104
105	inc_irq_stat(irq_tlb_count);
106
107	if (f->flush_mm != this_cpu_read(cpu_tlbstate.active_mm))
108		return;
109	if (!f->flush_end)
110		f->flush_end = f->flush_start + PAGE_SIZE;
111
112	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
113	if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK) {
114		if (f->flush_end == TLB_FLUSH_ALL) {
115			local_flush_tlb();
116			trace_tlb_flush(TLB_REMOTE_SHOOTDOWN, TLB_FLUSH_ALL);
117		} else {
118			unsigned long addr;
119			unsigned long nr_pages =
120				(f->flush_end - f->flush_start) / PAGE_SIZE;
121			addr = f->flush_start;
122			while (addr < f->flush_end) {
123				__flush_tlb_single(addr);
124				addr += PAGE_SIZE;
125			}
126			trace_tlb_flush(TLB_REMOTE_SHOOTDOWN, nr_pages);
127		}
128	} else
129		leave_mm(smp_processor_id());
130
131}
132
133void native_flush_tlb_others(const struct cpumask *cpumask,
134				 struct mm_struct *mm, unsigned long start,
135				 unsigned long end)
136{
137	struct flush_tlb_info info;
138	info.flush_mm = mm;
139	info.flush_start = start;
140	info.flush_end = end;
141
142	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
143	if (is_uv_system()) {
144		unsigned int cpu;
145
146		cpu = smp_processor_id();
147		cpumask = uv_flush_tlb_others(cpumask, mm, start, end, cpu);
148		if (cpumask)
149			smp_call_function_many(cpumask, flush_tlb_func,
150								&info, 1);
151		return;
152	}
153	smp_call_function_many(cpumask, flush_tlb_func, &info, 1);
154}
155
156void flush_tlb_current_task(void)
157{
158	struct mm_struct *mm = current->mm;
159
160	preempt_disable();
161
162	count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
163
164	/* This is an implicit full barrier that synchronizes with switch_mm. */
165	local_flush_tlb();
166
167	trace_tlb_flush(TLB_LOCAL_SHOOTDOWN, TLB_FLUSH_ALL);
168	if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
169		flush_tlb_others(mm_cpumask(mm), mm, 0UL, TLB_FLUSH_ALL);
170	preempt_enable();
171}
172
173/*
174 * See Documentation/x86/tlb.txt for details.  We choose 33
175 * because it is large enough to cover the vast majority (at
176 * least 95%) of allocations, and is small enough that we are
177 * confident it will not cause too much overhead.  Each single
178 * flush is about 100 ns, so this caps the maximum overhead at
179 * _about_ 3,000 ns.
180 *
181 * This is in units of pages.
182 */
183static unsigned long tlb_single_page_flush_ceiling __read_mostly = 33;
184
185void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
186				unsigned long end, unsigned long vmflag)
187{
188	unsigned long addr;
189	/* do a global flush by default */
190	unsigned long base_pages_to_flush = TLB_FLUSH_ALL;
191
192	preempt_disable();
193	if (current->active_mm != mm) {
194		/* Synchronize with switch_mm. */
195		smp_mb();
196
197		goto out;
198	}
199
200	if (!current->mm) {
201		leave_mm(smp_processor_id());
202
203		/* Synchronize with switch_mm. */
204		smp_mb();
205
206		goto out;
207	}
208
209	if ((end != TLB_FLUSH_ALL) && !(vmflag & VM_HUGETLB))
210		base_pages_to_flush = (end - start) >> PAGE_SHIFT;
211
212	/*
213	 * Both branches below are implicit full barriers (MOV to CR or
214	 * INVLPG) that synchronize with switch_mm.
215	 */
216	if (base_pages_to_flush > tlb_single_page_flush_ceiling) {
217		base_pages_to_flush = TLB_FLUSH_ALL;
218		count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
219		local_flush_tlb();
220	} else {
221		/* flush range by one by one 'invlpg' */
222		for (addr = start; addr < end;	addr += PAGE_SIZE) {
223			count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ONE);
224			__flush_tlb_single(addr);
225		}
226	}
227	trace_tlb_flush(TLB_LOCAL_MM_SHOOTDOWN, base_pages_to_flush);
228out:
229	if (base_pages_to_flush == TLB_FLUSH_ALL) {
230		start = 0UL;
231		end = TLB_FLUSH_ALL;
232	}
233	if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
234		flush_tlb_others(mm_cpumask(mm), mm, start, end);
235	preempt_enable();
236}
237
238void flush_tlb_page(struct vm_area_struct *vma, unsigned long start)
239{
240	struct mm_struct *mm = vma->vm_mm;
241
242	preempt_disable();
243
244	if (current->active_mm == mm) {
245		if (current->mm) {
246			/*
247			 * Implicit full barrier (INVLPG) that synchronizes
248			 * with switch_mm.
249			 */
250			__flush_tlb_one(start);
251		} else {
252			leave_mm(smp_processor_id());
253
254			/* Synchronize with switch_mm. */
255			smp_mb();
256		}
257	}
258
259	if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
260		flush_tlb_others(mm_cpumask(mm), mm, start, 0UL);
261
262	preempt_enable();
263}
264
265static void do_flush_tlb_all(void *info)
266{
267	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
268	__flush_tlb_all();
269	if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_LAZY)
270		leave_mm(smp_processor_id());
271}
272
273void flush_tlb_all(void)
274{
275	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
276	on_each_cpu(do_flush_tlb_all, NULL, 1);
277}
278
279static void do_kernel_range_flush(void *info)
280{
281	struct flush_tlb_info *f = info;
282	unsigned long addr;
283
284	/* flush range by one by one 'invlpg' */
285	for (addr = f->flush_start; addr < f->flush_end; addr += PAGE_SIZE)
286		__flush_tlb_single(addr);
287}
288
289void flush_tlb_kernel_range(unsigned long start, unsigned long end)
290{
291
292	/* Balance as user space task's flush, a bit conservative */
293	if (end == TLB_FLUSH_ALL ||
294	    (end - start) > tlb_single_page_flush_ceiling * PAGE_SIZE) {
295		on_each_cpu(do_flush_tlb_all, NULL, 1);
296	} else {
297		struct flush_tlb_info info;
298		info.flush_start = start;
299		info.flush_end = end;
300		on_each_cpu(do_kernel_range_flush, &info, 1);
301	}
302}
303
304static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf,
305			     size_t count, loff_t *ppos)
306{
307	char buf[32];
308	unsigned int len;
309
310	len = sprintf(buf, "%ld\n", tlb_single_page_flush_ceiling);
311	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
312}
313
314static ssize_t tlbflush_write_file(struct file *file,
315		 const char __user *user_buf, size_t count, loff_t *ppos)
316{
317	char buf[32];
318	ssize_t len;
319	int ceiling;
320
321	len = min(count, sizeof(buf) - 1);
322	if (copy_from_user(buf, user_buf, len))
323		return -EFAULT;
324
325	buf[len] = '\0';
326	if (kstrtoint(buf, 0, &ceiling))
327		return -EINVAL;
328
329	if (ceiling < 0)
330		return -EINVAL;
331
332	tlb_single_page_flush_ceiling = ceiling;
333	return count;
334}
335
336static const struct file_operations fops_tlbflush = {
337	.read = tlbflush_read_file,
338	.write = tlbflush_write_file,
339	.llseek = default_llseek,
340};
341
342static int __init create_tlb_single_page_flush_ceiling(void)
343{
344	debugfs_create_file("tlb_single_page_flush_ceiling", S_IRUSR | S_IWUSR,
345			    arch_debugfs_dir, NULL, &fops_tlbflush);
346	return 0;
347}
348late_initcall(create_tlb_single_page_flush_ceiling);
349