1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Miscellaneous cgroup controller
  4 *
  5 * Copyright 2020 Google LLC
  6 * Author: Vipin Sharma <vipinsh@google.com>
  7 */
  8
  9#include <linux/limits.h>
 10#include <linux/cgroup.h>
 11#include <linux/errno.h>
 12#include <linux/atomic.h>
 13#include <linux/slab.h>
 14#include <linux/misc_cgroup.h>
 15
 16#define MAX_STR "max"
 17#define MAX_NUM ULONG_MAX
 18
 19/* Miscellaneous res name, keep it in sync with enum misc_res_type */
 20static const char *const misc_res_name[] = {
 21#ifdef CONFIG_KVM_AMD_SEV
 22	/* AMD SEV ASIDs resource */
 23	"sev",
 24	/* AMD SEV-ES ASIDs resource */
 25	"sev_es",
 26#endif
 27};
 28
 29/* Root misc cgroup */
 30static struct misc_cg root_cg;
 31
 32/*
 33 * Miscellaneous resources capacity for the entire machine. 0 capacity means
 34 * resource is not initialized or not present in the host.
 35 *
 36 * root_cg.max and capacity are independent of each other. root_cg.max can be
 37 * more than the actual capacity. We are using Limits resource distribution
 38 * model of cgroup for miscellaneous controller.
 39 */
 40static unsigned long misc_res_capacity[MISC_CG_RES_TYPES];
 41
 42/**
 43 * parent_misc() - Get the parent of the passed misc cgroup.
 44 * @cgroup: cgroup whose parent needs to be fetched.
 45 *
 46 * Context: Any context.
 47 * Return:
 48 * * struct misc_cg* - Parent of the @cgroup.
 49 * * %NULL - If @cgroup is null or the passed cgroup does not have a parent.
 50 */
 51static struct misc_cg *parent_misc(struct misc_cg *cgroup)
 52{
 53	return cgroup ? css_misc(cgroup->css.parent) : NULL;
 54}
 55
 56/**
 57 * valid_type() - Check if @type is valid or not.
 58 * @type: misc res type.
 59 *
 60 * Context: Any context.
 61 * Return:
 62 * * true - If valid type.
 63 * * false - If not valid type.
 64 */
 65static inline bool valid_type(enum misc_res_type type)
 66{
 67	return type >= 0 && type < MISC_CG_RES_TYPES;
 68}
 69
 70/**
 71 * misc_cg_res_total_usage() - Get the current total usage of the resource.
 72 * @type: misc res type.
 73 *
 74 * Context: Any context.
 75 * Return: Current total usage of the resource.
 76 */
 77unsigned long misc_cg_res_total_usage(enum misc_res_type type)
 78{
 79	if (valid_type(type))
 80		return atomic_long_read(&root_cg.res[type].usage);
 81
 82	return 0;
 83}
 84EXPORT_SYMBOL_GPL(misc_cg_res_total_usage);
 85
 86/**
 87 * misc_cg_set_capacity() - Set the capacity of the misc cgroup res.
 88 * @type: Type of the misc res.
 89 * @capacity: Supported capacity of the misc res on the host.
 90 *
 91 * If capacity is 0 then the charging a misc cgroup fails for that type.
 92 *
 93 * Context: Any context.
 94 * Return:
 95 * * %0 - Successfully registered the capacity.
 96 * * %-EINVAL - If @type is invalid.
 97 */
 98int misc_cg_set_capacity(enum misc_res_type type, unsigned long capacity)
 99{
100	if (!valid_type(type))
101		return -EINVAL;
102
103	WRITE_ONCE(misc_res_capacity[type], capacity);
104	return 0;
105}
106EXPORT_SYMBOL_GPL(misc_cg_set_capacity);
107
108/**
109 * misc_cg_cancel_charge() - Cancel the charge from the misc cgroup.
110 * @type: Misc res type in misc cg to cancel the charge from.
111 * @cg: Misc cgroup to cancel charge from.
112 * @amount: Amount to cancel.
113 *
114 * Context: Any context.
115 */
116static void misc_cg_cancel_charge(enum misc_res_type type, struct misc_cg *cg,
117				  unsigned long amount)
118{
119	WARN_ONCE(atomic_long_add_negative(-amount, &cg->res[type].usage),
120		  "misc cgroup resource %s became less than 0",
121		  misc_res_name[type]);
122}
123
124/**
125 * misc_cg_try_charge() - Try charging the misc cgroup.
126 * @type: Misc res type to charge.
127 * @cg: Misc cgroup which will be charged.
128 * @amount: Amount to charge.
129 *
130 * Charge @amount to the misc cgroup. Caller must use the same cgroup during
131 * the uncharge call.
132 *
133 * Context: Any context.
134 * Return:
135 * * %0 - If successfully charged.
136 * * -EINVAL - If @type is invalid or misc res has 0 capacity.
137 * * -EBUSY - If max limit will be crossed or total usage will be more than the
138 *	      capacity.
139 */
140int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg,
141		       unsigned long amount)
142{
143	struct misc_cg *i, *j;
144	int ret;
145	struct misc_res *res;
146	int new_usage;
147
148	if (!(valid_type(type) && cg && READ_ONCE(misc_res_capacity[type])))
149		return -EINVAL;
150
151	if (!amount)
152		return 0;
153
154	for (i = cg; i; i = parent_misc(i)) {
155		res = &i->res[type];
156
157		new_usage = atomic_long_add_return(amount, &res->usage);
158		if (new_usage > READ_ONCE(res->max) ||
159		    new_usage > READ_ONCE(misc_res_capacity[type])) {
160			if (!res->failed) {
161				pr_info("cgroup: charge rejected by the misc controller for %s resource in ",
162					misc_res_name[type]);
163				pr_cont_cgroup_path(i->css.cgroup);
164				pr_cont("\n");
165				res->failed = true;
166			}
167			ret = -EBUSY;
168			goto err_charge;
169		}
170	}
171	return 0;
172
173err_charge:
174	for (j = cg; j != i; j = parent_misc(j))
175		misc_cg_cancel_charge(type, j, amount);
176	misc_cg_cancel_charge(type, i, amount);
177	return ret;
178}
179EXPORT_SYMBOL_GPL(misc_cg_try_charge);
180
181/**
182 * misc_cg_uncharge() - Uncharge the misc cgroup.
183 * @type: Misc res type which was charged.
184 * @cg: Misc cgroup which will be uncharged.
185 * @amount: Charged amount.
186 *
187 * Context: Any context.
188 */
189void misc_cg_uncharge(enum misc_res_type type, struct misc_cg *cg,
190		      unsigned long amount)
191{
192	struct misc_cg *i;
193
194	if (!(amount && valid_type(type) && cg))
195		return;
196
197	for (i = cg; i; i = parent_misc(i))
198		misc_cg_cancel_charge(type, i, amount);
199}
200EXPORT_SYMBOL_GPL(misc_cg_uncharge);
201
202/**
203 * misc_cg_max_show() - Show the misc cgroup max limit.
204 * @sf: Interface file
205 * @v: Arguments passed
206 *
207 * Context: Any context.
208 * Return: 0 to denote successful print.
209 */
210static int misc_cg_max_show(struct seq_file *sf, void *v)
211{
212	int i;
213	struct misc_cg *cg = css_misc(seq_css(sf));
214	unsigned long max;
215
216	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
217		if (READ_ONCE(misc_res_capacity[i])) {
218			max = READ_ONCE(cg->res[i].max);
219			if (max == MAX_NUM)
220				seq_printf(sf, "%s max\n", misc_res_name[i]);
221			else
222				seq_printf(sf, "%s %lu\n", misc_res_name[i],
223					   max);
224		}
225	}
226
227	return 0;
228}
229
230/**
231 * misc_cg_max_write() - Update the maximum limit of the cgroup.
232 * @of: Handler for the file.
233 * @buf: Data from the user. It should be either "max", 0, or a positive
234 *	 integer.
235 * @nbytes: Number of bytes of the data.
236 * @off: Offset in the file.
237 *
238 * User can pass data like:
239 * echo sev 23 > misc.max, OR
240 * echo sev max > misc.max
241 *
242 * Context: Any context.
243 * Return:
244 * * >= 0 - Number of bytes processed in the input.
245 * * -EINVAL - If buf is not valid.
246 * * -ERANGE - If number is bigger than the unsigned long capacity.
247 */
248static ssize_t misc_cg_max_write(struct kernfs_open_file *of, char *buf,
249				 size_t nbytes, loff_t off)
250{
251	struct misc_cg *cg;
252	unsigned long max;
253	int ret = 0, i;
254	enum misc_res_type type = MISC_CG_RES_TYPES;
255	char *token;
256
257	buf = strstrip(buf);
258	token = strsep(&buf, " ");
259
260	if (!token || !buf)
261		return -EINVAL;
262
263	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
264		if (!strcmp(misc_res_name[i], token)) {
265			type = i;
266			break;
267		}
268	}
269
270	if (type == MISC_CG_RES_TYPES)
271		return -EINVAL;
272
273	if (!strcmp(MAX_STR, buf)) {
274		max = MAX_NUM;
275	} else {
276		ret = kstrtoul(buf, 0, &max);
277		if (ret)
278			return ret;
279	}
280
281	cg = css_misc(of_css(of));
282
283	if (READ_ONCE(misc_res_capacity[type]))
284		WRITE_ONCE(cg->res[type].max, max);
285	else
286		ret = -EINVAL;
287
288	return ret ? ret : nbytes;
289}
290
291/**
292 * misc_cg_current_show() - Show the current usage of the misc cgroup.
293 * @sf: Interface file
294 * @v: Arguments passed
295 *
296 * Context: Any context.
297 * Return: 0 to denote successful print.
298 */
299static int misc_cg_current_show(struct seq_file *sf, void *v)
300{
301	int i;
302	unsigned long usage;
303	struct misc_cg *cg = css_misc(seq_css(sf));
304
305	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
306		usage = atomic_long_read(&cg->res[i].usage);
307		if (READ_ONCE(misc_res_capacity[i]) || usage)
308			seq_printf(sf, "%s %lu\n", misc_res_name[i], usage);
309	}
310
311	return 0;
312}
313
314/**
315 * misc_cg_capacity_show() - Show the total capacity of misc res on the host.
316 * @sf: Interface file
317 * @v: Arguments passed
318 *
319 * Only present in the root cgroup directory.
320 *
321 * Context: Any context.
322 * Return: 0 to denote successful print.
323 */
324static int misc_cg_capacity_show(struct seq_file *sf, void *v)
325{
326	int i;
327	unsigned long cap;
328
329	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
330		cap = READ_ONCE(misc_res_capacity[i]);
331		if (cap)
332			seq_printf(sf, "%s %lu\n", misc_res_name[i], cap);
333	}
334
335	return 0;
336}
337
338/* Misc cgroup interface files */
339static struct cftype misc_cg_files[] = {
340	{
341		.name = "max",
342		.write = misc_cg_max_write,
343		.seq_show = misc_cg_max_show,
344		.flags = CFTYPE_NOT_ON_ROOT,
345	},
346	{
347		.name = "current",
348		.seq_show = misc_cg_current_show,
349		.flags = CFTYPE_NOT_ON_ROOT,
350	},
351	{
352		.name = "capacity",
353		.seq_show = misc_cg_capacity_show,
354		.flags = CFTYPE_ONLY_ON_ROOT,
355	},
356	{}
357};
358
359/**
360 * misc_cg_alloc() - Allocate misc cgroup.
361 * @parent_css: Parent cgroup.
362 *
363 * Context: Process context.
364 * Return:
365 * * struct cgroup_subsys_state* - css of the allocated cgroup.
366 * * ERR_PTR(-ENOMEM) - No memory available to allocate.
367 */
368static struct cgroup_subsys_state *
369misc_cg_alloc(struct cgroup_subsys_state *parent_css)
370{
371	enum misc_res_type i;
372	struct misc_cg *cg;
373
374	if (!parent_css) {
375		cg = &root_cg;
376	} else {
377		cg = kzalloc(sizeof(*cg), GFP_KERNEL);
378		if (!cg)
379			return ERR_PTR(-ENOMEM);
380	}
381
382	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
383		WRITE_ONCE(cg->res[i].max, MAX_NUM);
384		atomic_long_set(&cg->res[i].usage, 0);
385	}
386
387	return &cg->css;
388}
389
390/**
391 * misc_cg_free() - Free the misc cgroup.
392 * @css: cgroup subsys object.
393 *
394 * Context: Any context.
395 */
396static void misc_cg_free(struct cgroup_subsys_state *css)
397{
398	kfree(css_misc(css));
399}
400
401/* Cgroup controller callbacks */
402struct cgroup_subsys misc_cgrp_subsys = {
403	.css_alloc = misc_cg_alloc,
404	.css_free = misc_cg_free,
405	.legacy_cftypes = misc_cg_files,
406	.dfl_cftypes = misc_cg_files,
407};