Message-Id: <20210218195549.1696769-2-vipinsh@google.com>
Date:   Thu, 18 Feb 2021 11:55:48 -0800
From:   Vipin Sharma <vipinsh@...gle.com>
To:     tj@...nel.org, thomas.lendacky@....com, brijesh.singh@....com,
        jon.grimm@....com, eric.vantassell@....com, pbonzini@...hat.com,
        hannes@...xchg.org, frankja@...ux.ibm.com, borntraeger@...ibm.com
Cc:     corbet@....net, seanjc@...gle.com, vkuznets@...hat.com,
        wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        gingell@...gle.com, rientjes@...gle.com, dionnaglaze@...gle.com,
        kvm@...r.kernel.org, x86@...nel.org, cgroups@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Vipin Sharma <vipinsh@...gle.com>
Subject: [RFC 1/2] cgroup: sev: Add misc cgroup controller

The Miscellaneous cgroup provides the resource allocation and tracking
mechanism for the scalar resources which cannot be abstracted like the
other cgroup resources. Controller is enabled by the CONFIG_CGROUP_MISC
config option.

The first two resources added to the miscellaneous controller are Secure
Encrypted Virtualization (SEV) ASIDs and SEV - Encrypted State (SEV-ES)
ASIDs. These limited ASIDs are used for encrypting virtual machines
memory on the AMD platform

Miscellaneous controller provides 3 interface files:

misc.capacity
  A read-only flat-keyed file shown only in the root cgroup.  It shows
  miscellaneous scalar resources available on the platform along with
  their quantities
	$ cat misc.capacity
	sev 50
	sev_es 10

misc.current
  A read-only flat-keyed file shown in the non-root cgroups.  It shows
  the current usage of the resources in the cgroup and its children.
	$ cat misc.current
	sev 3
	sev_es 0

misc.max
  A read-write flat-keyed file shown in the non root cgroups. Allowed
  maximum usage of the resources in the cgroup and its children.::
	$ cat misc.max
	sev max
	sev_es 4

  Limit can be set by::
	# echo sev 1 > misc.max

  Limit can be set to max by::
	# echo sev max > misc.max

  Limits can be set more than the capacity value in the misc.capacity
  file.

Signed-off-by: Vipin Sharma <vipinsh@...gle.com>
Reviewed-by: David Rientjes <rientjes@...gle.com>
---
 arch/x86/kvm/svm/sev.c        |  60 ++++-
 arch/x86/kvm/svm/svm.h        |   1 +
 include/linux/cgroup_subsys.h |   4 +
 include/linux/misc_cgroup.h   |  75 ++++++
 init/Kconfig                  |  14 ++
 kernel/cgroup/Makefile        |   1 +
 kernel/cgroup/misc.c          | 456 ++++++++++++++++++++++++++++++++++
 7 files changed, 601 insertions(+), 10 deletions(-)
 create mode 100644 include/linux/misc_cgroup.h
 create mode 100644 kernel/cgroup/misc.c

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 48017fef1cd9..1617bb2ce83e 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -14,6 +14,7 @@
 #include <linux/psp-sev.h>
 #include <linux/pagemap.h>
 #include <linux/swap.h>
+#include <linux/misc_cgroup.h>
 #include <linux/processor.h>
 #include <linux/trace_events.h>
 #include <asm/fpu/internal.h>
@@ -27,6 +28,21 @@
 
 #define __ex(x) __kvm_handle_fault_on_reboot(x)
 
+#ifndef CONFIG_KVM_AMD_SEV
+/*
+ * When this config is not defined, SEV feature is not supported and APIs in
+ * this file are not used but this file still gets compiled into the KVM AMD
+ * module.
+ *
+ * We will not have MISC_CG_RES_SEV and MISC_CG_RES_SEV_ES entries in the enum
+ * misc_res_type {} defined in linux/misc_cgroup.h.
+ *
+ * Below macros allow compilation to succeed.
+ */
+#define MISC_CG_RES_SEV MISC_CG_RES_TYPES
+#define MISC_CG_RES_SEV_ES MISC_CG_RES_TYPES
+#endif
+
 static u8 sev_enc_bit;
 static int sev_flush_asids(void);
 static DECLARE_RWSEM(sev_deactivate_lock);
@@ -88,8 +104,14 @@ static bool __sev_recycle_asids(int min_asid, int max_asid)
 
 static int sev_asid_new(struct kvm_sev_info *sev)
 {
-	int pos, min_asid, max_asid;
+	int pos, min_asid, max_asid, ret;
 	bool retry = true;
+	enum misc_res_type type;
+
+	type = sev->es_active ? MISC_CG_RES_SEV_ES : MISC_CG_RES_SEV;
+	ret = misc_cg_try_charge(type, &sev->misc_cg, 1);
+	if (ret)
+		return ret;
 
 	mutex_lock(&sev_bitmap_lock);
 
@@ -107,7 +129,8 @@ static int sev_asid_new(struct kvm_sev_info *sev)
 			goto again;
 		}
 		mutex_unlock(&sev_bitmap_lock);
-		return -EBUSY;
+		ret = -EBUSY;
+		goto e_uncharge;
 	}
 
 	__set_bit(pos, sev_asid_bitmap);
@@ -115,6 +138,9 @@ static int sev_asid_new(struct kvm_sev_info *sev)
 	mutex_unlock(&sev_bitmap_lock);
 
 	return pos + 1;
+e_uncharge:
+	misc_cg_uncharge(type, sev->misc_cg, 1);
+	return ret;
 }
 
 static int sev_get_asid(struct kvm *kvm)
@@ -124,14 +150,15 @@ static int sev_get_asid(struct kvm *kvm)
 	return sev->asid;
 }
 
-static void sev_asid_free(int asid)
+static void sev_asid_free(struct kvm_sev_info *sev)
 {
 	struct svm_cpu_data *sd;
 	int cpu, pos;
+	enum misc_res_type type;
 
 	mutex_lock(&sev_bitmap_lock);
 
-	pos = asid - 1;
+	pos = sev->asid - 1;
 	__set_bit(pos, sev_reclaim_asid_bitmap);
 
 	for_each_possible_cpu(cpu) {
@@ -140,6 +167,9 @@ static void sev_asid_free(int asid)
 	}
 
 	mutex_unlock(&sev_bitmap_lock);
+
+	type = sev->es_active ? MISC_CG_RES_SEV_ES : MISC_CG_RES_SEV;
+	misc_cg_uncharge(type, sev->misc_cg, 1);
 }
 
 static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
@@ -187,19 +217,19 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	asid = sev_asid_new(sev);
 	if (asid < 0)
 		return ret;
+	sev->asid = asid;
 
 	ret = sev_platform_init(&argp->error);
 	if (ret)
 		goto e_free;
 
 	sev->active = true;
-	sev->asid = asid;
 	INIT_LIST_HEAD(&sev->regions_list);
 
 	return 0;
 
 e_free:
-	sev_asid_free(asid);
+	sev_asid_free(sev);
 	return ret;
 }
 
@@ -1243,12 +1273,12 @@ void sev_vm_destroy(struct kvm *kvm)
 	mutex_unlock(&kvm->lock);
 
 	sev_unbind_asid(kvm, sev->handle);
-	sev_asid_free(sev->asid);
+	sev_asid_free(sev);
 }
 
 void __init sev_hardware_setup(void)
 {
-	unsigned int eax, ebx, ecx, edx;
+	unsigned int eax, ebx, ecx, edx, sev_asid_count, sev_es_asid_count;
 	bool sev_es_supported = false;
 	bool sev_supported = false;
 
@@ -1280,7 +1310,11 @@ void __init sev_hardware_setup(void)
 	if (!sev_reclaim_asid_bitmap)
 		goto out;
 
-	pr_info("SEV supported: %u ASIDs\n", max_sev_asid - min_sev_asid + 1);
+	sev_asid_count = max_sev_asid - min_sev_asid + 1;
+	if (misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count))
+		goto out;
+
+	pr_info("SEV supported: %u ASIDs\n", sev_asid_count);
 	sev_supported = true;
 
 	/* SEV-ES support requested? */
@@ -1295,7 +1329,11 @@ void __init sev_hardware_setup(void)
 	if (min_sev_asid == 1)
 		goto out;
 
-	pr_info("SEV-ES supported: %u ASIDs\n", min_sev_asid - 1);
+	sev_es_asid_count = min_sev_asid - 1;
+	if (misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count))
+		goto out;
+
+	pr_info("SEV-ES supported: %u ASIDs\n", sev_es_asid_count);
 	sev_es_supported = true;
 
 out:
@@ -1310,6 +1348,8 @@ void sev_hardware_teardown(void)
 
 	bitmap_free(sev_asid_bitmap);
 	bitmap_free(sev_reclaim_asid_bitmap);
+	misc_cg_set_capacity(MISC_CG_RES_SEV, 0);
+	misc_cg_set_capacity(MISC_CG_RES_SEV_ES, 0);
 
 	sev_flush_asids();
 }
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 6e7d070f8b86..8ed6ebf47885 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -79,6 +79,7 @@ struct kvm_sev_info {
 	unsigned long pages_locked; /* Number of pages locked */
 	struct list_head regions_list;  /* List of registered regions */
 	u64 ap_jump_table;	/* SEV-ES AP Jump Table address */
+	struct misc_cg *misc_cg; /* For misc cgroup accounting */
 };
 
 struct kvm_svm {
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index acb77dcff3b4..445235487230 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -61,6 +61,10 @@ SUBSYS(pids)
 SUBSYS(rdma)
 #endif
 
+#if IS_ENABLED(CONFIG_CGROUP_MISC)
+SUBSYS(misc)
+#endif
+
 /*
  * The following subsystems are not supported on the default hierarchy.
  */
diff --git a/include/linux/misc_cgroup.h b/include/linux/misc_cgroup.h
new file mode 100644
index 000000000000..157859f2f108
--- /dev/null
+++ b/include/linux/misc_cgroup.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Miscellaneous cgroup controller.
+ *
+ * Copyright 2020 Google LLC
+ * Author: Vipin Sharma <vipinsh@...gle.com>
+ */
+#ifndef _MISC_CGROUP_H_
+#define _MISC_CGROUP_H_
+
+/**
+ * Types of misc cgroup entries supported by the host.
+ */
+enum misc_res_type {
+#ifdef CONFIG_KVM_AMD_SEV
+	/* AMD SEV ASIDs resource */
+	MISC_CG_RES_SEV,
+	/* AMD SEV-ES ASIDs resource */
+	MISC_CG_RES_SEV_ES,
+#endif
+	MISC_CG_RES_TYPES
+};
+
+struct misc_cg;
+
+#ifdef CONFIG_CGROUP_MISC
+
+/**
+ * struct misc_res: Per cgroup per misc type resource
+ * @max: Maximum count of the resource.
+ * @usage: Current usage of the resource.
+ */
+struct misc_res {
+	unsigned int max;
+	atomic_t usage;
+};
+
+/**
+ * struct misc_cg - Miscellaneous controller's cgroup structure.
+ * @css: cgroup subsys state object.
+ * @res: Array of misc resources usage in the cgroup.
+ */
+struct misc_cg {
+	struct cgroup_subsys_state css;
+	struct misc_res res[MISC_CG_RES_TYPES];
+};
+
+int misc_cg_set_capacity(enum misc_res_type type, unsigned int capacity);
+int misc_cg_try_charge(enum misc_res_type type, struct misc_cg **cg,
+		       unsigned int amount);
+void misc_cg_uncharge(enum misc_res_type type, struct misc_cg *cg,
+		      unsigned int amount);
+
+#else /* !CONFIG_CGROUP_MISC */
+
+static inline int misc_cg_set_capacity(enum misc_res_type type,
+				       unsigned int capacity)
+{
+	return 0;
+}
+
+static inline int misc_cg_try_charge(enum misc_res_type type,
+				     struct misc_cg **cg,
+				     unsigned int amount)
+{
+	return 0;
+}
+
+static inline void misc_cg_uncharge(enum misc_res_type type,
+				    struct misc_cg *cg,
+				    unsigned int amount)
+{
+}
+#endif /* CONFIG_CGROUP_MISC */
+#endif /* _MISC_CGROUP_H_ */
diff --git a/init/Kconfig b/init/Kconfig
index 29ad68325028..0b392135e555 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1105,6 +1105,20 @@ config CGROUP_BPF
 	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
 	  inet sockets.
 
+config CGROUP_MISC
+	bool "Misc resource controller"
+	default n
+	help
+	  Provides a controller for miscellaneous resources on a host.
+
+	  Miscellaneous scalar resources are the resources on the host system
+	  which cannot be abstracted like the other cgroups. This controller
+	  tracks and limits the miscellaneous resources used by a process
+	  attached to a cgroup hierarchy.
+
+	  For more information, please check misc cgroup section in
+	  /Documentation/admin-guide/cgroup-v2.rst.
+
 config CGROUP_DEBUG
 	bool "Debug controller"
 	default n
diff --git a/kernel/cgroup/Makefile b/kernel/cgroup/Makefile
index 5d7a76bfbbb7..12f8457ad1f9 100644
--- a/kernel/cgroup/Makefile
+++ b/kernel/cgroup/Makefile
@@ -5,4 +5,5 @@ obj-$(CONFIG_CGROUP_FREEZER) += legacy_freezer.o
 obj-$(CONFIG_CGROUP_PIDS) += pids.o
 obj-$(CONFIG_CGROUP_RDMA) += rdma.o
 obj-$(CONFIG_CPUSETS) += cpuset.o
+obj-$(CONFIG_CGROUP_MISC) += misc.o
 obj-$(CONFIG_CGROUP_DEBUG) += debug.o
diff --git a/kernel/cgroup/misc.c b/kernel/cgroup/misc.c
new file mode 100644
index 000000000000..9e4ad4c3dbcc
--- /dev/null
+++ b/kernel/cgroup/misc.c
@@ -0,0 +1,456 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Miscellaneous cgroup controller
+ *
+ * Copyright 2020 Google LLC
+ * Author: Vipin Sharma <vipinsh@...gle.com>
+ */
+
+#include <linux/limits.h>
+#include <linux/cgroup.h>
+#include <linux/errno.h>
+#include <linux/atomic.h>
+#include <linux/slab.h>
+#include <linux/misc_cgroup.h>
+
+#define MAX_STR "max"
+#define MAX_NUM UINT_MAX
+
+/* Miscellaneous res name, keep it in sync with enum misc_res_type */
+static const char *const misc_res_name[] = {
+#ifdef CONFIG_KVM_AMD_SEV
+	"sev",
+	"sev_es",
+#endif
+};
+
+/* Root misc cgroup */
+static struct misc_cg root_cg;
+
+/*
+ * Miscellaneous resources capacity for the entire machine. 0 capacity means
+ * resource is not initialized or not present in the host.
+ *
+ * root_cg.max and capacity are independent of each other. root_cg.max can be
+ * more than the actual capacity. We are using Limits resource distribution
+ * model of cgroup for miscellaneous controller. However, root_cg.current for a
+ * resource will never exceeds the resource capacity.
+ */
+static unsigned int misc_res_capacity[MISC_CG_RES_TYPES];
+
+/**
+ * css_misc() - Get misc cgroup from the css.
+ * @css: cgroup subsys state object.
+ *
+ * Context: Any context.
+ * Return:
+ * * %NULL - If @css is null.
+ * * struct misc_cg* - misc cgroup pointer of the passed css.
+ */
+static struct misc_cg *css_misc(struct cgroup_subsys_state *css)
+{
+	return css ? container_of(css, struct misc_cg, css) : NULL;
+}
+
+/**
+ * parent_misc() - Get the parent of the passed misc cgroup.
+ * @cgroup: cgroup whose parent needs to be fetched.
+ *
+ * Context: Any context.
+ * Return:
+ * * struct misc_cg* - Parent of the @cgroup.
+ * * %NULL - If @cgroup is null or the passed cgroup does not have a parent.
+ */
+static struct misc_cg *parent_misc(struct misc_cg *cgroup)
+{
+	return cgroup ? css_misc(cgroup->css.parent) : NULL;
+}
+
+/**
+ * valid_type() - Check if @type is valid or not.
+ * @type: misc res type.
+ *
+ * Context: Any context.
+ * Return:
+ * * true - If valid type.
+ * * false - If not valid type.
+ */
+static inline bool valid_type(enum misc_res_type type)
+{
+	return type >= 0 && type < MISC_CG_RES_TYPES;
+}
+
+/**
+ * misc_cg_uncharge_hierarchy() - Uncharge the misc cgroup hierarchy.
+ * @start_cg: Start cgroup.
+ * @stop_cg: End cgroup.
+ * @type: type of misc res to uncharge.
+ * @amount: Charge amount.
+ *
+ * Uncharge the cgroup tree from the given start cgroup to the stop cgroup.
+ *
+ * Context: Any context.
+ */
+static void misc_cg_uncharge_hierarchy(enum misc_res_type type,
+				       struct misc_cg *start_cg,
+				       struct misc_cg *stop_cg,
+				       unsigned int amount)
+{
+	struct misc_cg *i;
+	int usage;
+
+	for (i = start_cg; i != stop_cg; i = parent_misc(i)) {
+		usage = atomic_sub_return(amount, &i->res[type].usage);
+
+		// Last one to uncharge puts the reference.
+		if (usage == 0)
+			css_put(&i->css);
+
+		WARN_ONCE(usage < 0,
+			  "misc cgroup resource %s became less than 0",
+			  misc_res_name[type]);
+	}
+
+	if (stop_cg) {
+		usage = atomic_sub_return(amount, &stop_cg->res[type].usage);
+		WARN_ONCE(usage < 0,
+			  "misc cgroup resource %s became less than 0",
+			  misc_res_name[type]);
+	}
+}
+
+/**
+ * misc_cg_set_capacity() - Set the capacity of the misc cgroup res.
+ * @type: Type of the misc res.
+ * @capacity: Supported capacity of the misc res on the host.
+ *
+ * If capacity is 0 then the charging a misc cgroup fails for that type.
+ *
+ * The caller must serialize invocations on the same resource.
+ *
+ * Context: Process context.
+ * Return:
+ * * %0 - Successfully registered the capacity.
+ * * %-EINVAL - If @type is invalid.
+ * * %-EBUSY - If current usage is more than the capacity.
+ */
+int misc_cg_set_capacity(enum misc_res_type type, unsigned int capacity)
+{
+	if (!valid_type(type))
+		return -EINVAL;
+
+	for (;;) {
+		int usage;
+		unsigned int old;
+
+		/*
+		 * Update the capacity while making sure that it's not below
+		 * the concurrently-changing usage value.
+		 *
+		 * The xchg implies two full memory barriers before and after,
+		 * so the read-swap-read is ordered and ensures coherency with
+		 * misc_cg_try_charge(): that function modifies the usage
+		 * before checking the capacity, so if it sees the old
+		 * capacity, we see the modified usage and retry.
+		 */
+		usage = atomic_read(&root_cg.res[type].usage);
+
+		if (usage > capacity)
+			return -EBUSY;
+
+		old = xchg(&misc_res_capacity[type], capacity);
+
+		if (atomic_read(&root_cg.res[type].usage) <= usage)
+			return 0;
+
+		misc_res_capacity[type] = old;
+		cond_resched();
+	}
+}
+EXPORT_SYMBOL(misc_cg_set_capacity);
+
+/**
+ * misc_cg_try_charge() - Try charging misc cgroup.
+ * @type: misc res type to charge.
+ * @cg: Misc cgroup which will be charged, out parameter.
+ * @amount: Amount to charge.
+ *
+ * Charge @amount to the cgroup to which the current task belongs to. Charged
+ * cgroup will be pointed by @cg. Caller must use the same cgroup during
+ * uncharge call.
+ *
+ * Context: Any context.
+ * Return:
+ * * %0 - If successfully charged.
+ * * -EINVAL - If @type is invalid or misc res has 0 capacity.
+ * * -EBUSY - If max limit will be crossed or total usage will be more than the
+ *	      capacity.
+ */
+int misc_cg_try_charge(enum misc_res_type type, struct misc_cg **cg,
+		       unsigned int amount)
+{
+	struct misc_cg *task_cg, *i;
+	int ret;
+	struct misc_res *res;
+	int new_usage;
+
+	if (!(valid_type(type) && cg && misc_res_capacity[type]))
+		return -EINVAL;
+
+	if (!amount)
+		return 0;
+
+	task_cg = css_misc(task_get_css(current, misc_cgrp_id));
+
+	for (i = task_cg; i; i = parent_misc(i)) {
+		res = &i->res[type];
+
+		/*
+		 * The atomic_long_add_return() implies a full memory barrier
+		 * between incrementing the count and reading the capacity.
+		 * When racing with misc_cg_set_capacity(), we either see the
+		 * new capacity or the setter sees the counter has changed and
+		 * retries.
+		 */
+		new_usage = atomic_add_return(amount, &res->usage);
+		if (new_usage > res->max ||
+		    new_usage > misc_res_capacity[type]) {
+			ret = -EBUSY;
+			goto err_charge;
+		}
+
+		// First one to charge gets a reference.
+		if (new_usage == amount)
+			css_get(&i->css);
+	}
+
+	*cg = task_cg;
+	css_put(&task_cg->css);
+	return 0;
+
+err_charge:
+	misc_cg_uncharge_hierarchy(type, task_cg, i, amount);
+	css_put(&task_cg->css);
+	return ret;
+}
+EXPORT_SYMBOL(misc_cg_try_charge);
+
+/**
+ * misc_cg_uncharge() - Uncharge the misc cgroup.
+ * @type: Misc res type which was charged.
+ * @cg: Misc cgroup which will be uncharged.
+ * @amount: Charged amount.
+ *
+ * Context: Any context.
+ */
+void misc_cg_uncharge(enum misc_res_type type, struct misc_cg *cg,
+		      unsigned int amount)
+{
+	if (amount && valid_type(type) && cg)
+		misc_cg_uncharge_hierarchy(type, cg, NULL, amount);
+}
+EXPORT_SYMBOL(misc_cg_uncharge);
+
+/**
+ * misc_cg_max_show() - Show misc cgroup max limit.
+ * @sf: Interface file
+ * @v: Arguments passed
+ *
+ * Context: Any context.
+ * Return: 0 to denote successful print.
+ */
+static int misc_cg_max_show(struct seq_file *sf, void *v)
+{
+	int i;
+	struct misc_cg *cg = css_misc(seq_css(sf));
+
+	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
+		if (misc_res_capacity[i]) {
+			if (cg->res[i].max == MAX_NUM)
+				seq_printf(sf, "%s max\n", misc_res_name[i]);
+			else
+				seq_printf(sf, "%s %u\n", misc_res_name[i],
+					   cg->res[i].max);
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * misc_cg_max_write() - Update the maximum limit of the cgroup.
+ * @of: Handler for the file.
+ * @buf: Data from the user. It should be either "max", 0, or a positive
+ *	 integer.
+ * @nbytes: Number of bytes of the data.
+ * @off: Offset in the file.
+ *
+ * User can pass data like:
+ * echo sev 23 > misc.max, OR
+ * echo sev max > misc.max
+ *
+ * Context: Any context.
+ * Return:
+ * * >= 0 - Number of bytes processed in the input.
+ * * -EINVAL - If buf is not valid.
+ * * -ERANGE - If number is bigger than unsigned int capacity.
+ */
+static ssize_t misc_cg_max_write(struct kernfs_open_file *of, char *buf,
+				 size_t nbytes, loff_t off)
+{
+	struct misc_cg *cg;
+	unsigned int max;
+	int ret = 0, i;
+	enum misc_res_type type = MISC_CG_RES_TYPES;
+	char *token;
+
+	buf = strstrip(buf);
+	token = strsep(&buf, " ");
+
+	if (!token || !buf)
+		return -EINVAL;
+
+	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
+		if (!strcmp(misc_res_name[i], token)) {
+			type = i;
+			break;
+		}
+	}
+
+	if (type == MISC_CG_RES_TYPES)
+		return -EINVAL;
+
+	if (!strcmp(MAX_STR, buf)) {
+		max = UINT_MAX;
+	} else {
+		ret = kstrtouint(buf, 0, &max);
+		if (ret)
+			return ret;
+	}
+
+	cg = css_misc(of_css(of));
+
+	if (misc_res_capacity[type])
+		cg->res[type].max = max;
+	else
+		ret = -EINVAL;
+
+	return ret ? ret : nbytes;
+}
+
+/**
+ * misc_cg_current_show() - Show current usage of the misc cgroup.
+ * @sf: Interface file
+ * @v: Arguments passed
+ *
+ * Context: Any context.
+ * Return: 0 to denote successful print.
+ */
+static int misc_cg_current_show(struct seq_file *sf, void *v)
+{
+	int i;
+	struct misc_cg *cg = css_misc(seq_css(sf));
+
+	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
+		if (misc_res_capacity[i])
+			seq_printf(sf, "%s %u\n", misc_res_name[i],
+				   atomic_read(&cg->res[i].usage));
+	}
+
+	return 0;
+}
+
+/**
+ * misc_cg_capacity_show() - Show the total capacity of misc res on the host.
+ * @sf: Interface file
+ * @v: Arguments passed
+ *
+ * Only present in the root cgroup directory.
+ *
+ * Context: Any context.
+ * Return: 0 to denote successful print.
+ */
+static int misc_cg_capacity_show(struct seq_file *sf, void *v)
+{
+	int i;
+	unsigned int cap;
+
+	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
+		cap = READ_ONCE(misc_res_capacity[i]);
+		if (cap)
+			seq_printf(sf, "%s %u\n", misc_res_name[i], cap);
+	}
+
+	return 0;
+}
+
+/* Misc cgroup interface files */
+static struct cftype misc_cg_files[] = {
+	{
+		.name = "max",
+		.write = misc_cg_max_write,
+		.seq_show = misc_cg_max_show,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "current",
+		.seq_show = misc_cg_current_show,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "capacity",
+		.seq_show = misc_cg_capacity_show,
+		.flags = CFTYPE_ONLY_ON_ROOT,
+	},
+	{}
+};
+
+/**
+ * misc_cg_alloc() - Allocate misc cgroup.
+ * @parent_css: Parent cgroup.
+ *
+ * Context: Process context.
+ * Return:
+ * * struct cgroup_subsys_state* - css of the allocated cgroup.
+ * * ERR_PTR(-ENOMEM) - No memory available to allocate.
+ */
+static struct cgroup_subsys_state *
+misc_cg_alloc(struct cgroup_subsys_state *parent_css)
+{
+	enum misc_res_type i;
+	struct misc_cg *cg;
+
+	if (!parent_css) {
+		cg = &root_cg;
+	} else {
+		cg = kzalloc(sizeof(*cg), GFP_KERNEL);
+		if (!cg)
+			return ERR_PTR(-ENOMEM);
+	}
+
+	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
+		cg->res[i].max = MAX_NUM;
+		atomic_set(&cg->res[i].usage, 0);
+	}
+
+	return &cg->css;
+}
+
+/**
+ * misc_cg_free() - Free the misc cgroup.
+ * @css: cgroup subsys object.
+ *
+ * Context: Any context.
+ */
+static void misc_cg_free(struct cgroup_subsys_state *css)
+{
+	kfree(css_misc(css));
+}
+
+/* Cgroup controller callbacks */
+struct cgroup_subsys misc_cgrp_subsys = {
+	.css_alloc = misc_cg_alloc,
+	.css_free = misc_cg_free,
+	.legacy_cftypes = misc_cg_files,
+	.dfl_cftypes = misc_cg_files,
+};
-- 
2.30.0.617.g56c4b15f3c-goog

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