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Subject: [RFC 1/2] cgroup: sev: Add misc cgroup controller
From:   Vipin Sharma <vipinsh@google.com>
To:     tj@kernel.org, thomas.lendacky@amd.com, brijesh.singh@amd.com,
        jon.grimm@amd.com, eric.vantassell@amd.com, pbonzini@redhat.com,
        hannes@cmpxchg.org, frankja@linux.ibm.com, borntraeger@de.ibm.com
Cc:     corbet@lwn.net, seanjc@google.com, vkuznets@redhat.com,
        wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com,
        gingell@google.com, rientjes@google.com, dionnaglaze@google.com,
        kvm@vger.kernel.org, x86@kernel.org, cgroups@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        Vipin Sharma <vipinsh@google.com>
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Precedence: bulk

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@google.com>
Reviewed-by: David Rientjes <rientjes@google.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@google.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@google.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