[PATCH v4 16/18] x86/sgx: Limit process EPC usage with misc cgroup controller

Haitao Huang
2023-09-13T04:06:33Z

From: Kristen Carlson Accardi <kristen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>

Implement support for cgroup control of SGX Enclave Page Cache (EPC)
memory using the misc cgroup controller. EPC memory is independent
from normal system memory, e.g. must be reserved at boot from RAM and
cannot be converted between EPC and normal memory while the system is
running. EPC is managed by the SGX subsystem and is not accounted by
the memory controller.

Much like normal system memory, EPC memory can be overcommitted via
virtual memory techniques and pages can be swapped out of the EPC to
their backing store (normal system memory, e.g. shmem). The SGX EPC
subsystem is analogous to the memory subsystem and the SGX EPC controller
is in turn analogous to the memory controller; it implements limit and
protection models for EPC memory.

The misc controller provides a mechanism to set a hard limit of EPC
usage via the "sgx_epc" resource in "misc.max". The total EPC memory
available on the system is reported via the "sgx_epc" resource in
"misc.capacity".

This patch was modified from its original version to use the misc cgroup
controller instead of a custom controller.

Signed-off-by: Sean Christopherson <sean.j.christopherson-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Kristen Carlson Accardi <kristen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Signed-off-by: Haitao Huang <haitao.huang-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Tested-by: Mikko Ylinen <mikko.ylinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>

Cc: Sean Christopherson <seanjc-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
---
V4:
- Fix a white space issue in Kconfig (Randy).
- Update comments for LRU list as it can be owned by a cgroup.
- Fix comments for sgx_reclaim_epc_pages() and use IS_ENABLED consistently (Mikko)

V3:

1) Use the same maximum number of reclaiming candidate pages to be
processed, SGX_NR_TO_SCAN_MAX, for each reclaiming iteration in both
cgroup worker function and ksgxd. This fixes an overflow in the
backing store buffer with the same fixed size allocated on stack in
sgx_reclaim_epc_pages().

2) Initialize max for root EPC cgroup. Otherwise, all
misc_cg_try_charge() calls would fail as it checks for all limits of
ancestors all the way to the root node.

3) Start reclaiming whenever misc_cg_try_charge fails. Removed all
re-checks for limits and current usage. For all purposes and intent,
when misc_try_charge() fails, reclaiming is needed. This also corrects
an error of not reclaiming when the child limit is larger than one of
its ancestors.

4) Handle failure on charging to the root EPC cgroup. Failure on charging
to root means we are at or above capacity, so start reclaiming or return
OOM error.

5) Removed the custom cgroup tree walking iterator with epoch tracking
logic. Replaced it with just the plain css_for_each_descendant_pre
iterator. The custom iterator implemented a rather complex epoch scheme
I believe was intended to prevent extra reclaiming from multiple worker
threads doing the same walk but it turned out not matter much as each
thread would only reclaim when usage is above limit. Using the plain
css_for_each_descendant_pre iterator simplified code a bit.

6) Do not reclaim synchronously in misc_max_write callback which would
block the user. Instead queue an async work item to run the reclaiming
loop.

7) Other minor refactoring:
- Remove unused params in epc_cgroup APIs
- centralize uncharge into sgx_free_epc_page()
---
arch/x86/Kconfig | 13 +
arch/x86/kernel/cpu/sgx/Makefile | 1 +
arch/x86/kernel/cpu/sgx/epc_cgroup.c | 406 +++++++++++++++++++++++++++
arch/x86/kernel/cpu/sgx/epc_cgroup.h | 59 ++++
arch/x86/kernel/cpu/sgx/main.c | 67 ++++-
arch/x86/kernel/cpu/sgx/sgx.h | 17 +-
6 files changed, 547 insertions(+), 16 deletions(-)
create mode 100644 arch/x86/kernel/cpu/sgx/epc_cgroup.c
create mode 100644 arch/x86/kernel/cpu/sgx/epc_cgroup.h

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 982b777eadc7..55fcf182d4a3 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1921,6 +1921,19 @@ config X86_SGX

If unsure, say N.

+config CGROUP_SGX_EPC
+ bool "Miscellaneous Cgroup Controller for Enclave Page Cache (EPC) for Intel SGX"
+ depends on X86_SGX && CGROUP_MISC
+ help
+ Provides control over the EPC footprint of tasks in a cgroup via
+ the Miscellaneous cgroup controller.
+
+ EPC is a subset of regular memory that is usable only by SGX
+ enclaves and is very limited in quantity, e.g. less than 1%
+ of total DRAM.
+
+ Say N if unsure.
+
config X86_USER_SHADOW_STACK
bool "X86 userspace shadow stack"
depends on AS_WRUSS
diff --git a/arch/x86/kernel/cpu/sgx/Makefile b/arch/x86/kernel/cpu/sgx/Makefile
index 9c1656779b2a..12901a488da7 100644
--- a/arch/x86/kernel/cpu/sgx/Makefile
+++ b/arch/x86/kernel/cpu/sgx/Makefile
@@ -4,3 +4,4 @@ obj-y += \
ioctl.o \
main.o
obj-$(CONFIG_X86_SGX_KVM) += virt.o
+obj-$(CONFIG_CGROUP_SGX_EPC) += epc_cgroup.o
diff --git a/arch/x86/kernel/cpu/sgx/epc_cgroup.c b/arch/x86/kernel/cpu/sgx/epc_cgroup.c
new file mode 100644
index 000000000000..7b86eb074abe
--- /dev/null
+++ b/arch/x86/kernel/cpu/sgx/epc_cgroup.c
@@ -0,0 +1,406 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright(c) 2022 Intel Corporation.
+
+#include <linux/atomic.h>
+#include <linux/kernel.h>
+#include <linux/ratelimit.h>
+#include <linux/sched/signal.h>
+#include <linux/slab.h>
+#include <linux/threads.h>
+
+#include "epc_cgroup.h"
+
+#define SGX_EPC_RECLAIM_MIN_PAGES 16UL
+#define SGX_EPC_RECLAIM_IGNORE_AGE_THRESHOLD 5
+#define SGX_EPC_RECLAIM_OOM_THRESHOLD 5
+
+static struct workqueue_struct *sgx_epc_cg_wq;
+static bool sgx_epc_cgroup_oom(struct sgx_epc_cgroup *root);
+
+struct sgx_epc_reclaim_control {
+ struct sgx_epc_cgroup *epc_cg;
+ int nr_fails;
+ bool ignore_age;
+};
+
+static inline u64 sgx_epc_cgroup_page_counter_read(struct sgx_epc_cgroup *epc_cg)
+{
+ return atomic64_read(&epc_cg->cg->res[MISC_CG_RES_SGX_EPC].usage) / PAGE_SIZE;
+}
+
+static inline u64 sgx_epc_cgroup_max_pages(struct sgx_epc_cgroup *epc_cg)
+{
+ return READ_ONCE(epc_cg->cg->res[MISC_CG_RES_SGX_EPC].max) / PAGE_SIZE;
+}
+
+static inline u64 sgx_epc_cgroup_max_pages_to_root(struct sgx_epc_cgroup *epc_cg)
+{
+ struct misc_cg *i = epc_cg->cg;
+ u64 m = U64_MAX;
+
+ while (i) {
+ m = min(m, READ_ONCE(i->res[MISC_CG_RES_SGX_EPC].max));
+ i = misc_cg_parent(i);
+ }
+ return m / PAGE_SIZE;
+}
+
+static inline struct sgx_epc_cgroup *sgx_epc_cgroup_from_misc_cg(struct misc_cg *cg)
+{
+ if (cg)
+ return (struct sgx_epc_cgroup *)(cg->res[MISC_CG_RES_SGX_EPC].priv);
+
+ return NULL;
+}
+
+static inline bool sgx_epc_cgroup_disabled(void)
+{
+ return !cgroup_subsys_enabled(misc_cgrp_subsys);
+}
+
+/**
+ * sgx_epc_cgroup_lru_empty - check if a cgroup tree has no pages on its lrus
+ * @root: root of the tree to check
+ *
+ * Return: %true if all cgroups under the specified root have empty LRU lists.
+ * Used to avoid livelocks due to a cgroup having a non-zero charge count but
+ * no pages on its LRUs, e.g. due to a dead enclave waiting to be released or
+ * because all pages in the cgroup are unreclaimable.
+ */
+bool sgx_epc_cgroup_lru_empty(struct sgx_epc_cgroup *root)
+{
+ struct cgroup_subsys_state *css_root = NULL;
+ struct cgroup_subsys_state *pos = NULL;
+ struct sgx_epc_cgroup *epc_cg = NULL;
+ bool ret = true;
+
+ /*
+ * Caller ensure css_root ref acquired
+ */
+ css_root = root ? &root->cg->css : &(misc_cg_root()->css);
+
+ rcu_read_lock();
+ css_for_each_descendant_pre(pos, css_root) {
+ if (!css_tryget(pos))
+ break;
+
+ rcu_read_unlock();
+
+ epc_cg = sgx_epc_cgroup_from_misc_cg(css_misc(pos));
+
+ spin_lock(&epc_cg->lru.lock);
+ ret = list_empty(&epc_cg->lru.reclaimable);
+ spin_unlock(&epc_cg->lru.lock);
+
+ rcu_read_lock();
+ css_put(pos);
+ if (!ret)
+ break;
+ }
+ rcu_read_unlock();
+ return ret;
+}
+
+/**
+ * sgx_epc_cgroup_isolate_pages - walk a cgroup tree and separate pages
+ * @root: root of the tree to start walking
+ * @nr_to_scan: The number of pages that need to be isolated
+ * @dst: Destination list to hold the isolated pages
+ *
+ * Walk the cgroup tree and isolate the pages in the hierarchy
+ * for reclaiming.
+ */
+void sgx_epc_cgroup_isolate_pages(struct sgx_epc_cgroup *root,
+ size_t *nr_to_scan, struct list_head *dst)
+{
+ struct cgroup_subsys_state *css_root = NULL;
+ struct cgroup_subsys_state *pos = NULL;
+ struct sgx_epc_cgroup *epc_cg = NULL;
+
+ if (!*nr_to_scan)
+ return;
+
+ /* Caller ensure css_root ref acquired */
+ css_root = root ? &root->cg->css : &(misc_cg_root()->css);
+
+ rcu_read_lock();
+ css_for_each_descendant_pre(pos, css_root) {
+ if (!css_tryget(pos))
+ break;
+ rcu_read_unlock();
+
+ epc_cg = sgx_epc_cgroup_from_misc_cg(css_misc(pos));
+ sgx_isolate_epc_pages(&epc_cg->lru, nr_to_scan, dst);
+
+ rcu_read_lock();
+ css_put(pos);
+ if (!*nr_to_scan)
+ break;
+ }
+ rcu_read_unlock();
+}
+
+static int sgx_epc_cgroup_reclaim_pages(unsigned long nr_pages,
+ struct sgx_epc_reclaim_control *rc)
+{
+ /*
+ * Ensure sgx_reclaim_pages is called with a minimum and maximum
+ * number of pages. Attempting to reclaim only a few pages will
+ * often fail and is inefficient, while reclaiming a huge number
+ * of pages can result in soft lockups due to holding various
+ * locks for an extended duration.
+ */
+ nr_pages = max(nr_pages, SGX_EPC_RECLAIM_MIN_PAGES);
+ nr_pages = min(nr_pages, SGX_NR_TO_SCAN_MAX);
+
+ return sgx_reclaim_epc_pages(nr_pages, rc->ignore_age, rc->epc_cg);
+}
+
+static int sgx_epc_cgroup_reclaim_failed(struct sgx_epc_reclaim_control *rc)
+{
+ if (sgx_epc_cgroup_lru_empty(rc->epc_cg))
+ return -ENOMEM;
+
+ ++rc->nr_fails;
+ if (rc->nr_fails > SGX_EPC_RECLAIM_IGNORE_AGE_THRESHOLD)
+ rc->ignore_age = true;
+
+ return 0;
+}
+
+static inline
+void sgx_epc_reclaim_control_init(struct sgx_epc_reclaim_control *rc,
+ struct sgx_epc_cgroup *epc_cg)
+{
+ rc->epc_cg = epc_cg;
+ rc->nr_fails = 0;
+ rc->ignore_age = false;
+}
+
+/*
+ * Scheduled by sgx_epc_cgroup_try_charge() to reclaim pages from the
+ * cgroup when the cgroup is at/near its maximum capacity
+ */
+static void sgx_epc_cgroup_reclaim_work_func(struct work_struct *work)
+{
+ struct sgx_epc_reclaim_control rc;
+ struct sgx_epc_cgroup *epc_cg;
+ u64 cur, max;
+
+ epc_cg = container_of(work, struct sgx_epc_cgroup, reclaim_work);
+
+ sgx_epc_reclaim_control_init(&rc, epc_cg);
+
+ for (;;) {
+ max = sgx_epc_cgroup_max_pages_to_root(epc_cg);
+
+ /*
+ * Adjust the limit down by one page, the goal is to free up
+ * pages for fault allocations, not to simply obey the limit.
+ * Conditionally decrementing max also means the cur vs. max
+ * check will correctly handle the case where both are zero.
+ */
+ if (max)
+ max--;
+
+ /*
+ * Unless the limit is extremely low, in which case forcing
+ * reclaim will likely cause thrashing, force the cgroup to
+ * reclaim at least once if it's operating *near* its maximum
+ * limit by adjusting @max down by half the min reclaim size.
+ * This work func is scheduled by sgx_epc_cgroup_try_charge
+ * when it cannot directly reclaim due to being in an atomic
+ * context, e.g. EPC allocation in a fault handler. Waiting
+ * to reclaim until the cgroup is actually at its limit is less
+ * performant as it means the faulting task is effectively
+ * blocked until a worker makes its way through the global work
+ * queue.
+ */
+ if (max > SGX_NR_TO_SCAN_MAX)
+ max -= (SGX_EPC_RECLAIM_MIN_PAGES / 2);
+
+ max = min(max, sgx_epc_total_pages);
+ cur = sgx_epc_cgroup_page_counter_read(epc_cg);
+ if (cur <= max)
+ break;
+ /* Nothing reclaimable */
+ if (sgx_epc_cgroup_lru_empty(epc_cg)) {
+ if (!sgx_epc_cgroup_oom(epc_cg))
+ break;
+
+ continue;
+ }
+
+ if (!sgx_epc_cgroup_reclaim_pages(cur - max, &rc)) {
+ if (sgx_epc_cgroup_reclaim_failed(&rc))
+ break;
+ }
+ }
+}
+
+static int __sgx_epc_cgroup_try_charge(struct sgx_epc_cgroup *epc_cg,
+ bool reclaim)
+{
+ struct sgx_epc_reclaim_control rc;
+ unsigned int nr_empty = 0;
+
+ sgx_epc_reclaim_control_init(&rc, epc_cg);
+
+ for (;;) {
+ if (!misc_cg_try_charge(MISC_CG_RES_SGX_EPC, epc_cg->cg,
+ PAGE_SIZE))
+ break;
+
+ if (sgx_epc_cgroup_lru_empty(epc_cg))
+ return -ENOMEM;
+
+ if (signal_pending(current))
+ return -ERESTARTSYS;
+
+ if (!reclaim) {
+ queue_work(sgx_epc_cg_wq, &rc.epc_cg->reclaim_work);
+ return -EBUSY;
+ }
+
+ if (!sgx_epc_cgroup_reclaim_pages(1, &rc)) {
+ if (sgx_epc_cgroup_reclaim_failed(&rc)) {
+ if (++nr_empty > SGX_EPC_RECLAIM_OOM_THRESHOLD)
+ return -ENOMEM;
+ schedule();
+ }
+ }
+ }
+ if (epc_cg->cg != misc_cg_root())
+ css_get(&epc_cg->cg->css);
+
+ return 0;
+}
+
+/**
+ * sgx_epc_cgroup_try_charge - hierarchically try to charge a single EPC page
+ * @mm: the mm_struct of the process to charge
+ * @reclaim: whether or not synchronous reclaim is allowed
+ *
+ * Returns EPC cgroup or NULL on success, -errno on failure.
+ */
+struct sgx_epc_cgroup *sgx_epc_cgroup_try_charge(bool reclaim)
+{
+ struct sgx_epc_cgroup *epc_cg;
+ int ret;
+
+ if (sgx_epc_cgroup_disabled())
+ return NULL;
+
+ epc_cg = sgx_epc_cgroup_from_misc_cg(get_current_misc_cg());
+ ret = __sgx_epc_cgroup_try_charge(epc_cg, reclaim);
+ put_misc_cg(epc_cg->cg);
+
+ if (ret)
+ return ERR_PTR(ret);
+
+ return epc_cg;
+}
+
+/**
+ * sgx_epc_cgroup_uncharge - hierarchically uncharge EPC pages
+ * @epc_cg: the charged epc cgroup
+ */
+void sgx_epc_cgroup_uncharge(struct sgx_epc_cgroup *epc_cg)
+{
+ if (sgx_epc_cgroup_disabled())
+ return;
+
+ misc_cg_uncharge(MISC_CG_RES_SGX_EPC, epc_cg->cg, PAGE_SIZE);
+
+ if (epc_cg->cg != misc_cg_root())
+ put_misc_cg(epc_cg->cg);
+}
+
+static bool sgx_epc_cgroup_oom(struct sgx_epc_cgroup *root)
+{
+ struct cgroup_subsys_state *css_root = NULL;
+ struct cgroup_subsys_state *pos = NULL;
+ struct sgx_epc_cgroup *epc_cg = NULL;
+ bool oom = false;
+
+ /* Caller ensure css_root ref acquired */
+ css_root = root ? &root->cg->css : &(misc_cg_root()->css);
+
+ rcu_read_lock();
+ css_for_each_descendant_pre(pos, css_root) {
+ /* skip dead ones */
+ if (!css_tryget(pos))
+ continue;
+
+ rcu_read_unlock();
+
+ epc_cg = sgx_epc_cgroup_from_misc_cg(css_misc(pos));
+ oom = sgx_epc_oom(&epc_cg->lru);
+
+ rcu_read_lock();
+ css_put(pos);
+ if (oom)
+ break;
+ }
+ rcu_read_unlock();
+ return oom;
+}
+
+static void sgx_epc_cgroup_free(struct misc_cg *cg)
+{
+ struct sgx_epc_cgroup *epc_cg;
+
+ epc_cg = sgx_epc_cgroup_from_misc_cg(cg);
+ cancel_work_sync(&epc_cg->reclaim_work);
+ kfree(epc_cg);
+}
+
+static void sgx_epc_cgroup_max_write(struct misc_cg *cg)
+{
+ struct sgx_epc_reclaim_control rc;
+ struct sgx_epc_cgroup *epc_cg;
+
+ epc_cg = sgx_epc_cgroup_from_misc_cg(cg);
+
+ sgx_epc_reclaim_control_init(&rc, epc_cg);
+ /* Let the reclaimer to do the work so user is not blocked */
+ queue_work(sgx_epc_cg_wq, &rc.epc_cg->reclaim_work);
+}
+
+static int sgx_epc_cgroup_alloc(struct misc_cg *cg)
+{
+ struct sgx_epc_cgroup *epc_cg;
+
+ epc_cg = kzalloc(sizeof(*epc_cg), GFP_KERNEL);
+ if (!epc_cg)
+ return -ENOMEM;
+
+ sgx_lru_init(&epc_cg->lru);
+ INIT_WORK(&epc_cg->reclaim_work, sgx_epc_cgroup_reclaim_work_func);
+ cg->res[MISC_CG_RES_SGX_EPC].misc_cg_alloc = sgx_epc_cgroup_alloc;
+ cg->res[MISC_CG_RES_SGX_EPC].misc_cg_free = sgx_epc_cgroup_free;
+ cg->res[MISC_CG_RES_SGX_EPC].misc_cg_max_write = sgx_epc_cgroup_max_write;
+ cg->res[MISC_CG_RES_SGX_EPC].priv = epc_cg;
+ epc_cg->cg = cg;
+ return 0;
+}
+
+static int __init sgx_epc_cgroup_init(void)
+{
+ struct misc_cg *cg;
+
+ if (!boot_cpu_has(X86_FEATURE_SGX))
+ return 0;
+
+ sgx_epc_cg_wq = alloc_workqueue("sgx_epc_cg_wq",
+ WQ_UNBOUND | WQ_FREEZABLE,
+ WQ_UNBOUND_MAX_ACTIVE);
+ BUG_ON(!sgx_epc_cg_wq);
+
+ cg = misc_cg_root();
+ BUG_ON(!cg);
+ WRITE_ONCE(cg->res[MISC_CG_RES_SGX_EPC].max, U64_MAX);
+ atomic64_set(&cg->res[MISC_CG_RES_SGX_EPC].usage, 0UL);
+ return sgx_epc_cgroup_alloc(cg);
+}
+subsys_initcall(sgx_epc_cgroup_init);
diff --git a/arch/x86/kernel/cpu/sgx/epc_cgroup.h b/arch/x86/kernel/cpu/sgx/epc_cgroup.h
new file mode 100644
index 000000000000..dfc902f4d96f
--- /dev/null
+++ b/arch/x86/kernel/cpu/sgx/epc_cgroup.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright(c) 2022 Intel Corporation. */
+#ifndef _INTEL_SGX_EPC_CGROUP_H_
+#define _INTEL_SGX_EPC_CGROUP_H_
+
+#include <asm/sgx.h>
+#include <linux/cgroup.h>
+#include <linux/list.h>
+#include <linux/misc_cgroup.h>
+#include <linux/page_counter.h>
+#include <linux/workqueue.h>
+
+#include "sgx.h"
+
+#ifndef CONFIG_CGROUP_SGX_EPC
+#define MISC_CG_RES_SGX_EPC MISC_CG_RES_TYPES
+struct sgx_epc_cgroup;
+
+static inline struct sgx_epc_cgroup *sgx_epc_cgroup_try_charge(bool reclaim)
+{
+ return NULL;
+}
+
+static inline void sgx_epc_cgroup_uncharge(struct sgx_epc_cgroup *epc_cg) { }
+
+static inline void sgx_epc_cgroup_isolate_pages(struct sgx_epc_cgroup *root,
+ size_t *nr_to_scan,
+ struct list_head *dst) { }
+
+static inline struct sgx_epc_lru_lists *epc_cg_lru(struct sgx_epc_cgroup *epc_cg)
+{
+ return NULL;
+}
+
+static bool sgx_epc_cgroup_lru_empty(struct sgx_epc_cgroup *root)
+{
+ return true;
+}
+#else
+struct sgx_epc_cgroup {
+ struct misc_cg *cg;
+ struct sgx_epc_lru_lists lru;
+ struct work_struct reclaim_work;
+};
+
+struct sgx_epc_cgroup *sgx_epc_cgroup_try_charge(bool reclaim);
+void sgx_epc_cgroup_uncharge(struct sgx_epc_cgroup *epc_cg);
+bool sgx_epc_cgroup_lru_empty(struct sgx_epc_cgroup *root);
+void sgx_epc_cgroup_isolate_pages(struct sgx_epc_cgroup *root,
+ size_t *nr_to_scan, struct list_head *dst);
+static inline struct sgx_epc_lru_lists *epc_cg_lru(struct sgx_epc_cgroup *epc_cg)
+{
+ if (epc_cg)
+ return &epc_cg->lru;
+ return NULL;
+}
+#endif
+
+#endif /* _INTEL_SGX_EPC_CGROUP_H_ */
diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 3d396fe5ec09..20de17f4f576 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -6,6 +6,7 @@
#include <linux/highmem.h>
#include <linux/kthread.h>
#include <linux/miscdevice.h>
+#include <linux/misc_cgroup.h>
#include <linux/node.h>
#include <linux/pagemap.h>
#include <linux/ratelimit.h>
@@ -17,11 +18,9 @@
#include "driver.h"
#include "encl.h"
#include "encls.h"
-/**
- * Maximum number of pages to scan for reclaiming.
- */
-#define SGX_NR_TO_SCAN_MAX 32
+#include "epc_cgroup.h"

+u64 sgx_epc_total_pages;
struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];
static int sgx_nr_epc_sections;
static struct task_struct *ksgxd_tsk;
@@ -36,11 +35,17 @@ static struct sgx_epc_lru_lists sgx_global_lru;

static inline struct sgx_epc_lru_lists *sgx_lru_lists(struct sgx_epc_page *epc_page)
{
+ if (IS_ENABLED(CONFIG_CGROUP_SGX_EPC))
+ return epc_cg_lru(epc_page->epc_cg);
+
return &sgx_global_lru;
}

static inline bool sgx_can_reclaim(void)
{
+ if (IS_ENABLED(CONFIG_CGROUP_SGX_EPC))
+ return !sgx_epc_cgroup_lru_empty(NULL);
+
return !list_empty(&sgx_global_lru.reclaimable);
}

@@ -299,14 +304,14 @@ static void sgx_reclaimer_write(struct sgx_epc_page *epc_page,
* @nr_to_scan: Number of pages to scan for reclaim
* @dst: Destination list to hold the isolated pages
*/
-void sgx_isolate_epc_pages(struct sgx_epc_lru_lists *lru, size_t nr_to_scan,
+void sgx_isolate_epc_pages(struct sgx_epc_lru_lists *lru, size_t *nr_to_scan,
struct list_head *dst)
{
struct sgx_encl_page *encl_page;
struct sgx_epc_page *epc_page;

spin_lock(&lru->lock);
- for (; nr_to_scan > 0; --nr_to_scan) {
+ for (; *nr_to_scan > 0; --(*nr_to_scan)) {
epc_page = list_first_entry_or_null(&lru->reclaimable, struct sgx_epc_page, list);
if (!epc_page)
break;
@@ -331,6 +336,7 @@ void sgx_isolate_epc_pages(struct sgx_epc_lru_lists *lru, size_t nr_to_scan,
* sgx_reclaim_epc_pages() - Reclaim EPC pages from the consumers
* @nr_to_scan: Number of EPC pages to scan for reclaim
* @ignore_age: Reclaim a page even if it is young
+ * @epc_cg: EPC cgroup from which to reclaim
*
* Take a fixed number of pages from the head of the active page pool and
* reclaim them to the enclave's private shmem files. Skip the pages, which have
@@ -344,7 +350,8 @@ void sgx_isolate_epc_pages(struct sgx_epc_lru_lists *lru, size_t nr_to_scan,
* problematic as it would increase the lock contention too much, which would
* halt forward progress.
*/
-size_t sgx_reclaim_epc_pages(size_t nr_to_scan, bool ignore_age)
+size_t sgx_reclaim_epc_pages(size_t nr_to_scan, bool ignore_age,
+ struct sgx_epc_cgroup *epc_cg)
{
struct sgx_backing backing[SGX_NR_TO_SCAN_MAX];
struct sgx_epc_page *epc_page, *tmp;
@@ -355,7 +362,15 @@ size_t sgx_reclaim_epc_pages(size_t nr_to_scan, bool ignore_age)
size_t ret;
size_t i;

- sgx_isolate_epc_pages(&sgx_global_lru, nr_to_scan, &iso);
+ /*
+ * If a specific cgroup is not being targeted, take from the global
+ * list first, even when cgroups are enabled. If there are
+ * pages on the global LRU then they should get reclaimed asap.
+ */
+ if (!IS_ENABLED(CONFIG_CGROUP_SGX_EPC) || !epc_cg)
+ sgx_isolate_epc_pages(&sgx_global_lru, &nr_to_scan, &iso);
+
+ sgx_epc_cgroup_isolate_pages(epc_cg, &nr_to_scan, &iso);

if (list_empty(&iso))
return 0;
@@ -422,7 +437,7 @@ static bool sgx_should_reclaim(unsigned long watermark)
void sgx_reclaim_direct(void)
{
if (sgx_should_reclaim(SGX_NR_LOW_PAGES))
- sgx_reclaim_epc_pages(SGX_NR_TO_SCAN, false);
+ sgx_reclaim_epc_pages(SGX_NR_TO_SCAN, false, NULL);
}

static int ksgxd(void *p)
@@ -445,7 +460,7 @@ static int ksgxd(void *p)
sgx_should_reclaim(SGX_NR_HIGH_PAGES));

if (sgx_should_reclaim(SGX_NR_HIGH_PAGES))
- sgx_reclaim_epc_pages(SGX_NR_TO_SCAN, false);
+ sgx_reclaim_epc_pages(SGX_NR_TO_SCAN, false, NULL);

cond_resched();
}
@@ -599,6 +614,11 @@ int sgx_drop_epc_page(struct sgx_epc_page *page)
struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim)
{
struct sgx_epc_page *page;
+ struct sgx_epc_cgroup *epc_cg;
+
+ epc_cg = sgx_epc_cgroup_try_charge(reclaim);
+ if (IS_ERR(epc_cg))
+ return ERR_CAST(epc_cg);

for ( ; ; ) {
page = __sgx_alloc_epc_page();
@@ -607,8 +627,10 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim)
break;
}

- if (!sgx_can_reclaim())
- return ERR_PTR(-ENOMEM);
+ if (!sgx_can_reclaim()) {
+ page = ERR_PTR(-ENOMEM);
+ break;
+ }

if (!reclaim) {
page = ERR_PTR(-EBUSY);
@@ -620,10 +642,17 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim)
break;
}

- sgx_reclaim_epc_pages(SGX_NR_TO_SCAN, false);
+ sgx_reclaim_epc_pages(SGX_NR_TO_SCAN, false, NULL);
cond_resched();
}

+ if (!IS_ERR(page)) {
+ WARN_ON_ONCE(page->epc_cg);
+ page->epc_cg = epc_cg;
+ } else {
+ sgx_epc_cgroup_uncharge(epc_cg);
+ }
+
if (sgx_should_reclaim(SGX_NR_LOW_PAGES))
wake_up(&ksgxd_waitq);

@@ -646,6 +675,11 @@ void sgx_free_epc_page(struct sgx_epc_page *page)

WARN_ON_ONCE(page->flags & (SGX_EPC_PAGE_STATE_MASK));

+ if (page->epc_cg) {
+ sgx_epc_cgroup_uncharge(page->epc_cg);
+ page->epc_cg = NULL;
+ }
+
spin_lock(&node->lock);

page->encl_page = NULL;
@@ -656,6 +690,7 @@ void sgx_free_epc_page(struct sgx_epc_page *page)
page->flags = SGX_EPC_PAGE_FREE;

spin_unlock(&node->lock);
+
atomic_long_inc(&sgx_nr_free_pages);
}

@@ -825,6 +860,7 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
section->pages[i].flags = 0;
section->pages[i].encl_page = NULL;
section->pages[i].poison = 0;
+ section->pages[i].epc_cg = NULL;
list_add_tail(&section->pages[i].list, &sgx_dirty_page_list);
}

@@ -969,6 +1005,7 @@ static void __init arch_update_sysfs_visibility(int nid) {}
static bool __init sgx_page_cache_init(void)
{
u32 eax, ebx, ecx, edx, type;
+ u64 capacity = 0;
u64 pa, size;
int nid;
int i;
@@ -1019,6 +1056,7 @@ static bool __init sgx_page_cache_init(void)

sgx_epc_sections[i].node = &sgx_numa_nodes[nid];
sgx_numa_nodes[nid].size += size;
+ capacity += size;

sgx_nr_epc_sections++;
}
@@ -1028,6 +1066,9 @@ static bool __init sgx_page_cache_init(void)
return false;
}

+ misc_cg_set_capacity(MISC_CG_RES_SGX_EPC, capacity);
+ sgx_epc_total_pages = capacity >> PAGE_SHIFT;
+
return true;
}

diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index 7e21192b87a8..bf746d2af96d 100644
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -19,6 +19,11 @@

#define SGX_MAX_EPC_SECTIONS 8
#define SGX_EEXTEND_BLOCK_SIZE 256
+
+/*
+ * Maximum number of pages to scan for reclaiming.
+ */
+#define SGX_NR_TO_SCAN_MAX 32UL
#define SGX_NR_TO_SCAN 16
#define SGX_NR_LOW_PAGES 32
#define SGX_NR_HIGH_PAGES 64
@@ -70,6 +75,8 @@ enum sgx_epc_page_state {
/* flag for pages owned by a sgx_encl struct */
#define SGX_EPC_OWNER_ENCL BIT(4)

+struct sgx_epc_cgroup;
+
struct sgx_epc_page {
unsigned int section;
u16 flags;
@@ -79,6 +86,7 @@ struct sgx_epc_page {
struct sgx_encl *encl;
};
struct list_head list;
+ struct sgx_epc_cgroup *epc_cg;
};

static inline void sgx_epc_page_reset_state(struct sgx_epc_page *page)
@@ -127,6 +135,7 @@ struct sgx_epc_section {
struct sgx_numa_node *node;
};

+extern u64 sgx_epc_total_pages;
extern struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];

static inline unsigned long sgx_get_epc_phys_addr(struct sgx_epc_page *page)
@@ -150,7 +159,8 @@ static inline void *sgx_get_epc_virt_addr(struct sgx_epc_page *page)
}

/*
- * Contains EPC pages tracked by the reclaimer (ksgxd).
+ * Contains EPC pages tracked by the global reclaimer (ksgxd) or an EPC
+ * cgroup.
*/
struct sgx_epc_lru_lists {
spinlock_t lock;
@@ -177,8 +187,9 @@ void sgx_record_epc_page(struct sgx_epc_page *page, unsigned long flags);
int sgx_drop_epc_page(struct sgx_epc_page *page);
struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim);
bool sgx_epc_oom(struct sgx_epc_lru_lists *lrus);
-size_t sgx_reclaim_epc_pages(size_t nr_to_scan, bool ignore_age);
-void sgx_isolate_epc_pages(struct sgx_epc_lru_lists *lrus, size_t nr_to_scan,
+size_t sgx_reclaim_epc_pages(size_t nr_to_scan, bool ignore_age,
+ struct sgx_epc_cgroup *epc_cg);
+void sgx_isolate_epc_pages(struct sgx_epc_lru_lists *lrus, size_t *nr_to_scan,
struct list_head *dst);

void sgx_ipi_cb(void *info);
--
2.25.1