[PATCH v10 12/14] x86/sgx: Turn on per-cgroup EPC reclamation

[Haitao Huang <haitao.huang@linux.intel.com>]

From: Kristen Carlson Accardi <kristen@linux.intel.com>

Previous patches have implemented all infrastructure needed for
per-cgroup EPC page tracking and reclaiming. But all reclaimable EPC
pages are still tracked in the global LRU as sgx_lru_list() returns hard
coded reference to the global LRU.

Change sgx_lru_list() to return the LRU of the cgroup in which the given
EPC page is allocated.

This makes all EPC pages tracked in per-cgroup LRUs and the global
reclaimer (ksgxd) will not be able to reclaim any pages from the global
LRU. However, in cases of over-committing, i.e., the sum of cgroup
limits greater than the total capacity, cgroups may never reclaim but
the total usage can still be near the capacity. Therefore a global
reclamation is still needed in those cases and it should be performed
from the root cgroup.

Modify sgx_reclaim_pages_global(), to reclaim from the root EPC cgroup
when cgroup is enabled, otherwise from the global LRU. Export
sgx_cgroup_reclaim_pages() in the header file so it can be reused for
this purpose.

Similarly, modify sgx_can_reclaim(), to check emptiness of LRUs of all
cgroups when EPC cgroup is enabled, otherwise only check the global LRU.
Export sgx_cgroup_lru_empty() so it can be reused for this purpose.

Finally, change sgx_reclaim_direct(), to check and ensure there are free
pages at cgroup level so forward progress can be made by the caller.
Export sgx_cgroup_should_reclaim() for reuse.

With these changes, the global reclamation and per-cgroup reclamation
both work properly with all pages tracked in per-cgroup LRUs.

Co-developed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Co-developed-by: Haitao Huang <haitao.huang@linux.intel.com>
Signed-off-by: Haitao Huang <haitao.huang@linux.intel.com>
---
V10:
- Add comment to clarify each page belongs to one cgroup, or the root by
default. (Kai)
- Merge the changes that expose sgx_cgroup_* functions to this patch.
- Add changes for sgx_reclaim_direct() that was missed previously.

V7:
- Split this out from the big patch, #10 in V6. (Dave, Kai)
---
 arch/x86/kernel/cpu/sgx/epc_cgroup.c |  6 +++---
 arch/x86/kernel/cpu/sgx/epc_cgroup.h |  7 +++++++
 arch/x86/kernel/cpu/sgx/main.c       | 29 +++++++++++++++++++++++++++-
 3 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/epc_cgroup.c b/arch/x86/kernel/cpu/sgx/epc_cgroup.c
index 1defbf213e8d..cacd9e93344e 100644
--- a/arch/x86/kernel/cpu/sgx/epc_cgroup.c
+++ b/arch/x86/kernel/cpu/sgx/epc_cgroup.c
@@ -72,7 +72,7 @@ static inline u64 sgx_cgroup_max_pages_to_root(struct sgx_cgroup *sgx_cg)
  *
  * Return: %true if all cgroups under the specified root have empty LRU lists.
  */
-static bool sgx_cgroup_lru_empty(struct misc_cg *root)
+bool sgx_cgroup_lru_empty(struct misc_cg *root)
 {
 	struct cgroup_subsys_state *css_root;
 	struct cgroup_subsys_state *pos;
@@ -125,7 +125,7 @@ static bool sgx_cgroup_lru_empty(struct misc_cg *root)
  * triggering reclamation, and call cond_resched() in between iterations to
  * avoid indefinite blocking.
  */
-static void sgx_cgroup_reclaim_pages(struct misc_cg *root, struct mm_struct *charge_mm)
+void sgx_cgroup_reclaim_pages(struct misc_cg *root, struct mm_struct *charge_mm)
 {
 	struct cgroup_subsys_state *css_root;
 	struct cgroup_subsys_state *pos;
@@ -166,7 +166,7 @@ static void sgx_cgroup_reclaim_pages(struct misc_cg *root, struct mm_struct *cha
  * threshold (%SGX_CG_MIN_FREE_PAGE) and there are reclaimable pages within the
  * cgroup.
  */
-static bool sgx_cgroup_should_reclaim(struct sgx_cgroup *sgx_cg)
+bool sgx_cgroup_should_reclaim(struct sgx_cgroup *sgx_cg)
 {
 	u64 cur, max;
 
diff --git a/arch/x86/kernel/cpu/sgx/epc_cgroup.h b/arch/x86/kernel/cpu/sgx/epc_cgroup.h
index f66570d3ef42..8f55b38157da 100644
--- a/arch/x86/kernel/cpu/sgx/epc_cgroup.h
+++ b/arch/x86/kernel/cpu/sgx/epc_cgroup.h
@@ -28,6 +28,10 @@ static inline int sgx_cgroup_try_charge(struct sgx_cgroup *sgx_cg, enum sgx_recl
 static inline void sgx_cgroup_uncharge(struct sgx_cgroup *sgx_cg) { }
 
 static inline void sgx_cgroup_init(void) { }
+
+static inline void sgx_cgroup_reclaim_pages(struct misc_cg *root, struct mm_struct *charge_mm)
+{
+}
 #else
 struct sgx_cgroup {
 	struct misc_cg *cg;
@@ -65,6 +69,9 @@ static inline void sgx_put_cg(struct sgx_cgroup *sgx_cg)
 
 int sgx_cgroup_try_charge(struct sgx_cgroup *sgx_cg, enum sgx_reclaim reclaim);
 void sgx_cgroup_uncharge(struct sgx_cgroup *sgx_cg);
+bool sgx_cgroup_lru_empty(struct misc_cg *root);
+bool sgx_cgroup_should_reclaim(struct sgx_cgroup *sgx_cg);
+void sgx_cgroup_reclaim_pages(struct misc_cg *root,  struct mm_struct *charge_mm);
 void sgx_cgroup_init(void);
 
 #endif
diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 7f92455d957d..68f28ff2d5ef 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -34,6 +34,16 @@ static struct sgx_epc_lru_list sgx_global_lru;
 
 static inline struct sgx_epc_lru_list *sgx_lru_list(struct sgx_epc_page *epc_page)
 {
+#ifdef CONFIG_CGROUP_SGX_EPC
+	if (epc_page->sgx_cg)
+		return &epc_page->sgx_cg->lru;
+
+	/*
+	 * This should not happen when cgroup is enabled: Every page belongs
+	 * to a cgroup, or the root by default.
+	 */
+	WARN_ON_ONCE(1);
+#endif
 	return &sgx_global_lru;
 }
 
@@ -42,7 +52,11 @@ static inline struct sgx_epc_lru_list *sgx_lru_list(struct sgx_epc_page *epc_pag
  */
 static inline bool sgx_can_reclaim(void)
 {
+#ifdef CONFIG_CGROUP_SGX_EPC
+	return !sgx_cgroup_lru_empty(misc_cg_root());
+#else
 	return !list_empty(&sgx_global_lru.reclaimable);
+#endif
 }
 
 static atomic_long_t sgx_nr_free_pages = ATOMIC_LONG_INIT(0);
@@ -404,7 +418,10 @@ static bool sgx_should_reclaim(unsigned long watermark)
 
 static void sgx_reclaim_pages_global(struct mm_struct *charge_mm)
 {
-	sgx_reclaim_pages(&sgx_global_lru, charge_mm);
+	if (IS_ENABLED(CONFIG_CGROUP_SGX_EPC))
+		sgx_cgroup_reclaim_pages(misc_cg_root(), charge_mm);
+	else
+		sgx_reclaim_pages(&sgx_global_lru, charge_mm);
 }
 
 /*
@@ -414,6 +431,16 @@ static void sgx_reclaim_pages_global(struct mm_struct *charge_mm)
  */
 void sgx_reclaim_direct(void)
 {
+#ifdef CONFIG_CGROUP_SGX_EPC
+	struct sgx_cgroup *sgx_cg = sgx_get_current_cg();
+
+	/* Make sure there are some free pages at cgroup level */
+	if (sgx_cg && sgx_cgroup_should_reclaim(sgx_cg)) {
+		sgx_cgroup_reclaim_pages(sgx_cg->cg, current->mm);
+		sgx_put_cg(sgx_cg);
+	}
+#endif
+	/* Make sure there are some free pages at global level */
 	if (sgx_should_reclaim(SGX_NR_LOW_PAGES))
 		sgx_reclaim_pages_global(current->mm);
 }
-- 
2.25.1