[PATCH v8 10/15] x86/sgx: Add EPC reclamation in cgroup try_charge()

[Haitao Huang]

From: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx>

When the EPC usage of a cgroup is near its limit, the cgroup needs to
reclaim pages used in the same cgroup to make room for new allocations.
This is analogous to the behavior that the global reclaimer is triggered
when the global usage is close to total available EPC.

Add a Boolean parameter for sgx_epc_cgroup_try_charge() to indicate
whether synchronous reclaim is allowed or not. And trigger the
synchronous/asynchronous reclamation flow accordingly.

Note at this point, all reclaimable EPC pages are still tracked in the
global LRU and per-cgroup LRUs are empty. So no per-cgroup reclamation
is activated yet.

Co-developed-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx>
Co-developed-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
Signed-off-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
---
V7:
- Split this out from the big patch, #10 in V6. (Dave, Kai)
---
 arch/x86/kernel/cpu/sgx/epc_cgroup.c | 26 ++++++++++++++++++++++++--
 arch/x86/kernel/cpu/sgx/epc_cgroup.h |  4 ++--
 arch/x86/kernel/cpu/sgx/main.c       |  2 +-
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/epc_cgroup.c b/arch/x86/kernel/cpu/sgx/epc_cgroup.c
index cbcb7b0de3fe..127f515ffccf 100644
--- a/arch/x86/kernel/cpu/sgx/epc_cgroup.c
+++ b/arch/x86/kernel/cpu/sgx/epc_cgroup.c
@@ -176,13 +176,35 @@ static void sgx_epc_cgroup_reclaim_work_func(struct work_struct *work)
 /**
  * sgx_epc_cgroup_try_charge() - try to charge cgroup for a single EPC page
  * @epc_cg:	The EPC cgroup to be charged for the page.
+ * @reclaim:	Whether or not synchronous reclaim is allowed
  * Return:
  * * %0 - If successfully charged.
  * * -errno - for failures.
  */
-int sgx_epc_cgroup_try_charge(struct sgx_epc_cgroup *epc_cg)
+int sgx_epc_cgroup_try_charge(struct sgx_epc_cgroup *epc_cg, bool reclaim)
 {
-	return misc_cg_try_charge(MISC_CG_RES_SGX_EPC, epc_cg->cg, PAGE_SIZE);
+	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->cg))
+			return -ENOMEM;
+
+		if (signal_pending(current))
+			return -ERESTARTSYS;
+
+		if (!reclaim) {
+			queue_work(sgx_epc_cg_wq, &epc_cg->reclaim_work);
+			return -EBUSY;
+		}
+
+		if (!sgx_epc_cgroup_reclaim_pages(epc_cg->cg, false))
+			/* All pages were too young to reclaim, try again a little later */
+			schedule();
+	}
+
+	return 0;
 }
 
 /**
diff --git a/arch/x86/kernel/cpu/sgx/epc_cgroup.h b/arch/x86/kernel/cpu/sgx/epc_cgroup.h
index e3c6a08f0ee8..d061cd807b45 100644
--- a/arch/x86/kernel/cpu/sgx/epc_cgroup.h
+++ b/arch/x86/kernel/cpu/sgx/epc_cgroup.h
@@ -23,7 +23,7 @@ static inline struct sgx_epc_cgroup *sgx_get_current_epc_cg(void)
 
 static inline void sgx_put_epc_cg(struct sgx_epc_cgroup *epc_cg) { }
 
-static inline int sgx_epc_cgroup_try_charge(struct sgx_epc_cgroup *epc_cg)
+static inline int sgx_epc_cgroup_try_charge(struct sgx_epc_cgroup *epc_cg, bool reclaim)
 {
 	return 0;
 }
@@ -66,7 +66,7 @@ static inline void sgx_put_epc_cg(struct sgx_epc_cgroup *epc_cg)
 		put_misc_cg(epc_cg->cg);
 }
 
-int sgx_epc_cgroup_try_charge(struct sgx_epc_cgroup *epc_cg);
+int sgx_epc_cgroup_try_charge(struct sgx_epc_cgroup *epc_cg, bool reclaim);
 void sgx_epc_cgroup_uncharge(struct sgx_epc_cgroup *epc_cg);
 bool sgx_epc_cgroup_lru_empty(struct misc_cg *root);
 void sgx_epc_cgroup_init(void);
diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 51904f191b97..2279ae967707 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -588,7 +588,7 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim)
 	int ret;
 
 	epc_cg = sgx_get_current_epc_cg();
-	ret = sgx_epc_cgroup_try_charge(epc_cg);
+	ret = sgx_epc_cgroup_try_charge(epc_cg, reclaim);
 	if (ret) {
 		sgx_put_epc_cg(epc_cg);
 		return ERR_PTR(ret);
-- 
2.25.1