[PATCH v4 14/18] x86/sgx: Add helper to grab pages from an arbitrary EPC LRU

[Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>]

From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>

Move the isolation loop into a helper, sgx_isolate_pages(), in
preparation for existence of multiple LRUs. Expose the helper to other
SGX code so that it can be called from the EPC cgroup code, e.g., to
isolate pages from a single cgroup LRU. Exposing the isolation loop
allows the cgroup iteration logic to be wholly encapsulated within the
cgroup code.

Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx>
Signed-off-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
---
V4:
- No changes other than reordering the patches
---
 arch/x86/kernel/cpu/sgx/main.c | 57 +++++++++++++++++++++-------------
 arch/x86/kernel/cpu/sgx/sgx.h  |  2 ++
 2 files changed, 37 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index e1dde431a400..ce316bd5e5bb 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -283,6 +283,40 @@ static void sgx_reclaimer_write(struct sgx_epc_page *epc_page,
 	mutex_unlock(&encl->lock);
 }
 
+/**
+ * sgx_isolate_epc_pages() - Isolate pages from an LRU for reclaim
+ * @lru:	LRU from which to reclaim
+ * @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,
+			   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) {
+		epc_page = list_first_entry_or_null(&lru->reclaimable, struct sgx_epc_page, list);
+		if (!epc_page)
+			break;
+
+		encl_page = epc_page->encl_page;
+
+		if (kref_get_unless_zero(&encl_page->encl->refcount)) {
+			sgx_epc_page_set_state(epc_page, SGX_EPC_PAGE_RECLAIM_IN_PROGRESS);
+			list_move_tail(&epc_page->list, dst);
+		} else {
+			/* The owner is freeing the page, remove it from the
+			 * LRU list
+			 */
+			sgx_epc_page_reset_state(epc_page);
+			list_del_init(&epc_page->list);
+		}
+	}
+	spin_unlock(&lru->lock);
+}
+
 /**
  * sgx_reclaim_epc_pages() - Reclaim EPC pages from the consumers
  * @nr_to_scan:		 Number of EPC pages to scan for reclaim
@@ -310,28 +344,7 @@ size_t sgx_reclaim_epc_pages(size_t nr_to_scan, bool ignore_age)
 	size_t ret;
 	size_t i;
 
-	spin_lock(&sgx_global_lru.lock);
-	for (i = 0; i < SGX_NR_TO_SCAN; i++) {
-		epc_page = list_first_entry_or_null(&sgx_global_lru.reclaimable,
-						    struct sgx_epc_page, list);
-		if (!epc_page)
-			break;
-
-		list_del_init(&epc_page->list);
-		encl_page = epc_page->encl_page;
-
-		if (kref_get_unless_zero(&encl_page->encl->refcount) != 0) {
-			sgx_epc_page_set_state(epc_page, SGX_EPC_PAGE_RECLAIM_IN_PROGRESS);
-			list_move_tail(&epc_page->list, &iso);
-		} else {
-			/* The owner is freeing the page, remove it from the
-			 * LRU list
-			 */
-			sgx_epc_page_reset_state(epc_page);
-			list_del_init(&epc_page->list);
-		}
-	}
-	spin_unlock(&sgx_global_lru.lock);
+	sgx_isolate_epc_pages(&sgx_global_lru, nr_to_scan, &iso);
 
 	if (list_empty(&iso))
 		return 0;
diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index aa4ec2c0ce96..7e21192b87a8 100644
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -178,6 +178,8 @@ 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,
+			   struct list_head *dst);
 
 void sgx_ipi_cb(void *info);
 
-- 
2.25.1