linux-kernel - [RFC PATCH 15/20] x86/sgx: Add helper to grab pages from an arbitrary EPC LRU

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Message-Id: <20220922171057.1236139-16-kristen@linux.intel.com>
Date:   Thu, 22 Sep 2022 10:10:52 -0700
From:   Kristen Carlson Accardi <kristen@...ux.intel.com>
To:     linux-kernel@...r.kernel.org, linux-sgx@...r.kernel.org,
        cgroups@...r.kernel.org, Jarkko Sakkinen <jarkko@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>
Cc:     Kristen Carlson Accardi <kristen@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: [RFC PATCH 15/20] x86/sgx: Add helper to grab pages from an arbitrary EPC LRU

From: Sean Christopherson <sean.j.christopherson@...el.com>

Move the isolation loop into a standalone 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@...el.com>
Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
Cc: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kernel/cpu/sgx/main.c | 72 ++++++++++++++++++++--------------
 arch/x86/kernel/cpu/sgx/sgx.h  |  2 +
 2 files changed, 45 insertions(+), 29 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 1791881aa1b1..151ad720a4ec 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -280,10 +280,47 @@ static void sgx_reclaimer_write(struct sgx_epc_page *epc_page,
 }
 
 /**
- * sgx_reclaim_pages() - Reclaim EPC pages from the consumers
+ * 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 *lru, int *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)) {
+		if (list_empty(&lru->reclaimable))
+			break;
+
+		epc_page = list_first_entry(&lru->reclaimable,
+					    struct sgx_epc_page, list);
+
+		encl_page = epc_page->owner;
+		if (WARN_ON_ONCE(!(epc_page->flags & SGX_EPC_PAGE_ENCLAVE)))
+			continue;
+
+		if (kref_get_unless_zero(&encl_page->encl->refcount)) {
+			epc_page->flags |= 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
+			 */
+			epc_page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
+			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
- * @ignore_age:		 Reclaim a page even if it is young
+ * @nr_to_scan:		Number of EPC pages to scan for reclaim
+ * @ignore_age:		Reclaim a page even if it is young
  *
  * 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
@@ -302,42 +339,19 @@ static void sgx_reclaimer_write(struct sgx_epc_page *epc_page,
 int sgx_reclaim_epc_pages(int nr_to_scan, bool ignore_age)
 {
 	struct sgx_backing backing[SGX_MAX_NR_TO_RECLAIM];
-	struct sgx_encl_page *encl_page;
 	struct sgx_epc_page *epc_page, *tmp;
+	struct sgx_encl_page *encl_page;
 	struct sgx_epc_lru *lru;
 	pgoff_t page_index;
 	LIST_HEAD(iso);
+	int i = 0;
 	int ret;
-	int i;
-
-	spin_lock(&sgx_global_lru.lock);
-	for (i = 0; i < nr_to_scan; i++) {
-		if (list_empty(&sgx_global_lru.reclaimable))
-			break;
-
-		epc_page = list_first_entry(&sgx_global_lru.reclaimable,
-					    struct sgx_epc_page, list);
-		encl_page = epc_page->owner;
-		if (WARN_ON_ONCE(!(epc_page->flags & SGX_EPC_PAGE_ENCLAVE)))
-			continue;
 
-		if (kref_get_unless_zero(&encl_page->encl->refcount) != 0) {
-			epc_page->flags |= 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
-			 */
-			epc_page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
-			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))
 		goto out;
 
-	i = 0;
 	list_for_each_entry_safe(epc_page, tmp, &iso, list) {
 		encl_page = epc_page->owner;
 
diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index a2042303a666..0598d534371b 100644
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -114,6 +114,8 @@ 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);
 int sgx_reclaim_epc_pages(int nr_to_scan, bool ignore_age);
+void sgx_isolate_epc_pages(struct sgx_epc_lru *lru, int *nr_to_scan,
+			   struct list_head *dst);
 
 void sgx_ipi_cb(void *info);
 
-- 
2.37.3