linux-kernel - [RFC PATCH 07/20] x86/sgx: Use a list to track to-be-reclaimed pages during reclaim

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Message-Id: <20220922171057.1236139-8-kristen@linux.intel.com>
Date:   Thu, 22 Sep 2022 10:10:44 -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 07/20] x86/sgx: Use a list to track to-be-reclaimed pages during reclaim

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

Change sgx_reclaim_pages() to use a list rather than an array for
storing the epc_pages which will be reclaimed. This change is needed
to transition to the LRU implementation for EPC cgroup support.

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 | 43 +++++++++++++++-------------------
 1 file changed, 19 insertions(+), 24 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 93aa9e09c26d..085c06fdc359 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -288,12 +288,11 @@ static void sgx_reclaimer_write(struct sgx_epc_page *epc_page,
  */
 static void sgx_reclaim_pages(void)
 {
-	struct sgx_epc_page *chunk[SGX_NR_TO_SCAN];
 	struct sgx_backing backing[SGX_NR_TO_SCAN];
 	struct sgx_encl_page *encl_page;
-	struct sgx_epc_page *epc_page;
+	struct sgx_epc_page *epc_page, *tmp;
 	pgoff_t page_index;
-	int cnt = 0;
+	LIST_HEAD(iso);
 	int ret;
 	int i;
 
@@ -304,23 +303,26 @@ static void sgx_reclaim_pages(void)
 
 		epc_page = list_first_entry(&sgx_global_lru.reclaimable,
 					    struct sgx_epc_page, list);
-		list_del_init(&epc_page->list);
 		encl_page = epc_page->owner;
 
 		if (kref_get_unless_zero(&encl_page->encl->refcount) != 0) {
 			epc_page->flags |= SGX_EPC_PAGE_RECLAIM_IN_PROGRESS;
-			chunk[cnt++] = epc_page;
+			list_move_tail(&epc_page->list, &iso);
 		} else {
-			/* The owner is freeing the page. No need to add the
-			 * page back to the list of reclaimable pages.
+			/* 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);
 
-	for (i = 0; i < cnt; i++) {
-		epc_page = chunk[i];
+	if (list_empty(&iso))
+		goto out;
+
+	i = 0;
+	list_for_each_entry_safe(epc_page, tmp, &iso, list) {
 		encl_page = epc_page->owner;
 
 		if (!sgx_reclaimer_age(epc_page))
@@ -335,6 +337,7 @@ static void sgx_reclaim_pages(void)
 			goto skip;
 		}
 
+		i++;
 		encl_page->desc |= SGX_ENCL_PAGE_BEING_RECLAIMED;
 		mutex_unlock(&encl_page->encl->lock);
 		continue;
@@ -342,27 +345,19 @@ static void sgx_reclaim_pages(void)
 skip:
 		spin_lock(&sgx_global_lru.lock);
 		epc_page->flags &= ~SGX_EPC_PAGE_RECLAIM_IN_PROGRESS;
-		list_add_tail(&epc_page->list, &sgx_global_lru.reclaimable);
+		list_move_tail(&epc_page->list, &sgx_global_lru.reclaimable);
 		spin_unlock(&sgx_global_lru.lock);
 
 		kref_put(&encl_page->encl->refcount, sgx_encl_release);
-
-		chunk[i] = NULL;
-	}
-
-	for (i = 0; i < cnt; i++) {
-		epc_page = chunk[i];
-		if (epc_page)
-			sgx_reclaimer_block(epc_page);
 	}
 
-	for (i = 0; i < cnt; i++) {
-		epc_page = chunk[i];
-		if (!epc_page)
-			continue;
+	list_for_each_entry(epc_page, &iso, list)
+		sgx_reclaimer_block(epc_page);
 
+	i= 0;
+	list_for_each_entry_safe(epc_page, tmp, &iso, list) {
 		encl_page = epc_page->owner;
-		sgx_reclaimer_write(epc_page, &backing[i]);
+		sgx_reclaimer_write(epc_page, &backing[i++]);
 
 		kref_put(&encl_page->encl->refcount, sgx_encl_release);
 		epc_page->flags &= ~(SGX_EPC_PAGE_RECLAIMER_TRACKED |
@@ -370,7 +365,7 @@ static void sgx_reclaim_pages(void)
 
 		sgx_free_epc_page(epc_page);
 	}
-
+out:
 	cond_resched();
 }
 
-- 
2.37.3