diff mbox series

[v5,08/18] x86/sgx: Use a list to track to-be-reclaimed pages

Message ID 20230923030657.16148-9-haitao.huang@linux.intel.com
State New
Headers
Series Add Cgroup support for SGX EPC memory |

Commit Message

Haitao Huang Sept. 23, 2023, 3:06 a.m. UTC 
  From: Sean Christopherson <sean.j.christopherson@intel.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.

When the EPC cgroup is implemented, the reclaiming process will do a
pre-order tree walk for the subtree starting from the limit-violating
cgroup.  When each node is visited, candidate pages are selected from
its "reclaimable" LRU list and moved into this temporary list. Passing a
list from node to node for temporary storage in this walk is more
straightforward than using an array.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Co-developed-by: Kristen Carlson Accardi <kristen@linux.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>
Cc: Sean Christopherson <seanjc@google.com>
---
V4:
- Changes needed for patch reordering
- Revised commit message

V3:
- Removed list wrappers
---
 arch/x86/kernel/cpu/sgx/main.c | 40 +++++++++++++++-------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

Comments

Kai Huang Sept. 28, 2023, 9:28 a.m. UTC | #1 
On Fri, 2023-09-22 at 20:06 -0700, Haitao Huang wrote:
> @@ -314,18 +313,22 @@ static void sgx_reclaim_pages(void)
>  
>  		if (kref_get_unless_zero(&encl_page->encl->refcount) != 0) {
>  			sgx_epc_page_set_state(epc_page, 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
>  			 */

Please fix comment style.

>  			sgx_epc_page_reset_state(epc_page);
> +			list_del_init(&epc_page->list);

Is this still needed?  It seems list_del_init() has been done when the EPC page
is taken off from the global active list?
Haitao Huang Oct. 3, 2023, 5:09 a.m. UTC | #2 
On Thu, 28 Sep 2023 04:28:34 -0500, Huang, Kai <kai.huang@intel.com> wrote:

> On Fri, 2023-09-22 at 20:06 -0700, Haitao Huang wrote:
>> @@ -314,18 +313,22 @@ static void sgx_reclaim_pages(void)
>>   		if (kref_get_unless_zero(&encl_page->encl->refcount) != 0) {
>>  			sgx_epc_page_set_state(epc_page, 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
>>  			 */
>
> Please fix comment style.

Sure

>
>>  			sgx_epc_page_reset_state(epc_page);
>> +			list_del_init(&epc_page->list);
>
> Is this still needed?  It seems list_del_init() has been done when the  
> EPC page
> is taken off from the global active list?
>

Good catch. I'll remove it.

Thanks
Haitao
diff mbox series

Patch

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index c1ae19a154d0..fba06dc5abfe 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -293,12 +293,11 @@  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_epc_page *epc_page, *tmp;
 	struct sgx_encl_page *encl_page;
-	struct sgx_epc_page *epc_page;
 	pgoff_t page_index;
-	int cnt = 0;
+	LIST_HEAD(iso);
 	int ret;
 	int i;
 
@@ -314,18 +313,22 @@  static void sgx_reclaim_pages(void)
 
 		if (kref_get_unless_zero(&encl_page->encl->refcount) != 0) {
 			sgx_epc_page_set_state(epc_page, 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
 			 */
 			sgx_epc_page_reset_state(epc_page);
+			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))
+		return;
+
+	i = 0;
+	list_for_each_entry_safe(epc_page, tmp, &iso, list) {
 		encl_page = epc_page->owner;
 
 		if (!sgx_reclaimer_age(epc_page))
@@ -340,6 +343,7 @@  static void sgx_reclaim_pages(void)
 			goto skip;
 		}
 
+		i++;
 		encl_page->desc |= SGX_ENCL_PAGE_BEING_RECLAIMED;
 		mutex_unlock(&encl_page->encl->lock);
 		continue;
@@ -347,27 +351,19 @@  static void sgx_reclaim_pages(void)
 skip:
 		spin_lock(&sgx_global_lru.lock);
 		sgx_epc_page_set_state(epc_page, SGX_EPC_PAGE_RECLAIMABLE);
-		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);
 		sgx_epc_page_reset_state(epc_page);