[PATCH v4 08/18] x86/sgx: Use a list to track to-be-reclaimed pages

Haitao Huang
2023-09-13T04:06:25Z

From: Kristen Carlson Accardi <kristen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>

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-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Kristen Carlson Accardi <kristen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Signed-off-by: Haitao Huang<haitao.huang-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Cc: Sean Christopherson <seanjc-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
---
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(-)

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);
--
2.25.1