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

Kristen Carlson Accardi
2022-09-22T17:13:12Z

From: Sean Christopherson <sean.j.christopherson@intel.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@intel.com>
Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Cc: Sean Christopherson <seanjc@google.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