Convert sgx_reclaim_pages() to sgx_reclaim_page(), which reclaims only a
signle page and returns it back to the caller instead of freeing it.
A simpler flow will allow also simplify sgx_alloc_page() flow and make it
constant time. With this change it is easer to pin backing storage before
the pages are blocked, which stabilizes the EBLOCK/EWB/ETRACK flow: only an
EPCM conflict could cause a EWB to fail.
Because sgx_alloc_page() operations run in parallel on different threads
ETRACK's will still group multiple EBLOCK operations. ksgxswapd can be
improved in future with multi-threading (e.g.a work queue).
Cc: Sean Christoherson <sean.j.christopherson@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Serge Ayoun <serge.ayoun@xxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
---
Untested because I do not want to spend much time on this unless the
high level idea is welcomed.
arch/x86/kernel/cpu/sgx/main.c | 14 ++---
arch/x86/kernel/cpu/sgx/reclaim.c | 87 ++++++++++++++-----------------
arch/x86/kernel/cpu/sgx/sgx.h | 2 +-
3 files changed, 46 insertions(+), 57 deletions(-)
diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index e4f751651a65..7399ccd71fc1 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -71,8 +71,9 @@ static struct sgx_epc_page *sgx_try_alloc_page(void *owner)
struct sgx_epc_page *sgx_alloc_page(void *owner, bool reclaim)
{
struct sgx_epc_page *entry;
+ int i;
- for ( ; ; ) {
+ for (i = 0; i < SGX_NR_TO_SCAN; i++) {
entry = sgx_try_alloc_page(owner);
if (entry)
break;
@@ -85,13 +86,12 @@ struct sgx_epc_page *sgx_alloc_page(void *owner, bool reclaim)
break;
}
- if (signal_pending(current)) {
- entry = ERR_PTR(-ERESTARTSYS);
- break;
- }
+ entry = sgx_reclaim_page();
- sgx_reclaim_pages();
- schedule();
+ if (PTR_ERR(entry) == -EBUSY)
+ continue;
+ else
+ return entry;
}
if (sgx_calc_free_cnt() < SGX_NR_LOW_PAGES)
diff --git a/arch/x86/kernel/cpu/sgx/reclaim.c b/arch/x86/kernel/cpu/sgx/reclaim.c
index 3f10a8ff00b7..7908af4cbe70 100644
--- a/arch/x86/kernel/cpu/sgx/reclaim.c
+++ b/arch/x86/kernel/cpu/sgx/reclaim.c
@@ -69,6 +69,7 @@ static inline bool sgx_should_reclaim(void)
static int ksgxswapd(void *p)
{
+ struct sgx_epc_page *epc_page;
int i;
set_freezable();
@@ -83,8 +84,11 @@ static int ksgxswapd(void *p)
wait_event_freezable(ksgxswapd_waitq, kthread_should_stop() ||
sgx_should_reclaim());
- if (sgx_should_reclaim())
- sgx_reclaim_pages();
+ if (sgx_should_reclaim()) {
+ epc_page = sgx_reclaim_page();
+ if (!PTR_ERR_OR_ZERO(epc_page))
+ sgx_free_page(epc_page);
+ }
cond_resched();
}
@@ -390,73 +394,58 @@ static void sgx_reclaimer_write(struct sgx_epc_page *epc_page)
}
/**
- * sgx_reclaim_pages() - Reclaim EPC pages from the consumers
- * Takes a fixed chunk of pages from the global list of consumed EPC pages and
- * tries to swap them. Only the pages that are either being freed by the
- * consumer or actively used are skipped.
+ * sgx_reclaim_page() - Reclaim an EPC page
+ *
+ * Take an EPC page from the LRU list of active pages and write it to the
+ * regular memory unless it has been recently accessed or is being freed by the
+ * owner.
+ *
+ * Return:
+ * an &sgx_epc_page on success,
+ * -ENOMEM when the list is empty,
+ * -EBUSY when the page is not available,
+ * -errno otherwise
*/
-void sgx_reclaim_pages(void)
+struct sgx_epc_page *sgx_reclaim_page(void)
{
- struct sgx_epc_page *chunk[SGX_NR_TO_SCAN + 1];
struct sgx_epc_page *epc_page;
- struct sgx_epc_section *section;
- int i, j;
spin_lock(&sgx_active_page_list_lock);
- for (i = 0, j = 0; i < SGX_NR_TO_SCAN; i++) {
- if (list_empty(&sgx_active_page_list))
- break;
- epc_page = list_first_entry(&sgx_active_page_list,
- struct sgx_epc_page, list);
- list_del_init(&epc_page->list);
+ if (list_empty(&sgx_active_page_list)) {
+ spin_unlock(&sgx_active_page_list_lock);
+ return ERR_PTR(-ENOMEM);
+ }
- if (sgx_reclaimer_get(epc_page))
- chunk[j++] = epc_page;
- else
- /* The owner is freeing the page. No need to add the
- * page back to the list of reclaimable pages.
- */
- epc_page->desc &= ~SGX_EPC_PAGE_RECLAIMABLE;
+ epc_page = list_first_entry(&sgx_active_page_list,
+ struct sgx_epc_page, list);
+ list_del_init(&epc_page->list);
+
+ if (!sgx_reclaimer_get(epc_page)) {
+ epc_page->desc &= ~SGX_EPC_PAGE_RECLAIMABLE;
+ spin_unlock(&sgx_active_page_list_lock);
+ return ERR_PTR(-EBUSY);
}
- spin_unlock(&sgx_active_page_list_lock);
- for (i = 0; i < j; i++) {
- epc_page = chunk[i];
- if (sgx_reclaimer_evict(epc_page))
- continue;
+ spin_unlock(&sgx_active_page_list_lock);
+ if (!sgx_reclaimer_evict(epc_page)) {
sgx_reclaimer_put(epc_page);
spin_lock(&sgx_active_page_list_lock);
list_add_tail(&epc_page->list, &sgx_active_page_list);
spin_unlock(&sgx_active_page_list_lock);
- chunk[i] = NULL;
- }
-
- for (i = 0; i < j; i++) {
- epc_page = chunk[i];
- if (epc_page)
- sgx_reclaimer_block(epc_page);
+ return ERR_PTR(-EBUSY);
}
- for (i = 0; i < j; i++) {
- epc_page = chunk[i];
- if (epc_page) {
- sgx_reclaimer_write(epc_page);
- sgx_reclaimer_put(epc_page);
- epc_page->desc &= ~SGX_EPC_PAGE_RECLAIMABLE;
+ sgx_reclaimer_block(epc_page);
+ sgx_reclaimer_write(epc_page);
+ sgx_reclaimer_put(epc_page);
- section = sgx_epc_section(epc_page);
+ epc_page->desc &= ~SGX_EPC_PAGE_RECLAIMABLE;
- spin_lock(§ion->lock);
- list_add_tail(&epc_page->list,
- §ion->page_list);
- section->free_cnt++;
- spin_unlock(§ion->lock);
- }
- }
+ return epc_page;
}
unsigned long sgx_calc_free_cnt(void)
diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index f0ff7bd3d18e..faed25b2ccd6 100644
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -79,7 +79,7 @@ extern spinlock_t sgx_active_page_list_lock;
int sgx_page_reclaimer_init(void);
void sgx_mark_page_reclaimable(struct sgx_epc_page *page);
unsigned long sgx_calc_free_cnt(void);
-void sgx_reclaim_pages(void);
+struct sgx_epc_page *sgx_reclaim_page(void);
struct sgx_epc_page *sgx_alloc_page(void *owner, bool reclaim);
int __sgx_free_page(struct sgx_epc_page *page);
--
2.20.1
