[PATCH v2 13/17] x86/sgx: Introduce sgx_can_reclaim()

[Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>]

Make sgx_reclaim_evict() idempotennt and rename it to sgx_can_reclaim() and
set SGX_ENCL_PAGE_RECLAIMED in the call site.

Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Cc: Shay Katz-zamir <shay.katz-zamir@xxxxxxxxx>
Cc: Serge Ayoun <serge.ayoun@xxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/cpu/sgx/reclaim.c | 32 +++++++++++++++++--------------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/reclaim.c b/arch/x86/kernel/cpu/sgx/reclaim.c
index 46850d61c940..e2e2ff282eb3 100644
--- a/arch/x86/kernel/cpu/sgx/reclaim.c
+++ b/arch/x86/kernel/cpu/sgx/reclaim.c
@@ -121,7 +121,19 @@ void sgx_mark_page_reclaimable(struct sgx_epc_page *page)
 	spin_unlock(&sgx_active_page_list_lock);
 }
 
-static bool sgx_reclaimer_evict(struct sgx_epc_page *epc_page)
+/**
+ * sgx_can_reclaim() - Filter out the pages that should not be reclaimed
+ * @epc_page:	a candidate EPC page
+ *
+ * Do not reclaim this page if it has been recently accessed by any mm_struct
+ * *and* if the enclave is still alive.  No need to take the enclave's lock,
+ * worst case scenario reclaiming pages from a dead enclave is delayed slightly.
+ * A live enclave with a recently accessed page is more common and avoiding lock
+ * contention in that case is a boon to performance.
+ *
+ * Return: true if the page should be reclaimed
+ */
+static bool sgx_can_reclaim(struct sgx_epc_page *epc_page)
 {
 	struct sgx_encl_page *page = epc_page->owner;
 	struct sgx_encl *encl = page->encl;
@@ -147,21 +159,9 @@ static bool sgx_reclaimer_evict(struct sgx_epc_page *epc_page)
 
 	srcu_read_unlock(&encl->srcu, idx);
 
-	/*
-	 * Do not reclaim this page if it has been recently accessed by any
-	 * mm_struct *and* if the enclave is still alive.  No need to take
-	 * the enclave's lock, worst case scenario reclaiming pages from a
-	 * dead enclave is delayed slightly.  A live enclave with a recently
-	 * accessed page is more common and avoiding lock contention in that
-	 * case is a boon to performance.
-	 */
 	if (!ret && !(atomic_read(&encl->flags) & SGX_ENCL_DEAD))
 		return false;
 
-	mutex_lock(&encl->lock);
-	page->desc |= SGX_ENCL_PAGE_RECLAIMED;
-	mutex_unlock(&encl->lock);
-
 	return true;
 }
 
@@ -405,8 +405,12 @@ void sgx_reclaim_pages(void)
 		epc_page = chunk[i];
 		encl_page = epc_page->owner;
 
-		if (sgx_reclaimer_evict(epc_page))
+		if (sgx_can_reclaim(epc_page)) {
+			mutex_lock(&encl_page->encl->lock);
+			encl_page->desc |= SGX_ENCL_PAGE_RECLAIMED;
+			mutex_unlock(&encl_page->encl->lock);
 			continue;
+		}
 
 		kref_put(&encl_page->encl->refcount, sgx_encl_release);
 
-- 
2.20.1