[PATCH] x86/sgx: WARN once if EREMOVE fails when killing an enclave

[Sean Christopherson <sean.j.christopherson@intel.com>]

WARN if EREMOVE fails when destroying an enclave.  sgx_encl_release()
uses the non-WARN __sgx_free_page() when freeing pages as some pages may
be in the process of being reclaimed, i.e. are owned by the reclaimer.
But EREMOVE should never fail as sgx_encl_destroy() is only called when
the enclave cannot have active threads, e.g. prior to EINIT and when the
enclave is being released.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/kernel/cpu/sgx/encl.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index 54ca827e68a9..a6786e7ae40e 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -463,16 +463,23 @@ void sgx_encl_destroy(struct sgx_encl *encl)
 	struct sgx_encl_page *entry;
 	struct radix_tree_iter iter;
 	void **slot;
+	int r;
 
 	atomic_or(SGX_ENCL_DEAD, &encl->flags);
 
 	radix_tree_for_each_slot(slot, &encl->page_tree, &iter, 0) {
 		entry = *slot;
 		if (entry->epc_page) {
-			if (!__sgx_free_page(entry->epc_page)) {
+			/*
+			 * Freeing the page can fail if it's in the process of
+			 * being reclaimed (-EBUSY), but EREMOVE itself should
+			 * not fail at this point.
+			 */
+			r = __sgx_free_page(entry->epc_page);
+			WARN_ONCE(r > 0, "sgx: EREMOVE returned %d (0x%x)", r, r);
+			if (!r) {
 				encl->secs_child_cnt--;
 				entry->epc_page = NULL;
-
 			}
 
 			radix_tree_delete(&entry->encl->page_tree,
-- 
2.22.0