[PATCH v4 0/2] Take away EREMOVE from sgx_free_epc_page()

[PATCH v4 0/2] Take away EREMOVE from sgx_free_epc_page()

[jarkko]

From: "jarkko@kernel.org" <jarkko@kernel.org>

Refactor EREMOVE out of sgx_free_epc_page() since it is only used in
one function.

v4:
- No code changes to v4. Re-send because of
  "-to linux@sgx.vger.kernel.org"

jarkko@kernel.org (2):
  x86/sgx: Remove a warn from sgx_free_epc_page()
  x86/sgx: Wipe out EREMOVE from sgx_free_epc_page()

 arch/x86/kernel/cpu/sgx/encl.c | 13 +++++++++++++
 arch/x86/kernel/cpu/sgx/main.c | 12 ++++--------
 2 files changed, 17 insertions(+), 8 deletions(-)

-- 
2.29.2

[PATCH v4 1/2] x86/sgx: Remove a warn from sgx_free_epc_page()

[jarkko]

From: "jarkko@kernel.org" <jarkko@kernel.org>

Remove SGX_EPC_PAGE_RECLAIMER_TRACKED check and warning. This cannot
happen, as enclave pages are freed only at the time when encl->refcount
triggers, i.e. when both VFS and the page reclaimer have given up on
their references.

Signed-off-by: jarkko@kernel.org <jarkko@kernel.org>
---
 arch/x86/kernel/cpu/sgx/main.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index c519fc5f6948..ebbd3b97b3d0 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -605,8 +605,6 @@ void sgx_free_epc_page(struct sgx_epc_page *page)
 	struct sgx_epc_section *section = &sgx_epc_sections[page->section];
 	int ret;
 
-	WARN_ON_ONCE(page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED);
-
 	ret = __eremove(sgx_get_epc_virt_addr(page));
 	if (WARN_ONCE(ret, "EREMOVE returned %d (0x%x)", ret, ret))
 		return;
-- 
2.29.2

[PATCH v4 2/2] x86/sgx: Wipe out EREMOVE from sgx_free_epc_page()

[jarkko]

From: "jarkko@kernel.org" <jarkko@kernel.org>

Encapsulate the snippet in sgx_free_epc_page() concerning EREMOVE to
sgx_reset_epc_page(), which is a static helper function for
sgx_encl_release(). It's the only function existing, which deals with
initialized pages.

Signed-off-by: jarkko@kernel.org <jarkko@kernel.org>
---
v3: Fixed va_page desctruction.
v2: Fixed a compilation error s/page/epc_page/ change not amended
    to the patches.
 arch/x86/kernel/cpu/sgx/encl.c | 13 +++++++++++++
 arch/x86/kernel/cpu/sgx/main.c | 10 ++++------
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index ee50a5010277..a78b71447771 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -389,6 +389,16 @@ const struct vm_operations_struct sgx_vm_ops = {
 	.access = sgx_vma_access,
 };
 
+
+static void sgx_reset_epc_page(struct sgx_epc_page *epc_page)
+{
+	int ret;
+
+	ret = __eremove(sgx_get_epc_virt_addr(epc_page));
+	if (WARN_ONCE(ret, "EREMOVE returned %d (0x%x)", ret, ret))
+		return;
+}
+
 /**
  * sgx_encl_release - Destroy an enclave instance
  * @kref:	address of a kref inside &sgx_encl
@@ -412,6 +422,7 @@ void sgx_encl_release(struct kref *ref)
 			if (sgx_unmark_page_reclaimable(entry->epc_page))
 				continue;
 
+			sgx_reset_epc_page(entry->epc_page);
 			sgx_free_epc_page(entry->epc_page);
 			encl->secs_child_cnt--;
 			entry->epc_page = NULL;
@@ -423,6 +434,7 @@ void sgx_encl_release(struct kref *ref)
 	xa_destroy(&encl->page_array);
 
 	if (!encl->secs_child_cnt && encl->secs.epc_page) {
+		sgx_reset_epc_page(encl->secs.epc_page);
 		sgx_free_epc_page(encl->secs.epc_page);
 		encl->secs.epc_page = NULL;
 	}
@@ -431,6 +443,7 @@ void sgx_encl_release(struct kref *ref)
 		va_page = list_first_entry(&encl->va_pages, struct sgx_va_page,
 					   list);
 		list_del(&va_page->list);
+		sgx_reset_epc_page(va_page->epc_page);
 		sgx_free_epc_page(va_page->epc_page);
 		kfree(va_page);
 	}
diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index ebbd3b97b3d0..5e20b42f2639 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -598,16 +598,14 @@ struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim)
  * sgx_free_epc_page() - Free an EPC page
  * @page:	an EPC page
  *
- * Call EREMOVE for an EPC page and insert it back to the list of free pages.
+ * Put the EPC page back to the list of free pages. It's the callers
+ * responsibility to make sure that the page is in uninitialized state In other
+ * words, do EREMOVE, EWB or whatever operation is necessary before calling
+ * this function.
  */
 void sgx_free_epc_page(struct sgx_epc_page *page)
 {
 	struct sgx_epc_section *section = &sgx_epc_sections[page->section];
-	int ret;
-
-	ret = __eremove(sgx_get_epc_virt_addr(page));
-	if (WARN_ONCE(ret, "EREMOVE returned %d (0x%x)", ret, ret))
-		return;
 
 	spin_lock(&section->lock);
 	list_add_tail(&page->list, &section->page_list);
-- 
2.29.2