The page reclaimer thread sets SGX_ENC_PAGE_BEING_RECLAIMED flag when
the enclave page is being reclaimed (moved to the backing store). This
flag however has two logical meanings:
1. Don't attempt to load the enclave page (the page is busy), see
__sgx_encl_load_page().
2. Don't attempt to remove the PCMD page corresponding to this enclave
page (the PCMD page is busy), see reclaimer_writing_to_pcmd().
To reflect these two meanings, split SGX_ENCL_PAGE_BEING_RECLAIMED into
two flags: SGX_ENCL_PAGE_BUSY and SGX_ENCL_PAGE_PCMD_BUSY. Currently,
both flags are set only when the enclave page is being reclaimed (by the
page reclaimer thread). A future commit will introduce new cases when
the enclave page is being operated on; these new cases will set only the
SGX_ENCL_PAGE_BUSY flag.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Dmitrii Kuvaiskii <dmitrii.kuvaiskii@xxxxxxxxx>
Reviewed-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Acked-by: Kai Huang <kai.huang@xxxxxxxxx>
---
arch/x86/kernel/cpu/sgx/encl.c | 16 +++++++---------
arch/x86/kernel/cpu/sgx/encl.h | 10 ++++++++--
arch/x86/kernel/cpu/sgx/main.c | 4 ++--
3 files changed, 17 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index 279148e72459..c0a3c00284c8 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -46,10 +46,10 @@ static int sgx_encl_lookup_backing(struct sgx_encl *encl, unsigned long page_ind
* a check if an enclave page sharing the PCMD page is in the process of being
* reclaimed.
*
- * The reclaimer sets the SGX_ENCL_PAGE_BEING_RECLAIMED flag when it
- * intends to reclaim that enclave page - it means that the PCMD page
- * associated with that enclave page is about to get some data and thus
- * even if the PCMD page is empty, it should not be truncated.
+ * The reclaimer sets the SGX_ENCL_PAGE_PCMD_BUSY flag when it intends to
+ * reclaim that enclave page - it means that the PCMD page associated with that
+ * enclave page is about to get some data and thus even if the PCMD page is
+ * empty, it should not be truncated.
*
* Context: Enclave mutex (&sgx_encl->lock) must be held.
* Return: 1 if the reclaimer is about to write to the PCMD page
@@ -77,8 +77,7 @@ static int reclaimer_writing_to_pcmd(struct sgx_encl *encl,
* Stop when reaching the SECS page - it does not
* have a page_array entry and its reclaim is
* started and completed with enclave mutex held so
- * it does not use the SGX_ENCL_PAGE_BEING_RECLAIMED
- * flag.
+ * it does not use the SGX_ENCL_PAGE_PCMD_BUSY flag.
*/
if (addr == encl->base + encl->size)
break;
@@ -91,8 +90,7 @@ static int reclaimer_writing_to_pcmd(struct sgx_encl *encl,
* VA page slot ID uses same bit as the flag so it is important
* to ensure that the page is not already in backing store.
*/
- if (entry->epc_page &&
- (entry->desc & SGX_ENCL_PAGE_BEING_RECLAIMED)) {
+ if (entry->epc_page && (entry->desc & SGX_ENCL_PAGE_PCMD_BUSY)) {
reclaimed = 1;
break;
}
@@ -257,7 +255,7 @@ static struct sgx_encl_page *__sgx_encl_load_page(struct sgx_encl *encl,
/* Entry successfully located. */
if (entry->epc_page) {
- if (entry->desc & SGX_ENCL_PAGE_BEING_RECLAIMED)
+ if (entry->desc & SGX_ENCL_PAGE_BUSY)
return ERR_PTR(-EBUSY);
return entry;
diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h
index f94ff14c9486..b566b8ad5f33 100644
--- a/arch/x86/kernel/cpu/sgx/encl.h
+++ b/arch/x86/kernel/cpu/sgx/encl.h
@@ -22,8 +22,14 @@
/* 'desc' bits holding the offset in the VA (version array) page. */
#define SGX_ENCL_PAGE_VA_OFFSET_MASK GENMASK_ULL(11, 3)
-/* 'desc' bit marking that the page is being reclaimed. */
-#define SGX_ENCL_PAGE_BEING_RECLAIMED BIT(3)
+/* 'desc' bit indicating that the page is busy (being reclaimed). */
+#define SGX_ENCL_PAGE_BUSY BIT(2)
+
+/*
+ * 'desc' bit indicating that PCMD page associated with the enclave page is
+ * busy (because the enclave page is being reclaimed).
+ */
+#define SGX_ENCL_PAGE_PCMD_BUSY BIT(3)
struct sgx_encl_page {
unsigned long desc;
diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index f3f1461273ee..da59f034b769 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -205,7 +205,7 @@ static void sgx_encl_ewb(struct sgx_epc_page *epc_page,
void *va_slot;
int ret;
- encl_page->desc &= ~SGX_ENCL_PAGE_BEING_RECLAIMED;
+ encl_page->desc &= ~(SGX_ENCL_PAGE_BUSY | SGX_ENCL_PAGE_PCMD_BUSY);
va_page = list_first_entry(&encl->va_pages, struct sgx_va_page,
list);
@@ -341,7 +341,7 @@ static void sgx_reclaim_pages(void)
goto skip;
}
- encl_page->desc |= SGX_ENCL_PAGE_BEING_RECLAIMED;
+ encl_page->desc |= SGX_ENCL_PAGE_BUSY | SGX_ENCL_PAGE_PCMD_BUSY;
mutex_unlock(&encl_page->encl->lock);
continue;
--
2.43.0
