[PATCH v5 06/18] x86/sgx: Introduce EPC page states

Haitao Huang
2023-09-23T03:07:18Z

Use the lower 3 bits in the flags field of sgx_epc_page struct to
track EPC states in its life cycle and define an enum for possible
states. More state(s) will be added later.

Signed-off-by: Haitao Huang <haitao.huang@linux.intel.com>
---
V4:
- No changes other than required for patch reordering.

V3:
- This is new in V3 to replace the bit mask based approach (requested by Jarkko)
---
arch/x86/kernel/cpu/sgx/encl.c | 14 +++++++---
arch/x86/kernel/cpu/sgx/ioctl.c | 7 +++--
arch/x86/kernel/cpu/sgx/main.c | 19 +++++++------
arch/x86/kernel/cpu/sgx/sgx.h | 49 ++++++++++++++++++++++++++++++---
4 files changed, 71 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index 97a53e34a8b4..f5afc8d65e22 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -244,8 +244,12 @@ static struct sgx_epc_page *sgx_encl_load_secs(struct sgx_encl *encl)
{
struct sgx_epc_page *epc_page = encl->secs.epc_page;

- if (!epc_page)
+ if (!epc_page) {
epc_page = sgx_encl_eldu(&encl->secs, NULL);
+ if (!IS_ERR(epc_page))
+ sgx_record_epc_page(epc_page,
+ SGX_EPC_PAGE_UNRECLAIMABLE);
+ }

return epc_page;
}
@@ -272,7 +276,7 @@ static struct sgx_encl_page *__sgx_encl_load_page(struct sgx_encl *encl,
return ERR_CAST(epc_page);

encl->secs_child_cnt++;
- sgx_record_epc_page(epc_page, SGX_EPC_PAGE_RECLAIMER_TRACKED);
+ sgx_record_epc_page(epc_page, SGX_EPC_PAGE_RECLAIMABLE);

return entry;
}
@@ -398,7 +402,7 @@ static vm_fault_t sgx_encl_eaug_page(struct vm_area_struct *vma,
encl_page->type = SGX_PAGE_TYPE_REG;
encl->secs_child_cnt++;

- sgx_record_epc_page(epc_page, SGX_EPC_PAGE_RECLAIMER_TRACKED);
+ sgx_record_epc_page(epc_page, SGX_EPC_PAGE_RECLAIMABLE);

phys_addr = sgx_get_epc_phys_addr(epc_page);
/*
@@ -1256,6 +1260,8 @@ struct sgx_epc_page *sgx_alloc_va_page(bool reclaim)
sgx_encl_free_epc_page(epc_page);
return ERR_PTR(-EFAULT);
}
+ sgx_record_epc_page(epc_page,
+ SGX_EPC_PAGE_UNRECLAIMABLE);

return epc_page;
}
@@ -1315,7 +1321,7 @@ void sgx_encl_free_epc_page(struct sgx_epc_page *page)
{
int ret;

- WARN_ON_ONCE(page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED);
+ WARN_ON_ONCE(page->flags & SGX_EPC_PAGE_STATE_MASK);

ret = __eremove(sgx_get_epc_virt_addr(page));
if (WARN_ONCE(ret, EREMOVE_ERROR_MESSAGE, ret, ret))
diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index a75eb44022a3..9a32bf5a1070 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -113,6 +113,9 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs)
encl->attributes = secs->attributes;
encl->attributes_mask = SGX_ATTR_UNPRIV_MASK;

+ sgx_record_epc_page(encl->secs.epc_page,
+ SGX_EPC_PAGE_UNRECLAIMABLE);
+
/* Set only after completion, as encl->lock has not been taken. */
set_bit(SGX_ENCL_CREATED, &encl->flags);

@@ -322,7 +325,7 @@ static int sgx_encl_add_page(struct sgx_encl *encl, unsigned long src,
goto err_out;
}

- sgx_record_epc_page(epc_page, SGX_EPC_PAGE_RECLAIMER_TRACKED);
+ sgx_record_epc_page(epc_page, SGX_EPC_PAGE_RECLAIMABLE);
mutex_unlock(&encl->lock);
mmap_read_unlock(current->mm);
return ret;
@@ -976,7 +979,7 @@ static long sgx_enclave_modify_types(struct sgx_encl *encl,

mutex_lock(&encl->lock);

- sgx_record_epc_page(entry->epc_page, SGX_EPC_PAGE_RECLAIMER_TRACKED);
+ sgx_record_epc_page(entry->epc_page, SGX_EPC_PAGE_RECLAIMABLE);
}

/* Change EPC type */
diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index dec1d57cbff6..b26860399402 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -318,7 +318,7 @@ static void sgx_reclaim_pages(void)
/* The owner is freeing the page. No need to add the
* page back to the list of reclaimable pages.
*/
- epc_page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
+ sgx_epc_page_reset_state(epc_page);
}
spin_unlock(&sgx_global_lru.lock);

@@ -344,6 +344,7 @@ static void sgx_reclaim_pages(void)

skip:
spin_lock(&sgx_global_lru.lock);
+ sgx_epc_page_set_state(epc_page, SGX_EPC_PAGE_RECLAIMABLE);
list_add_tail(&epc_page->list, &sgx_global_lru.reclaimable);
spin_unlock(&sgx_global_lru.lock);

@@ -367,7 +368,7 @@ static void sgx_reclaim_pages(void)
sgx_reclaimer_write(epc_page, &backing[i]);

kref_put(&encl_page->encl->refcount, sgx_encl_release);
- epc_page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
+ sgx_epc_page_reset_state(epc_page);

sgx_free_epc_page(epc_page);
}
@@ -507,9 +508,9 @@ struct sgx_epc_page *__sgx_alloc_epc_page(void)
void sgx_record_epc_page(struct sgx_epc_page *page, unsigned long flags)
{
spin_lock(&sgx_global_lru.lock);
- WARN_ON_ONCE(page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED);
+ WARN_ON_ONCE(sgx_epc_page_reclaimable(page->flags));
page->flags |= flags;
- if (flags & SGX_EPC_PAGE_RECLAIMER_TRACKED)
+ if (sgx_epc_page_reclaimable(flags))
list_add_tail(&page->list, &sgx_global_lru.reclaimable);
spin_unlock(&sgx_global_lru.lock);
}
@@ -527,7 +528,7 @@ void sgx_record_epc_page(struct sgx_epc_page *page, unsigned long flags)
int sgx_drop_epc_page(struct sgx_epc_page *page)
{
spin_lock(&sgx_global_lru.lock);
- if (page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED) {
+ if (sgx_epc_page_reclaimable(page->flags)) {
/* The page is being reclaimed. */
if (list_empty(&page->list)) {
spin_unlock(&sgx_global_lru.lock);
@@ -535,7 +536,7 @@ int sgx_drop_epc_page(struct sgx_epc_page *page)
}

list_del(&page->list);
- page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
+ sgx_epc_page_reset_state(page);
}
spin_unlock(&sgx_global_lru.lock);

@@ -607,6 +608,8 @@ void sgx_free_epc_page(struct sgx_epc_page *page)
struct sgx_epc_section *section = &sgx_epc_sections[page->section];
struct sgx_numa_node *node = section->node;

+ WARN_ON_ONCE(page->flags & (SGX_EPC_PAGE_STATE_MASK));
+
spin_lock(&node->lock);

page->owner = NULL;
@@ -614,7 +617,7 @@ void sgx_free_epc_page(struct sgx_epc_page *page)
list_add(&page->list, &node->sgx_poison_page_list);
else
list_add_tail(&page->list, &node->free_page_list);
- page->flags = SGX_EPC_PAGE_IS_FREE;
+ page->flags = SGX_EPC_PAGE_FREE;

spin_unlock(&node->lock);
atomic_long_inc(&sgx_nr_free_pages);
@@ -715,7 +718,7 @@ int arch_memory_failure(unsigned long pfn, int flags)
* If the page is on a free list, move it to the per-node
* poison page list.
*/
- if (page->flags & SGX_EPC_PAGE_IS_FREE) {
+ if (page->flags == SGX_EPC_PAGE_FREE) {
list_move(&page->list, &node->sgx_poison_page_list);
goto out;
}
diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index 113d930fd087..2faeb40b345f 100644
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -23,11 +23,36 @@
#define SGX_NR_LOW_PAGES 32
#define SGX_NR_HIGH_PAGES 64

-/* Pages, which are being tracked by the page reclaimer. */
-#define SGX_EPC_PAGE_RECLAIMER_TRACKED BIT(0)
+enum sgx_epc_page_state {
+ /* Not tracked by the reclaimer:
+ * Pages allocated for virtual EPC which are never tracked by the host
+ * reclaimer; pages just allocated from free list but not yet put in
+ * use; pages just reclaimed, but not yet returned to the free list.
+ * Becomes FREE after sgx_free_epc()
+ * Becomes RECLAIMABLE or UNRECLAIMABLE after sgx_record_epc()
+ */
+ SGX_EPC_PAGE_NOT_TRACKED = 0,
+
+ /* Page is in the free list, ready for allocation
+ * Becomes NOT_TRACKED after sgx_alloc_epc_page()
+ */
+ SGX_EPC_PAGE_FREE = 1,
+
+ /* Page is in use and tracked in a reclaimable LRU list
+ * Becomes NOT_TRACKED after sgx_drop_epc()
+ */
+ SGX_EPC_PAGE_RECLAIMABLE = 2,
+
+ /* Page is in use but tracked in an unreclaimable LRU list. These are
+ * only reclaimable when the whole enclave is OOM killed or the enclave
+ * is released, e.g., VA, SECS pages
+ * Becomes NOT_TRACKED after sgx_drop_epc()
+ */
+ SGX_EPC_PAGE_UNRECLAIMABLE = 3,

-/* Pages on free list */
-#define SGX_EPC_PAGE_IS_FREE BIT(1)
+};
+
+#define SGX_EPC_PAGE_STATE_MASK GENMASK(2, 0)

struct sgx_epc_page {
unsigned int section;
@@ -37,6 +62,22 @@ struct sgx_epc_page {
struct list_head list;
};

+static inline void sgx_epc_page_reset_state(struct sgx_epc_page *page)
+{
+ page->flags &= ~SGX_EPC_PAGE_STATE_MASK;
+}
+
+static inline void sgx_epc_page_set_state(struct sgx_epc_page *page, unsigned long flags)
+{
+ page->flags &= ~SGX_EPC_PAGE_STATE_MASK;
+ page->flags |= (flags & SGX_EPC_PAGE_STATE_MASK);
+}
+
+static inline bool sgx_epc_page_reclaimable(unsigned long flags)
+{
+ return SGX_EPC_PAGE_RECLAIMABLE == (flags & SGX_EPC_PAGE_STATE_MASK);
+}
+
/*
* Contains the tracking data for NUMA nodes having EPC pages. Most importantly,
* the free page list local to the node is stored here.
--
2.25.1