diff mbox series

[v2,04/18] x86/sgx: Use sgx_epc_lru_lists for existing active page list

Message ID 20221202183655.3767674-5-kristen@linux.intel.com
State New
Headers
Series Add Cgroup support for SGX EPC memory |

Commit Message

Kristen Carlson Accardi Dec. 2, 2022, 6:36 p.m. UTC 
  Replace the existing sgx_active_page_list and its spinlock with
a global sgx_epc_lru_lists struct.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Cc: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kernel/cpu/sgx/main.c | 39 +++++++++++++++++-----------------
 1 file changed, 19 insertions(+), 20 deletions(-)

Comments

Dave Hansen Dec. 2, 2022, 9:43 p.m. UTC | #1 
On 12/2/22 10:36, Kristen Carlson Accardi wrote:
> +	spin_lock(&sgx_global_lru.lock);
>  	for (i = 0; i < SGX_NR_TO_SCAN; i++) {
> -		if (list_empty(&sgx_active_page_list))
> +		epc_page = sgx_epc_pop_reclaimable(&sgx_global_lru);
> +		if (!epc_page)
>  			break;

One other nit about the structure of the patches: This introduced *both*
reclaimable and unreclaimable list_heads.  But, it has zero use for the
unreclaimable ones during the refactoring here.  I probably would have
left out the 'unreclaimable' bits for now.

BTW, this is a nice sign:

>  arch/x86/kernel/cpu/sgx/main.c | 39 +++++++++++++++++-----------------
>  1 file changed, 19 insertions(+), 20 deletions(-)
Kristen Carlson Accardi Dec. 2, 2022, 9:51 p.m. UTC | #2 
On Fri, 2022-12-02 at 13:43 -0800, Dave Hansen wrote:
> On 12/2/22 10:36, Kristen Carlson Accardi wrote:
> > +       spin_lock(&sgx_global_lru.lock);
> >         for (i = 0; i < SGX_NR_TO_SCAN; i++) {
> > -               if (list_empty(&sgx_active_page_list))
> > +               epc_page =
> > sgx_epc_pop_reclaimable(&sgx_global_lru);
> > +               if (!epc_page)
> >                         break;
> 
> One other nit about the structure of the patches: This introduced
> *both*
> reclaimable and unreclaimable list_heads.  But, it has zero use for
> the
> unreclaimable ones during the refactoring here.  I probably would
> have
> left out the 'unreclaimable' bits for now.

I know - and originally the addition of unreclaimable was added later,
but when I posted the RFC I felt there was some misunderstanding about
what this data structure was and how it would be used because the
addition of the unreclaimable bits came later. So I stuck both lists in
one so it'd be a better view of what the data structure would look
like.

> 
> BTW, this is a nice sign:
> 
> >  arch/x86/kernel/cpu/sgx/main.c | 39 +++++++++++++++++-------------
> > ----
> >  1 file changed, 19 insertions(+), 20 deletions(-)
> 
>
Dave Hansen Dec. 2, 2022, 10:10 p.m. UTC | #3 
On 12/2/22 13:51, Kristen Carlson Accardi wrote:
> I know - and originally the addition of unreclaimable was added later,
> but when I posted the RFC I felt there was some misunderstanding about
> what this data structure was and how it would be used because the
> addition of the unreclaimable bits came later. So I stuck both lists in
> one so it'd be a better view of what the data structure would look
> like.

You're not insane for thinking that.

But, it's really OK to introduce an abstraction that *looks* silly on
its face at first.  You can easily just make up for it by saying:

	struct silly_abstraction {
		struct list_head list;
	}

	Oh, boy does my structure look silly.  It's a structure with a
	single list_head.  Why oh why would I do something silly like
	that?  Well, for now, the code has but one list.  Soon, I'll
	add a whole smorgasbord of lists.  Bear with me for now.
diff mbox series

Patch

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index ffce6fc70a1f..447cf4b8580c 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -26,10 +26,9 @@  static DEFINE_XARRAY(sgx_epc_address_space);
 
 /*
  * These variables are part of the state of the reclaimer, and must be accessed
- * with sgx_reclaimer_lock acquired.
+ * with sgx_global_lru.lock acquired.
  */
-static LIST_HEAD(sgx_active_page_list);
-static DEFINE_SPINLOCK(sgx_reclaimer_lock);
+static struct sgx_epc_lru_lists sgx_global_lru;
 
 static atomic_long_t sgx_nr_free_pages = ATOMIC_LONG_INIT(0);
 
@@ -298,14 +297,12 @@  static void __sgx_reclaim_pages(void)
 	int ret;
 	int i;
 
-	spin_lock(&sgx_reclaimer_lock);
+	spin_lock(&sgx_global_lru.lock);
 	for (i = 0; i < SGX_NR_TO_SCAN; i++) {
-		if (list_empty(&sgx_active_page_list))
+		epc_page = sgx_epc_pop_reclaimable(&sgx_global_lru);
+		if (!epc_page)
 			break;
 
-		epc_page = list_first_entry(&sgx_active_page_list,
-					    struct sgx_epc_page, list);
-		list_del_init(&epc_page->list);
 		encl_page = epc_page->encl_owner;
 
 		if (kref_get_unless_zero(&encl_page->encl->refcount) != 0)
@@ -316,7 +313,7 @@  static void __sgx_reclaim_pages(void)
 			 */
 			epc_page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
 	}
-	spin_unlock(&sgx_reclaimer_lock);
+	spin_unlock(&sgx_global_lru.lock);
 
 	for (i = 0; i < cnt; i++) {
 		epc_page = chunk[i];
@@ -339,9 +336,9 @@  static void __sgx_reclaim_pages(void)
 		continue;
 
 skip:
-		spin_lock(&sgx_reclaimer_lock);
-		list_add_tail(&epc_page->list, &sgx_active_page_list);
-		spin_unlock(&sgx_reclaimer_lock);
+		spin_lock(&sgx_global_lru.lock);
+		sgx_epc_push_reclaimable(&sgx_global_lru, epc_page);
+		spin_unlock(&sgx_global_lru.lock);
 
 		kref_put(&encl_page->encl->refcount, sgx_encl_release);
 
@@ -378,7 +375,7 @@  static void sgx_reclaim_pages(void)
 static bool sgx_should_reclaim(unsigned long watermark)
 {
 	return atomic_long_read(&sgx_nr_free_pages) < watermark &&
-	       !list_empty(&sgx_active_page_list);
+	       !list_empty(&sgx_global_lru.reclaimable);
 }
 
 /*
@@ -433,6 +430,8 @@  static bool __init sgx_page_reclaimer_init(void)
 
 	ksgxd_tsk = tsk;
 
+	sgx_lru_init(&sgx_global_lru);
+
 	return true;
 }
 
@@ -508,10 +507,10 @@  struct sgx_epc_page *__sgx_alloc_epc_page(void)
  */
 void sgx_mark_page_reclaimable(struct sgx_epc_page *page)
 {
-	spin_lock(&sgx_reclaimer_lock);
+	spin_lock(&sgx_global_lru.lock);
 	page->flags |= SGX_EPC_PAGE_RECLAIMER_TRACKED;
-	list_add_tail(&page->list, &sgx_active_page_list);
-	spin_unlock(&sgx_reclaimer_lock);
+	sgx_epc_push_reclaimable(&sgx_global_lru, page);
+	spin_unlock(&sgx_global_lru.lock);
 }
 
 /**
@@ -526,18 +525,18 @@  void sgx_mark_page_reclaimable(struct sgx_epc_page *page)
  */
 int sgx_unmark_page_reclaimable(struct sgx_epc_page *page)
 {
-	spin_lock(&sgx_reclaimer_lock);
+	spin_lock(&sgx_global_lru.lock);
 	if (page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED) {
 		/* The page is being reclaimed. */
 		if (list_empty(&page->list)) {
-			spin_unlock(&sgx_reclaimer_lock);
+			spin_unlock(&sgx_global_lru.lock);
 			return -EBUSY;
 		}
 
 		list_del(&page->list);
 		page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
 	}
-	spin_unlock(&sgx_reclaimer_lock);
+	spin_unlock(&sgx_global_lru.lock);
 
 	return 0;
 }
@@ -574,7 +573,7 @@  struct sgx_epc_page *sgx_alloc_epc_page(void *owner, bool reclaim)
 			break;
 		}
 
-		if (list_empty(&sgx_active_page_list))
+		if (list_empty(&sgx_global_lru.reclaimable))
 			return ERR_PTR(-ENOMEM);
 
 		if (!reclaim) {