linux-kernel - [PATCH v7 06/15] x86/sgx: Abstract tracking reclaimable pages in LRU

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Date: Mon, 22 Jan 2024 09:20:39 -0800
From: Haitao Huang <haitao.huang@...ux.intel.com>
To: jarkko@...nel.org,
	dave.hansen@...ux.intel.com,
	tj@...nel.org,
	mkoutny@...e.com,
	linux-kernel@...r.kernel.org,
	linux-sgx@...r.kernel.org,
	x86@...nel.org,
	cgroups@...r.kernel.org,
	tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	hpa@...or.com,
	sohil.mehta@...el.com
Cc: zhiquan1.li@...el.com,
	kristen@...ux.intel.com,
	seanjc@...gle.com,
	zhanb@...rosoft.com,
	anakrish@...rosoft.com,
	mikko.ylinen@...ux.intel.com,
	yangjie@...rosoft.com
Subject: [PATCH v7 06/15] x86/sgx: Abstract tracking reclaimable pages in LRU

From: Kristen Carlson Accardi <kristen@...ux.intel.com>

The functions, sgx_{mark,unmark}_page_reclaimable(), manage the tracking
of reclaimable EPC pages: sgx_mark_page_reclaimable() adds a newly
allocated page into the global LRU list while
sgx_unmark_page_reclaimable() does the opposite. Abstract the hard coded
global LRU references in these functions to make them reusable when
pages are tracked in per-cgroup LRUs.

Create a helper, sgx_lru_list(), that returns the LRU that tracks a given
EPC page. It simply returns the global LRU now, and will later return
the LRU of the cgroup within which the EPC page was allocated. Replace
the hard coded global LRU with a call to this helper.

Next patches will first get the cgroup reclamation flow ready while
keeping pages tracked in the global LRU and reclaimed by ksgxd before we
make the switch in the end for sgx_lru_list() to return per-cgroup
LRU.

Co-developed-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
Co-developed-by: Haitao Huang <haitao.huang@...ux.intel.com>
Signed-off-by: Haitao Huang <haitao.huang@...ux.intel.com>
---
V7:
- Split this out from the big patch, #10 in V6. (Dave, Kai)
---
 arch/x86/kernel/cpu/sgx/main.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 912959c7ecc9..cde750688e62 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -32,6 +32,11 @@ static DEFINE_XARRAY(sgx_epc_address_space);
  */
 static struct sgx_epc_lru_list sgx_global_lru;
 
+static inline struct sgx_epc_lru_list *sgx_lru_list(struct sgx_epc_page *epc_page)
+{
+	return &sgx_global_lru;
+}
+
 static atomic_long_t sgx_nr_free_pages = ATOMIC_LONG_INIT(0);
 
 /* Nodes with one or more EPC sections. */
@@ -500,25 +505,25 @@ struct sgx_epc_page *__sgx_alloc_epc_page(void)
 }
 
 /**
- * sgx_mark_page_reclaimable() - Mark a page as reclaimable
+ * sgx_mark_page_reclaimable() - Mark a page as reclaimable and add it to an appropriate LRU
  * @page:	EPC page
  *
- * Mark a page as reclaimable and add it to the active page list. Pages
- * are automatically removed from the active list when freed.
  */
 void sgx_mark_page_reclaimable(struct sgx_epc_page *page)
 {
-	spin_lock(&sgx_global_lru.lock);
+	struct sgx_epc_lru_list *lru = sgx_lru_list(page);
+
+	spin_lock(&lru->lock);
 	page->flags |= SGX_EPC_PAGE_RECLAIMER_TRACKED;
-	list_add_tail(&page->list, &sgx_global_lru.reclaimable);
-	spin_unlock(&sgx_global_lru.lock);
+	list_add_tail(&page->list, &lru->reclaimable);
+	spin_unlock(&lru->lock);
 }
 
 /**
  * sgx_unmark_page_reclaimable() - Remove a page from the reclaim list
  * @page:	EPC page
  *
- * Clear the reclaimable flag and remove the page from the active page list.
+ * Clear the reclaimable flag if set and remove the page from its LRU.
  *
  * Return:
  *   0 on success,
@@ -526,18 +531,20 @@ void sgx_mark_page_reclaimable(struct sgx_epc_page *page)
  */
 int sgx_unmark_page_reclaimable(struct sgx_epc_page *page)
 {
-	spin_lock(&sgx_global_lru.lock);
+	struct sgx_epc_lru_list *lru = sgx_lru_list(page);
+
+	spin_lock(&lru->lock);
 	if (page->flags & SGX_EPC_PAGE_RECLAIMER_TRACKED) {
 		/* The page is being reclaimed. */
 		if (list_empty(&page->list)) {
-			spin_unlock(&sgx_global_lru.lock);
+			spin_unlock(&lru->lock);
 			return -EBUSY;
 		}
 
 		list_del(&page->list);
 		page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;
 	}
-	spin_unlock(&sgx_global_lru.lock);
+	spin_unlock(&lru->lock);
 
 	return 0;
 }
-- 
2.25.1