diff mbox series

[v6,08/12] x86/sgx: Use a list to track to-be-reclaimed pages

Message ID 20231030182013.40086-9-haitao.huang@linux.intel.com
State New
Headers
Series Add Cgroup support for SGX EPC memory |

Commit Message

Haitao Huang Oct. 30, 2023, 6:20 p.m. UTC 
  From: Sean Christopherson <sean.j.christopherson@intel.com>

Change sgx_reclaim_pages() to use a list rather than an array for
storing the epc_pages which will be reclaimed. This change is needed
to transition to the LRU implementation for EPC cgroup support.

When the EPC cgroup is implemented, the reclaiming process will do a
pre-order tree walk for the subtree starting from the limit-violating
cgroup.  When each node is visited, candidate pages are selected from
its "reclaimable" LRU list and moved into this temporary list. Passing a
list from node to node for temporary storage in this walk is more
straightforward than using an array.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Co-developed-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Co-developed-by: Haitao Huang<haitao.huang@linux.intel.com>
Signed-off-by: Haitao Huang<haitao.huang@linux.intel.com>
Cc: Sean Christopherson <seanjc@google.com>
---
V6:
- Remove extra list_del_init and style fix (Kai)

V4:
- Changes needed for patch reordering
- Revised commit message

V3:
- Removed list wrappers
---
 arch/x86/kernel/cpu/sgx/main.c | 35 +++++++++++++++-------------------
 1 file changed, 15 insertions(+), 20 deletions(-)

Comments

Jarkko Sakkinen Nov. 15, 2023, 8:59 p.m. UTC | #1 
On Mon Oct 30, 2023 at 8:20 PM EET, Haitao Huang wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
>
> Change sgx_reclaim_pages() to use a list rather than an array for
> storing the epc_pages which will be reclaimed. This change is needed
> to transition to the LRU implementation for EPC cgroup support.
>
> When the EPC cgroup is implemented, the reclaiming process will do a
> pre-order tree walk for the subtree starting from the limit-violating
> cgroup.  When each node is visited, candidate pages are selected from
> its "reclaimable" LRU list and moved into this temporary list. Passing a
> list from node to node for temporary storage in this walk is more
> straightforward than using an array.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Co-developed-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> Co-developed-by: Haitao Huang<haitao.huang@linux.intel.com>
> Signed-off-by: Haitao Huang<haitao.huang@linux.intel.com>
> Cc: Sean Christopherson <seanjc@google.com>
> ---
> V6:
> - Remove extra list_del_init and style fix (Kai)
>
> V4:
> - Changes needed for patch reordering
> - Revised commit message
>
> V3:
> - Removed list wrappers
> ---
>  arch/x86/kernel/cpu/sgx/main.c | 35 +++++++++++++++-------------------
>  1 file changed, 15 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index e27ac73d8843..33bcba313d40 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -296,12 +296,11 @@ static void sgx_reclaimer_write(struct sgx_epc_page *epc_page,
>   */
>  static void sgx_reclaim_pages(void)
>  {
> -	struct sgx_epc_page *chunk[SGX_NR_TO_SCAN];
>  	struct sgx_backing backing[SGX_NR_TO_SCAN];
> +	struct sgx_epc_page *epc_page, *tmp;
>  	struct sgx_encl_page *encl_page;
> -	struct sgx_epc_page *epc_page;
>  	pgoff_t page_index;
> -	int cnt = 0;
> +	LIST_HEAD(iso);
>  	int ret;
>  	int i;
>  
> @@ -317,7 +316,7 @@ static void sgx_reclaim_pages(void)
>  
>  		if (kref_get_unless_zero(&encl_page->encl->refcount) != 0) {
>  			sgx_epc_page_set_state(epc_page, SGX_EPC_PAGE_RECLAIM_IN_PROGRESS);
> -			chunk[cnt++] = epc_page;
> +			list_move_tail(&epc_page->list, &iso);
>  		} else
>  			/* The owner is freeing the page. No need to add the
>  			 * page back to the list of reclaimable pages.
> @@ -326,8 +325,11 @@ static void sgx_reclaim_pages(void)
>  	}
>  	spin_unlock(&sgx_global_lru.lock);
>  
> -	for (i = 0; i < cnt; i++) {
> -		epc_page = chunk[i];
> +	if (list_empty(&iso))
> +		return;
> +
> +	i = 0;
> +	list_for_each_entry_safe(epc_page, tmp, &iso, list) {
>  		encl_page = epc_page->owner;
>  
>  		if (!sgx_reclaimer_age(epc_page))
> @@ -342,6 +344,7 @@ static void sgx_reclaim_pages(void)
>  			goto skip;
>  		}
>  
> +		i++;
>  		encl_page->desc |= SGX_ENCL_PAGE_BEING_RECLAIMED;
>  		mutex_unlock(&encl_page->encl->lock);
>  		continue;
> @@ -349,27 +352,19 @@ 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);
> +		list_move_tail(&epc_page->list, &sgx_global_lru.reclaimable);
>  		spin_unlock(&sgx_global_lru.lock);
>  
>  		kref_put(&encl_page->encl->refcount, sgx_encl_release);
> -
> -		chunk[i] = NULL;
> -	}
> -
> -	for (i = 0; i < cnt; i++) {
> -		epc_page = chunk[i];
> -		if (epc_page)
> -			sgx_reclaimer_block(epc_page);
>  	}
>  
> -	for (i = 0; i < cnt; i++) {
> -		epc_page = chunk[i];
> -		if (!epc_page)
> -			continue;
> +	list_for_each_entry(epc_page, &iso, list)
> +		sgx_reclaimer_block(epc_page);
>  
> +	i = 0;
> +	list_for_each_entry_safe(epc_page, tmp, &iso, list) {
>  		encl_page = epc_page->owner;
> -		sgx_reclaimer_write(epc_page, &backing[i]);
> +		sgx_reclaimer_write(epc_page, &backing[i++]);

Couldn't you alternatively "&backing[--i]" and not reset i to zero
before the loop?

>  
>  		kref_put(&encl_page->encl->refcount, sgx_encl_release);
>  		sgx_epc_page_reset_state(epc_page);

BR, Jarkko
diff mbox series

Patch

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index e27ac73d8843..33bcba313d40 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -296,12 +296,11 @@  static void sgx_reclaimer_write(struct sgx_epc_page *epc_page,
  */
 static void sgx_reclaim_pages(void)
 {
-	struct sgx_epc_page *chunk[SGX_NR_TO_SCAN];
 	struct sgx_backing backing[SGX_NR_TO_SCAN];
+	struct sgx_epc_page *epc_page, *tmp;
 	struct sgx_encl_page *encl_page;
-	struct sgx_epc_page *epc_page;
 	pgoff_t page_index;
-	int cnt = 0;
+	LIST_HEAD(iso);
 	int ret;
 	int i;
 
@@ -317,7 +316,7 @@  static void sgx_reclaim_pages(void)
 
 		if (kref_get_unless_zero(&encl_page->encl->refcount) != 0) {
 			sgx_epc_page_set_state(epc_page, SGX_EPC_PAGE_RECLAIM_IN_PROGRESS);
-			chunk[cnt++] = epc_page;
+			list_move_tail(&epc_page->list, &iso);
 		} else
 			/* The owner is freeing the page. No need to add the
 			 * page back to the list of reclaimable pages.
@@ -326,8 +325,11 @@  static void sgx_reclaim_pages(void)
 	}
 	spin_unlock(&sgx_global_lru.lock);
 
-	for (i = 0; i < cnt; i++) {
-		epc_page = chunk[i];
+	if (list_empty(&iso))
+		return;
+
+	i = 0;
+	list_for_each_entry_safe(epc_page, tmp, &iso, list) {
 		encl_page = epc_page->owner;
 
 		if (!sgx_reclaimer_age(epc_page))
@@ -342,6 +344,7 @@  static void sgx_reclaim_pages(void)
 			goto skip;
 		}
 
+		i++;
 		encl_page->desc |= SGX_ENCL_PAGE_BEING_RECLAIMED;
 		mutex_unlock(&encl_page->encl->lock);
 		continue;
@@ -349,27 +352,19 @@  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);
+		list_move_tail(&epc_page->list, &sgx_global_lru.reclaimable);
 		spin_unlock(&sgx_global_lru.lock);
 
 		kref_put(&encl_page->encl->refcount, sgx_encl_release);
-
-		chunk[i] = NULL;
-	}
-
-	for (i = 0; i < cnt; i++) {
-		epc_page = chunk[i];
-		if (epc_page)
-			sgx_reclaimer_block(epc_page);
 	}
 
-	for (i = 0; i < cnt; i++) {
-		epc_page = chunk[i];
-		if (!epc_page)
-			continue;
+	list_for_each_entry(epc_page, &iso, list)
+		sgx_reclaimer_block(epc_page);
 
+	i = 0;
+	list_for_each_entry_safe(epc_page, tmp, &iso, list) {
 		encl_page = epc_page->owner;
-		sgx_reclaimer_write(epc_page, &backing[i]);
+		sgx_reclaimer_write(epc_page, &backing[i++]);
 
 		kref_put(&encl_page->encl->refcount, sgx_encl_release);
 		sgx_epc_page_reset_state(epc_page);