Re: [PATCH v4 04/18] x86/sgx: Use sgx_epc_lru_lists for existing active page list

Jarkko Sakkinen
2023-09-13T15:00:54Z

On Wed Sep 13, 2023 at 7:06 AM EEST, Haitao Huang wrote:
> From: Kristen Carlson Accardi <kristen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
>
> All EPC pages of enclaves including VA and SECS will be tracked in

s/VA/Version Array (VA)/
s/SECS/SGX Enclave Control Structure (SECS)/

Just a nitpick, because it is always good to remind what these acronyms
are (there are so many of them in this world).

> sgx_epc_lru_lists structs, one per cgroup. For now just replace the
> existing sgx_active_page_list in the reclaimer and its spinlock with a
> global sgx_epc_lru_lists struct. VA and SECS pages are still not tracked
> at this point but they will be tracked after an unreclaimable LRU list
> is added to the sgx_epc_lru_lists struct.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Signed-off-by: Kristen Carlson Accardi <kristen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> Signed-off-by: Haitao Huang <haitao.huang-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> Cc: Sean Christopherson <seanjc-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
> ---
> V4:
> - No change, only reordered the patch.
>
> V3:
> - Remove usage of list wrapper
> ---
> arch/x86/kernel/cpu/sgx/main.c | 39 +++++++++++++++++-----------------
> 1 file changed, 20 insertions(+), 19 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index 166692f2d501..afce51d6e94a 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);
>
> @@ -304,13 +303,13 @@ 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 = list_first_entry_or_null(&sgx_global_lru.reclaimable,
> + struct sgx_epc_page, list);
> + 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->owner;
>
> @@ -322,7 +321,7 @@ 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];
> @@ -345,9 +344,9 @@ 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);
> + list_add_tail(&epc_page->list, &sgx_global_lru.reclaimable);
> + spin_unlock(&sgx_global_lru.lock);
>
> kref_put(&encl_page->encl->refcount, sgx_encl_release);
>
> @@ -378,7 +377,7 @@ 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);
> }
>
> /*
> @@ -430,6 +429,8 @@ static bool __init sgx_page_reclaimer_init(void)
>
> ksgxd_tsk = tsk;
>
> + sgx_lru_init(&sgx_global_lru);
> +
> return true;
> }
>
> @@ -505,10 +506,10 @@ 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);
> + list_add_tail(&page->list, &sgx_global_lru.reclaimable);
> + spin_unlock(&sgx_global_lru.lock);
> }
>
> /**
> @@ -523,18 +524,18 @@ 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;
> }
> @@ -567,7 +568,7 @@ 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) {
> --
> 2.25.1

Other than that looks good to me (including the commit description).

BR, Jarkko