From mboxrd@z Thu Jan 1 00:00:00 1970 From: Haitao Huang Subject: [PATCH v4 07/18] x86/sgx: Introduce RECLAIM_IN_PROGRESS state Date: Tue, 12 Sep 2023 21:06:24 -0700 Message-ID: <20230913040635.28815-8-haitao.huang@linux.intel.com> References: <20230913040635.28815-1-haitao.huang@linux.intel.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1694578131; x=1726114131; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=+xSYj6fZGa/PyizPvcdrnkHmA+dx7qyQbKvuOsVcq/Y=; b=aA7vQOpsIIaZWUTvg6TkGN4/djcRA3iaytdyEhUesBS+rbiBmy480UZ4 2HIT/L0IcJGgL7e/vuHfWmcHSW7++kgE4QPpXEi0YTc3BV5ebedHrWgxx 21g05KoH3Yryzj+QjalN8dyRINmlPAhGcdJ+y15t/1uUTse/EX90STjQS j1iP02g73nihf4MqHsAVM32lNouFhzCMT1AC1a1t9HVjOrseQa1H53sEh StE7sReoyhktlZIFiun7hs5ultmvTbO3u1o9+5zNU8XNoryCy6DJkG60F uc/y/VJxNeZz9lemjKrcJBPBBv4/IrPfUqAk+SN9rekmesW1KmehMQrjk A==; In-Reply-To: <20230913040635.28815-1-haitao.huang-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii" To: jarkko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, dave.hansen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-sgx-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org, hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org, sohil.mehta-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org Cc: zhiquan1.li-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, kristen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, seanjc-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, zhanb-0li6OtcxBFHby3iVrkZq2A@public.gmane.org, anakrish-0li6OtcxBFHby3iVrkZq2A@public.gmane.org, mikko.ylinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, yangjie-0li6OtcxBFHby3iVrkZq2A@public.gmane.org From: Sean Christopherson Add RECLAIM_IN_PROGRESS state to not rely on list_empty(&epc_page->list) to determine if an EPC page is selected as a reclaiming candidate. When a page is being reclaimed from the page pool (sgx_global_lru), there is an intermediate stage where a page may have been identified as a candidate for reclaiming, but has not yet been reclaimed. Currently such pages are list_del_init()'d from the global LRU list, and stored in a an array on stack. To prevent another thread from dropping the same page in the middle of reclaiming, sgx_drop_epc_page() checks for list_empty(&epc_page->list). A later patch will replace the array on stack with a temporary list to store the candidate pages, so list_empty() should no longer be used for this purpose. Signed-off-by: Sean Christopherson Signed-off-by: Kristen Carlson Accardi Signed-off-by: Haitao Huang Cc: Sean Christopherson --- V4: - Fixed some typos. - Revised commit message. V3: - Extend the sgx_epc_page_state enum introduced earlier to replace the flag based approach. --- arch/x86/kernel/cpu/sgx/main.c | 21 ++++++++++----------- arch/x86/kernel/cpu/sgx/sgx.h | 16 ++++++++++++++++ 2 files changed, 26 insertions(+), 11 deletions(-) diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c index b26860399402..c1ae19a154d0 100644 --- a/arch/x86/kernel/cpu/sgx/main.c +++ b/arch/x86/kernel/cpu/sgx/main.c @@ -312,13 +312,15 @@ static void sgx_reclaim_pages(void) list_del_init(&epc_page->list); encl_page = epc_page->owner; - if (kref_get_unless_zero(&encl_page->encl->refcount) != 0) + 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; - else + } else { /* The owner is freeing the page. No need to add the * page back to the list of reclaimable pages. */ sgx_epc_page_reset_state(epc_page); + } } spin_unlock(&sgx_global_lru.lock); @@ -528,16 +530,13 @@ 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 (sgx_epc_page_reclaimable(page->flags)) { - /* The page is being reclaimed. */ - if (list_empty(&page->list)) { - spin_unlock(&sgx_global_lru.lock); - return -EBUSY; - } - - list_del(&page->list); - sgx_epc_page_reset_state(page); + if (sgx_epc_page_reclaim_in_progress(page->flags)) { + spin_unlock(&sgx_global_lru.lock); + return -EBUSY; } + + list_del(&page->list); + sgx_epc_page_reset_state(page); spin_unlock(&sgx_global_lru.lock); return 0; diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h index 2faeb40b345f..764cec23f4e5 100644 --- a/arch/x86/kernel/cpu/sgx/sgx.h +++ b/arch/x86/kernel/cpu/sgx/sgx.h @@ -40,6 +40,8 @@ enum sgx_epc_page_state { /* Page is in use and tracked in a reclaimable LRU list * Becomes NOT_TRACKED after sgx_drop_epc() + * Becomes RECLAIM_IN_PROGRESS in sgx_reclaim_pages() when identified + * for reclaiming */ SGX_EPC_PAGE_RECLAIMABLE = 2, @@ -50,6 +52,14 @@ enum sgx_epc_page_state { */ SGX_EPC_PAGE_UNRECLAIMABLE = 3, + /* Page is being prepared for reclamation, tracked in a temporary + * isolated list by the reclaimer. + * Changes in sgx_reclaim_pages() back to RECLAIMABLE if preparation + * fails for any reason. + * Becomes NOT_TRACKED if reclaimed successfully in sgx_reclaim_pages() + * and immediately sgx_free_epc() is called to make it FREE. + */ + SGX_EPC_PAGE_RECLAIM_IN_PROGRESS = 4, }; #define SGX_EPC_PAGE_STATE_MASK GENMASK(2, 0) @@ -73,6 +83,12 @@ static inline void sgx_epc_page_set_state(struct sgx_epc_page *page, unsigned lo page->flags |= (flags & SGX_EPC_PAGE_STATE_MASK); } +static inline bool sgx_epc_page_reclaim_in_progress(unsigned long flags) +{ + return SGX_EPC_PAGE_RECLAIM_IN_PROGRESS == (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); -- 2.25.1