From patchwork Thu Feb 6 16:18:48 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steve Capper X-Patchwork-Id: 3596891 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 5377FBF418 for ; Thu, 6 Feb 2014 16:20:10 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 483502012B for ; Thu, 6 Feb 2014 16:20:09 +0000 (UTC) Received: from casper.infradead.org (casper.infradead.org [85.118.1.10]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 36B2A20122 for ; Thu, 6 Feb 2014 16:20:07 +0000 (UTC) Received: from merlin.infradead.org ([2001:4978:20e::2]) by casper.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1WBRfy-0003Ss-Qf; Thu, 06 Feb 2014 16:19:42 +0000 Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1WBRfu-00044a-1i; Thu, 06 Feb 2014 16:19:38 +0000 Received: from mail-wg0-f51.google.com ([74.125.82.51]) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1WBRfh-00041r-Kf for linux-arm-kernel@lists.infradead.org; Thu, 06 Feb 2014 16:19:28 +0000 Received: by mail-wg0-f51.google.com with SMTP id z12so1415696wgg.18 for ; Thu, 06 Feb 2014 08:19:03 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=TdD8C/ZXviAblSVKVJaTMkQAiR07bVSJBPU27n+HSY4=; b=J2eZBG7+xBQukHhu99elHb+vuU6zQaneqp1NiE19KonnOBD71hqKZCV8o1rbH3vRue ONKJn8LcS1g90RGC12SZhnGXfYFr9hY4NNBRRqvkrXZnR1X6nBKk84oynWvdgRpeqgr4 fgNTP5rkMbbAZBbTwLf8uXb2v2o6dE4+C+40c2ojeQUut6RtYZOJBZfnmTPs/FrjGfxi VJ87fA8DJkb2JfWPd4gBQpcrhsima+zVzjXLmAIy5p7DFhYNF16+7Yo84JuCzcFhJXh1 7/aHviRPZIKuzO2Q7Ta1D3utrjyv9O99ZIN7hfBlXYB0e7FaGHKwf9z+dn7DBiJjwcMV lFQw== X-Gm-Message-State: ALoCoQnLrNcdof8Oj1hn97mQVawf3oYrvZz3EV59JxZQXpN/bZU70UBVO44wmJSP/fq+Rtvg9Vi9 X-Received: by 10.181.13.112 with SMTP id ex16mr32823wid.23.1391703542505; Thu, 06 Feb 2014 08:19:02 -0800 (PST) Received: from marmot.wormnet.eu (marmot.wormnet.eu. [188.246.204.87]) by mx.google.com with ESMTPSA id d6sm6170359wiz.4.2014.02.06.08.19.01 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 06 Feb 2014 08:19:02 -0800 (PST) From: Steve Capper To: linux-arm-kernel@lists.infradead.org Subject: [RFC PATCH V2 1/4] arm: mm: Enable HAVE_RCU_TABLE_FREE logic Date: Thu, 6 Feb 2014 16:18:48 +0000 Message-Id: <1391703531-12845-2-git-send-email-steve.capper@linaro.org> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1391703531-12845-1-git-send-email-steve.capper@linaro.org> References: <1391703531-12845-1-git-send-email-steve.capper@linaro.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20140206_111925_835662_28601FC0 X-CRM114-Status: GOOD ( 14.65 ) X-Spam-Score: -2.6 (--) Cc: zishen.lim@linaro.org, linux@arm.linux.org.uk, patches@linaro.org, michael.hudson@linaro.org, catalin.marinas@arm.com, will.deacon@arm.com, gary.robertson@linaro.org, Steve Capper , chanho61.park@samsung.com, christoffer.dall@linaro.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.7 required=5.0 tests=BAYES_00,KHOP_BIG_TO_CC, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP In order to implement fast_get_user_pages we need to ensure that the page table walker is protected from page table pages being freed from under it. One way to achieve this is to have the walker disable interrupts, and rely on IPIs from the TLB flushing code blocking before the page table pages are freed. On some ARM platforms we have hardware TLB invalidation, thus the TLB flushing code won't necessarily broadcast IPIs. Also spuriously broadcasting IPIs can hurt system performance if done too often. This problem has already been solved on PowerPC and Sparc by batching up page table pages belonging to more than one mm_user, then scheduling an rcu_sched callback to free the pages. If one were to disable interrupts, that would block the page table pages being freed. This logic has also been promoted to core code and is activated when one enables HAVE_RCU_TABLE_FREE. This patch enables HAVE_RCU_TABLE_FREE and incorporates it into the existing ARM TLB logic. Signed-off-by: Steve Capper --- arch/arm/Kconfig | 1 + arch/arm/include/asm/tlb.h | 38 ++++++++++++++++++++++++++++++++++++-- 2 files changed, 37 insertions(+), 2 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index c1f1a7e..e4a0e59 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -55,6 +55,7 @@ config ARM select HAVE_PERF_EVENTS select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP + select HAVE_RCU_TABLE_FREE if SMP select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_SYSCALL_TRACEPOINTS select HAVE_UID16 diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h index 0baf7f0..8cb5552 100644 --- a/arch/arm/include/asm/tlb.h +++ b/arch/arm/include/asm/tlb.h @@ -35,12 +35,39 @@ #define MMU_GATHER_BUNDLE 8 +#ifdef CONFIG_HAVE_RCU_TABLE_FREE +static inline void __tlb_remove_table(void *_table) +{ + free_page_and_swap_cache((struct page *)_table); +} + +struct mmu_table_batch { + struct rcu_head rcu; + unsigned int nr; + void *tables[0]; +}; + +#define MAX_TABLE_BATCH \ + ((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *)) + +extern void tlb_table_flush(struct mmu_gather *tlb); +extern void tlb_remove_table(struct mmu_gather *tlb, void *table); + +#define tlb_remove_entry(tlb,entry) tlb_remove_table(tlb,entry) +#else +#define tlb_remove_entry(tlb,entry) tlb_remove_page(tlb,entry) +#endif /* CONFIG_HAVE_RCU_TABLE_FREE */ + /* * TLB handling. This allows us to remove pages from the page * tables, and efficiently handle the TLB issues. */ struct mmu_gather { struct mm_struct *mm; +#ifdef CONFIG_HAVE_RCU_TABLE_FREE + struct mmu_table_batch *batch; + unsigned int need_flush; +#endif unsigned int fullmm; struct vm_area_struct *vma; unsigned long start, end; @@ -101,6 +128,9 @@ static inline void __tlb_alloc_page(struct mmu_gather *tlb) static inline void tlb_flush_mmu(struct mmu_gather *tlb) { tlb_flush(tlb); +#ifdef CONFIG_HAVE_RCU_TABLE_FREE + tlb_table_flush(tlb); +#endif free_pages_and_swap_cache(tlb->pages, tlb->nr); tlb->nr = 0; if (tlb->pages == tlb->local) @@ -119,6 +149,10 @@ tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start tlb->pages = tlb->local; tlb->nr = 0; __tlb_alloc_page(tlb); + +#ifdef CONFIG_HAVE_RCU_TABLE_FREE + tlb->batch = NULL; +#endif } static inline void @@ -195,7 +229,7 @@ static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte, tlb_add_flush(tlb, addr + SZ_1M); #endif - tlb_remove_page(tlb, pte); + tlb_remove_entry(tlb, pte); } static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp, @@ -203,7 +237,7 @@ static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp, { #ifdef CONFIG_ARM_LPAE tlb_add_flush(tlb, addr); - tlb_remove_page(tlb, virt_to_page(pmdp)); + tlb_remove_entry(tlb, virt_to_page(pmdp)); #endif }