From patchwork Tue Mar 22 10:11:28 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 64154 Delivered-To: patch@linaro.org Received: by 10.112.199.169 with SMTP id jl9csp1959233lbc; Tue, 22 Mar 2016 03:13:06 -0700 (PDT) X-Received: by 10.98.42.150 with SMTP id q144mr52756592pfq.73.1458641586422; Tue, 22 Mar 2016 03:13:06 -0700 (PDT) Return-Path: Received: from bombadil.infradead.org (bombadil.infradead.org. [2001:1868:205::9]) by mx.google.com with ESMTPS id q76si9566122pfa.60.2016.03.22.03.13.06 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 22 Mar 2016 03:13:06 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org designates 2001:1868:205::9 as permitted sender) client-ip=2001:1868:205::9; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org designates 2001:1868:205::9 as permitted sender) smtp.mailfrom=linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1aiJIK-0003pb-Ui; Tue, 22 Mar 2016 10:12:12 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1aiJIH-0003mB-Gv for linux-arm-kernel@lists.infradead.org; Tue, 22 Mar 2016 10:12:09 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D0C9B3A1; Tue, 22 Mar 2016 03:10:42 -0700 (PDT) Received: from leverpostej.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 20FDA3F25F; Tue, 22 Mar 2016 03:11:45 -0700 (PDT) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Subject: [PATCH] arm64: mm: allow preemption in copy_to_user_page Date: Tue, 22 Mar 2016 10:11:28 +0000 Message-Id: <1458641488-21455-1-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160322_031209_573926_12EABF4A X-CRM114-Status: GOOD ( 10.04 ) X-Spam-Score: -6.9 (------) X-Spam-Report: SpamAssassin version 3.4.0 on bombadil.infradead.org summary: Content analysis details: (-6.9 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at http://www.dnswl.org/, high trust [217.140.101.70 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -0.0 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Catalin Marinas , Will Deacon MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org Currently we disable preemption in copy_to_user_page; a behaviour that we inherited from the 32-bit arm code. This was necessary for older cores without broadcast data cache maintenance, and ensured that cache lines were dirtied and cleaned by the same CPU. On these systems dirty cache line migration was not possible, so this was sufficient to guarantee coherency. On contemporary systems, cache coherence protocols permit (dirty) cache lines to migrate between CPUs as a result of speculation, prefetching, and other behaviours. To account for this, in ARMv8 data cache maintenance operations are broadcast and affect all data caches in the domain associated with the VA (i.e. ISH for kernel and user mappings). In __switch_to we ensure that tasks can be safely migrated in the middle of a maintenance sequence, using a dsb(ish) to ensure prior explicit memory accesses are observed and cache maintenance operations are completed before a task can be run on another CPU. Given the above, it is not necessary to disable preemption in copy_to_user_page. This patch removes the preempt_{disable,enable} calls, permitting preemption. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Will Deacon --- arch/arm64/mm/flush.c | 4 ---- 1 file changed, 4 deletions(-) -- 1.9.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c index 60585bd..dbd12ea 100644 --- a/arch/arm64/mm/flush.c +++ b/arch/arm64/mm/flush.c @@ -58,17 +58,13 @@ static void flush_ptrace_access(struct vm_area_struct *vma, struct page *page, * Copy user data from/to a page which is mapped into a different processes * address space. Really, we want to allow our "user space" model to handle * this. - * - * Note that this code needs to run on the current CPU. */ void copy_to_user_page(struct vm_area_struct *vma, struct page *page, unsigned long uaddr, void *dst, const void *src, unsigned long len) { - preempt_disable(); memcpy(dst, src, len); flush_ptrace_access(vma, page, uaddr, dst, len); - preempt_enable(); } void __sync_icache_dcache(pte_t pte, unsigned long addr)