From patchwork Tue Jun 30 17:37:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 11634467 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7B14A6C1 for ; Tue, 30 Jun 2020 17:42:51 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5472F20775 for ; Tue, 30 Jun 2020 17:42:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="o181x/iq"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="0q+Ziga1" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5472F20775 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-Id:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=a6lsNkgevgajSDwIE1LxTxrgMckPs6MoCgwiO2zH7gA=; b=o181x/iqYD8mUgWlVN4JT1c+d EqY6lH/fyWptFJ6AiVAg9eohUKX7J9SJyF6YanV6v6tjtTVQgwwbvI/DF2I31uOBEy8lyBh6LwGJ1 KjMHb2XoEWQxuxl+6f+T8QJdKyiVNpFlerjg2kvvIUvqeKopzCcC956U70HjC4ziVPnMXOi7BPUPG 3oAQp9EO2j5gbWiwM4FYOt5XeoOKCV4SzklqPpZLtVKq/LiqRjUjEZpGehMVhShArgb8j4vqzlmSt BUtofq20z2bLvD5WTTElTw9+FyFVg+L6o6wVcma4iXT0ztwW2qTKKtVCSbYotYKzvajRGV31C6tRI CbNHrBvxg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jqKFc-0002du-SL; Tue, 30 Jun 2020 17:40:59 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jqKDg-0001Wl-Br for linux-arm-kernel@lists.infradead.org; Tue, 30 Jun 2020 17:39:01 +0000 Received: from localhost.localdomain (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 218CE208D5; Tue, 30 Jun 2020 17:38:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593538734; bh=9ta772X0LhIYPaLbgcx1JUvYo6hXV5XVnuUlAptrUOU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0q+Ziga1tPlskSYQCOixoO6Z7LOXNz3B6jLLCGqxp/nOY1c+yQMi4dmX9JM37+9y0 ZK9XtOGvfQUWp0T7YRsp5zuJSE8D4Xcg5v8WcxEy/7r+jxhV6fRVjnfN6L3KkrZKkU ebDLdVemnERh2RnFrQjwFEjyJUmdx4Rab8Jh0TpI= From: Will Deacon To: linux-kernel@vger.kernel.org Subject: [PATCH 17/18] arm64: alternatives: Remove READ_ONCE() usage during patch operation Date: Tue, 30 Jun 2020 18:37:33 +0100 Message-Id: <20200630173734.14057-18-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200630173734.14057-1-will@kernel.org> References: <20200630173734.14057-1-will@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200630_133856_912772_F71E15DA X-CRM114-Status: GOOD ( 13.54 ) X-Spam-Score: -5.2 (-----) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-5.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at https://www.dnswl.org/, high trust [198.145.29.99 listed in list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.0 DKIMWL_WL_HIGH DKIMwl.org - Whitelisted High sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , "Michael S. Tsirkin" , Peter Zijlstra , Catalin Marinas , Jason Wang , virtualization@lists.linux-foundation.org, Will Deacon , Arnd Bergmann , Alan Stern , Sami Tolvanen , Matt Turner , kernel-team@android.com, Marco Elver , Kees Cook , "Paul E. McKenney" , Boqun Feng , Josh Triplett , Ivan Kokshaysky , linux-arm-kernel@lists.infradead.org, Richard Henderson , Nick Desaulniers , linux-alpha@vger.kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org In preparation for patching the internals of READ_ONCE() itself, replace its usage on the alternatives patching patch with a volatile variable instead. Signed-off-by: Will Deacon --- arch/arm64/kernel/alternative.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c index d1757ef1b1e7..87bca8d44084 100644 --- a/arch/arm64/kernel/alternative.c +++ b/arch/arm64/kernel/alternative.c @@ -21,7 +21,8 @@ #define ALT_ORIG_PTR(a) __ALT_PTR(a, orig_offset) #define ALT_REPL_PTR(a) __ALT_PTR(a, alt_offset) -static int all_alternatives_applied; +/* Volatile, as we may be patching the guts of READ_ONCE() */ +static volatile int all_alternatives_applied; static DECLARE_BITMAP(applied_alternatives, ARM64_NCAPS); @@ -217,7 +218,7 @@ static int __apply_alternatives_multi_stop(void *unused) /* We always have a CPU 0 at this point (__init) */ if (smp_processor_id()) { - while (!READ_ONCE(all_alternatives_applied)) + while (!all_alternatives_applied) cpu_relax(); isb(); } else { @@ -229,7 +230,7 @@ static int __apply_alternatives_multi_stop(void *unused) BUG_ON(all_alternatives_applied); __apply_alternatives(®ion, false, remaining_capabilities); /* Barriers provided by the cache flushing */ - WRITE_ONCE(all_alternatives_applied, 1); + all_alternatives_applied = 1; } return 0;