From patchwork Mon Nov 2 12:17:11 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Juergen Gross X-Patchwork-Id: 317316 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 78240C4742C for ; Mon, 2 Nov 2020 12:17:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0DFB122277 for ; Mon, 2 Nov 2020 12:17:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="c7mQbtZn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728484AbgKBMRZ (ORCPT ); Mon, 2 Nov 2020 07:17:25 -0500 Received: from mx2.suse.de ([195.135.220.15]:48072 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728663AbgKBMRY (ORCPT ); Mon, 2 Nov 2020 07:17:24 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1604319443; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=D5JMDRpr4XQxvKEMDlxF9Pb3B5vWxz5wnOaFOseKtlY=; b=c7mQbtZnlaE34iNFJUpbBED3hsvGdXJd+n7dYEuAGX1JQBL6veXXVKJsUOt+3Q/CzL9hGM o6rCWo1qA6JoSha3NqW7CpoIGo1XTv/VhWIc6Br4JRo737Jzeb4bePBXYz0FfNyiGS+V1f 0fCRx1ZCFfUcKLOYrzzdcPRWpABr3jk= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id A3B14AF3D for ; Mon, 2 Nov 2020 12:17:23 +0000 (UTC) From: Juergen Gross To: stable@vger.kernel.org Subject: [PATCH 03/14] xen/events: add a proper barrier to 2-level uevent unmasking Date: Mon, 2 Nov 2020 13:17:11 +0100 Message-Id: <20201102121722.10940-4-jgross@suse.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201102121722.10940-1-jgross@suse.com> References: <20201102121722.10940-1-jgross@suse.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org A follow-up patch will require certain write to happen before an event channel is unmasked. While the memory barrier is not strictly necessary for all the callers, the main one will need it. In order to avoid an extra memory barrier when using fifo event channels, mandate evtchn_unmask() to provide write ordering. The 2-level event handling unmask operation is missing an appropriate barrier, so add it. Fifo event channels are fine in this regard due to using sync_cmpxchg(). This is part of XSA-332. This is upstream commit 4d3fe31bd993ef504350989786858aefdb877daa Cc: stable@vger.kernel.org Suggested-by: Julien Grall Signed-off-by: Juergen Gross Reviewed-by: Julien Grall Reviewed-by: Wei Liu --- drivers/xen/events/events_2l.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/xen/events/events_2l.c b/drivers/xen/events/events_2l.c index 8edef51c92e5..e4b75693600e 100644 --- a/drivers/xen/events/events_2l.c +++ b/drivers/xen/events/events_2l.c @@ -91,6 +91,8 @@ static void evtchn_2l_unmask(unsigned port) BUG_ON(!irqs_disabled()); + smp_wmb(); /* All writes before unmask must be visible. */ + if (unlikely((cpu != cpu_from_evtchn(port)))) do_hypercall = 1; else {