From patchwork Tue Nov 3 14:13:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Juergen Gross X-Patchwork-Id: 317282 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, URIBL_BLOCKED, 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 7C752C6369E for ; Tue, 3 Nov 2020 14:15:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2705722243 for ; Tue, 3 Nov 2020 14:15:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="Vnd+NQtk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729641AbgKCOPJ (ORCPT ); Tue, 3 Nov 2020 09:15:09 -0500 Received: from mx2.suse.de ([195.135.220.15]:56018 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729649AbgKCONW (ORCPT ); Tue, 3 Nov 2020 09:13:22 -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=1604412801; 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=Vnd+NQtksUdmw6sSkNklQ+rDCEhOxx+HmFquW9chXor25wzsIZvsUT/q9TCGlR6S8ip2MZ KMS1eGAS9FMTl49AUnJ1brbl3OgNYZgN2CkqkdLAczM1w1M188DRdsn6qARSWy/5yqUWNU Rk2HkJmgzjGvzFfMuBmOuThiRRxwhOU= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id B297BB298 for ; Tue, 3 Nov 2020 14:13:21 +0000 (UTC) From: Juergen Gross To: stable@vger.kernel.org Subject: [PATCH v2 02/13] xen/events: add a proper barrier to 2-level uevent unmasking Date: Tue, 3 Nov 2020 15:13:10 +0100 Message-Id: <20201103141321.20346-3-jgross@suse.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201103141321.20346-1-jgross@suse.com> References: <20201103141321.20346-1-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 {