From patchwork Tue Nov 3 08:41:40 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Juergen Gross X-Patchwork-Id: 317294 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 17E3FC388F2 for ; Tue, 3 Nov 2020 08:41:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B39B8223BF for ; Tue, 3 Nov 2020 08:41:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="inlHG1mA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725968AbgKCIlw (ORCPT ); Tue, 3 Nov 2020 03:41:52 -0500 Received: from mx2.suse.de ([195.135.220.15]:51062 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726211AbgKCIlw (ORCPT ); Tue, 3 Nov 2020 03:41:52 -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=1604392911; 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=ArdBxJEtoWfKZs8sJ+QIy7SyLsALyipHGMbBlsjYcxs=; b=inlHG1mAu7TM9Kwbxq82Kmv4+A99AypG89t6PkmkFXm4Mvk1SvCM8wLTxJfm4N96EjFpYh asRmFBstvSoQn59+sS/TtVio+ST+yqG/ZkO8YObxm1IZeqd8JsmmPqvr96HHo1411EkNTd 3N/Cyin31MnkYYL1oi6hkB9jALiLv08= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id F07FBB05D for ; Tue, 3 Nov 2020 08:41:50 +0000 (UTC) From: Juergen Gross To: stable@vger.kernel.org Subject: [PATCH 03/13] xen/events: add a proper barrier to 2-level uevent unmasking Date: Tue, 3 Nov 2020 09:41:40 +0100 Message-Id: <20201103084150.8625-4-jgross@suse.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201103084150.8625-1-jgross@suse.com> References: <20201103084150.8625-1-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 bdff01095f54..5c622c5ad490 100644 --- a/drivers/xen/events/events_2l.c +++ b/drivers/xen/events/events_2l.c @@ -90,6 +90,8 @@ 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 {