From patchwork Tue Nov 3 14:29:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Juergen Gross X-Patchwork-Id: 317266 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 EF872C6369E for ; Tue, 3 Nov 2020 14:30:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A18CA223C7 for ; Tue, 3 Nov 2020 14:30:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="JDrx06WU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729580AbgKCOae (ORCPT ); Tue, 3 Nov 2020 09:30:34 -0500 Received: from mx2.suse.de ([195.135.220.15]:38794 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729699AbgKCO3N (ORCPT ); Tue, 3 Nov 2020 09:29:13 -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=1604413752; 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=JDrx06WUZSsCKYPicjdunJ8jDCJrYN33C7EcSuL+tSkgrtk0MBIHIjnd8IvgJbBl3wktpo 0QIpf1z0SFMPCI1f7D5MlVVt0bEvgxlik4YLdrTCi4N784gu0wFvzRU0BlN3Ul7Xk6G1o7 aK7IugROLC++Jg6ACWPtO44QT+iIPUw= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2922CB29C for ; Tue, 3 Nov 2020 14:29:12 +0000 (UTC) From: Juergen Gross To: stable@vger.kernel.org Subject: [PATCH v2 03/14] xen/events: add a proper barrier to 2-level uevent unmasking Date: Tue, 3 Nov 2020 15:29:00 +0100 Message-Id: <20201103142911.21980-4-jgross@suse.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201103142911.21980-1-jgross@suse.com> References: <20201103142911.21980-1-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 {