From mboxrd@z Thu Jan 1 00:00:00 1970 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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 A4AB8C63697 for ; Tue, 17 Nov 2020 14:00:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 42E2120829 for ; Tue, 17 Nov 2020 14:00:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="O8Ho6Lik" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729542AbgKQNRG (ORCPT ); Tue, 17 Nov 2020 08:17:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:49248 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729704AbgKQNRF (ORCPT ); Tue, 17 Nov 2020 08:17:05 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 48DAD2225B; Tue, 17 Nov 2020 13:17:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605619024; bh=aCmNFqxGqjg0MaIKn3bMohrVDuuo7zL289AJAp+FoPo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=O8Ho6LikQejU8kz85n8uZaMyOzajJY0wX32yrO6iKOR6Rof7iHbo2HnquHl7AtbcV i1XFIEVXZuzQ8May8K8Yd6wdbR0c5zkzzzDGu/7graF7M5FjJZN+PP5ZMIZBDPomJX 9qjkbVVw9MHJE3zla/Ku2LEEt1o3bs6sD1vsTsV0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , Julien Grall , Juergen Gross , Julien Grall , Wei Liu Subject: [PATCH 4.14 70/85] xen/events: add a proper barrier to 2-level uevent unmasking Date: Tue, 17 Nov 2020 14:05:39 +0100 Message-Id: <20201117122114.467288437@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201117122111.018425544@linuxfoundation.org> References: <20201117122111.018425544@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Juergen Gross commit 4d3fe31bd993ef504350989786858aefdb877daa upstream. 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. Cc: stable@vger.kernel.org Suggested-by: Julien Grall Signed-off-by: Juergen Gross Reviewed-by: Julien Grall Reviewed-by: Wei Liu Signed-off-by: Greg Kroah-Hartman --- drivers/xen/events/events_2l.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/xen/events/events_2l.c +++ b/drivers/xen/events/events_2l.c @@ -91,6 +91,8 @@ static void evtchn_2l_unmask(unsigned po BUG_ON(!irqs_disabled()); + smp_wmb(); /* All writes before unmask must be visible. */ + if (unlikely((cpu != cpu_from_evtchn(port)))) do_hypercall = 1; else {