From patchwork Tue Nov 17 13:05:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 325432 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=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 7EFAFC64E75 for ; Tue, 17 Nov 2020 13:12:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 21867246BB for ; Tue, 17 Nov 2020 13:12:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="wLv3rHsI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729781AbgKQNMF (ORCPT ); Tue, 17 Nov 2020 08:12:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:41964 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729723AbgKQNMD (ORCPT ); Tue, 17 Nov 2020 08:12:03 -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 B2B0B24199; Tue, 17 Nov 2020 13:12:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605618723; bh=cBaCki1wSPt+czcXSB+QD0oaExPggu2lSlynJL3wzKc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wLv3rHsINJMsIpPhgjDI5Qb4pboOzZkqbJHk028oCTpc7IO6E1XA4msaGyjcivhqR ghPadRSGGgzi8QV8+yI8bFkhBXYDowXGfiKptAUS1w8fZd0FFZsaapB8wviL0boPzu vAmu0cvip4cFwkWEyZ5PTuVjBRG7EHYEZ8FiXwqc= 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 4.9 63/78] xen/events: add a proper barrier to 2-level uevent unmasking Date: Tue, 17 Nov 2020 14:05:29 +0100 Message-Id: <20201117122112.195319817@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201117122109.116890262@linuxfoundation.org> References: <20201117122109.116890262@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 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 @@ -90,6 +90,8 @@ 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 {