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 257A1C2D0A3 for ; Tue, 3 Nov 2020 20:53:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA1AE223C6 for ; Tue, 3 Nov 2020 20:53:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604436813; bh=nOGdb9uR5h52LS2DyYbrmfF9dn0bqiJYyKU3d5omfJA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=rlmokpLs/Z77QWT/oZapE7YtBIEr8nWU5jVAaoudvDrod23sn/1AUYIKcqbbM1Md0 f2DkPVGl5IKD6oAM7xieJId7oHYs0R0bImv2H13MYxuFCMSJp4cV+GKyKjfikGP3IL RqQN3BaiyJMi4Q7gQHXayiMOR52qYSREzSymk54M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732364AbgKCUxc (ORCPT ); Tue, 3 Nov 2020 15:53:32 -0500 Received: from mail.kernel.org ([198.145.29.99]:51398 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731746AbgKCUx1 (ORCPT ); Tue, 3 Nov 2020 15:53:27 -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 6CDF822226; Tue, 3 Nov 2020 20:53:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604436806; bh=nOGdb9uR5h52LS2DyYbrmfF9dn0bqiJYyKU3d5omfJA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lkFf+piJMCIdRuC/H6TxoodR/StPlwQIZf2/G1yRrnp1uIOjPsgzoLEvc3aP6agl2 9fGVvh4QL34XFTWC3UW/h2t0PpMqvKMjiZz1WmNh5v/LKzG1sH28mS1LiPY7AT88Ks psBzcynpEOWnANGYHkuBt0uiSNzAbK+seUDs/SEc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Julien Grall , Juergen Gross , Julien Grall , Wei Liu Subject: [PATCH 5.4 002/214] xen/events: add a proper barrier to 2-level uevent unmasking Date: Tue, 3 Nov 2020 21:34:10 +0100 Message-Id: <20201103203249.724325980@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201103203249.448706377@linuxfoundation.org> References: <20201103203249.448706377@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: linux-kernel@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 {