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=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 1B621C388F7 for ; Tue, 3 Nov 2020 21:02:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DEF4D22226 for ; Tue, 3 Nov 2020 21:02:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604437355; bh=nOGdb9uR5h52LS2DyYbrmfF9dn0bqiJYyKU3d5omfJA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=YuS3x+hBVhv32PM9QUjvz1PvFVwjIo1zG1mfg3oHtqluzSsgNG8E5/evvI/itWdXu uyNXfhQooc/PTpJ9Qy6xK5C+uX/mPjFJvYdmV0+v0wYr2fMdekUoUhkr3lLDsp0Vyo ELyrJ+HIvpjUk/cw5eiwOd5skDamOXXXivbNMDcY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387663AbgKCVCf (ORCPT ); Tue, 3 Nov 2020 16:02:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:39618 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732167AbgKCVCd (ORCPT ); Tue, 3 Nov 2020 16:02:33 -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 034C620757; Tue, 3 Nov 2020 21:02:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604437351; bh=nOGdb9uR5h52LS2DyYbrmfF9dn0bqiJYyKU3d5omfJA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ftB9kqINNEFuSz6HzPoH4MB9OsOmUl2mOqKVirs5KBBNyukzYDFszwS3yuXroxw6w gee6WOP5pdIjctqHcVswvzXIVtRw2yeId+NRFD1gpGxk+SP/hPsSwqOqK3ptuGzTQB aPWeyEKrbsdwFL8rJgfzF0G1snTggPc0Ps6Ydb6k= 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 4.19 038/191] xen/events: add a proper barrier to 2-level uevent unmasking Date: Tue, 3 Nov 2020 21:35:30 +0100 Message-Id: <20201103203237.653154050@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201103203232.656475008@linuxfoundation.org> References: <20201103203232.656475008@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 {