From patchwork Tue Nov 17 13:05:12 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 328017 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 6E9FBC64E7D for ; Tue, 17 Nov 2020 14:06:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B0DFE221FC for ; Tue, 17 Nov 2020 14:06:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="GMkPwYYL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729224AbgKQNIM (ORCPT ); Tue, 17 Nov 2020 08:08:12 -0500 Received: from mail.kernel.org ([198.145.29.99]:36642 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729236AbgKQNIJ (ORCPT ); Tue, 17 Nov 2020 08:08:09 -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 330BA2225B; Tue, 17 Nov 2020 13:08:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605618487; bh=cBaCki1wSPt+czcXSB+QD0oaExPggu2lSlynJL3wzKc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GMkPwYYLSZtIvHMNMNsj1Xo7NxYrRkH3cf8N8yUZSpp+6LlvcXQlr9gqX1om+yP44 XDJePKLBoT0sgaKrZ2NwnMvIxd+6NJy9m7Sqv5aNtwfsmX0lBcu84utGD3lsP9UlVi Rcz9Otz7b7P30wd2r0BVEZgKyKsOB6ONqobOsunw= 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 4.4 49/64] xen/events: add a proper barrier to 2-level uevent unmasking Date: Tue, 17 Nov 2020 14:05:12 +0100 Message-Id: <20201117122108.587012647@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201117122106.144800239@linuxfoundation.org> References: <20201117122106.144800239@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 {