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 F32CBC388F7 for ; Tue, 3 Nov 2020 22:10:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C0EC821556 for ; Tue, 3 Nov 2020 22:10:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604441421; bh=aJlYSdk1Jt8bY3ZioFvqUerhdlA1snR2dbKgWVoz78M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=C9cRq8FZD0n2gmsfWkBxwmPq4tRRhqD8lO7P1qla201OajN5dY973+pQOA+Di6zTX s087BTbgRxsoub7yi6pLjJR9duRSrq8ccm5bySGrn1de94iDz6Si6IYEQT6VyssFx4 b3I+kGo6wOsRnTaHRduMWfzC2zw9N1rBGjyKh0H0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731766AbgKCWKU (ORCPT ); Tue, 3 Nov 2020 17:10:20 -0500 Received: from mail.kernel.org ([198.145.29.99]:47410 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729799AbgKCUho (ORCPT ); Tue, 3 Nov 2020 15:37:44 -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 37AB8223AB; Tue, 3 Nov 2020 20:37:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604435862; bh=aJlYSdk1Jt8bY3ZioFvqUerhdlA1snR2dbKgWVoz78M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lzEU/fBynSzYEnzCNRTdVoiQ1A5b45ek09baeBXE3hh9CtAzBuUKg0qzKbNAHjGWo ZFeaKc6pJ80Q/mG4Zt7CGddjhTKvXnT2UDPYmql16BceN4MEm3ektyJOa61Dh+0lrm +CrOLHvO1dWve/0Lph/ST+1h238k6ycmXZZlwiM0= 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 5.9 002/391] xen/events: add a proper barrier to 2-level uevent unmasking Date: Tue, 3 Nov 2020 21:30:53 +0100 Message-Id: <20201103203348.310892907@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201103203348.153465465@linuxfoundation.org> References: <20201103203348.153465465@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(evtchn_port BUG_ON(!irqs_disabled()); + smp_wmb(); /* All writes before unmask must be visible. */ + if (unlikely((cpu != cpu_from_evtchn(port)))) do_hypercall = 1; else {