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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 B9861CA9EB5 for ; Mon, 4 Nov 2019 14:35:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9574121D7D for ; Mon, 4 Nov 2019 14:35:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728938AbfKDOfG (ORCPT ); Mon, 4 Nov 2019 09:35:06 -0500 Received: from mx2.suse.de ([195.135.220.15]:51992 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728416AbfKDOfG (ORCPT ); Mon, 4 Nov 2019 09:35:06 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 8DE98AD17; Mon, 4 Nov 2019 14:35:04 +0000 (UTC) Subject: Re: [Xen-devel] [PATCH] xen/events: remove event handling recursion detection To: Juergen Gross Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, Stefano Stabellini , Boris Ostrovsky References: <20191104135812.2314-1-jgross@suse.com> From: Jan Beulich Message-ID: <40cba9d9-24b0-3141-4ba8-02e03049f1bf@suse.com> Date: Mon, 4 Nov 2019 15:35:09 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20191104135812.2314-1-jgross@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04.11.2019 14:58, Juergen Gross wrote: > __xen_evtchn_do_upcall() contains guards against being called > recursively. This mechanism was introduced in the early pvops times > (kernel 2.6.26) when there were still Xen versions around not honoring > disabled interrupts for sending events to pv guests. > > This was changed in Xen 3.0, which is much older than any Xen version > supported by the kernel, so the recursion detection can be removed. Would you mind pointing out which exact change(s) this was(were)? It had always been my understanding that the recursion detection was mainly to guard against drivers re-enabling interrupts transiently in their handlers (which in turn may no longer be an issue in modern Linux kernels). Jan