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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 45248C2BA83 for ; Wed, 12 Feb 2020 13:07:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 05ACA2073C for ; Wed, 12 Feb 2020 13:07:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="iJw80NxS" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 05ACA2073C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8FC8E6B044C; Wed, 12 Feb 2020 08:07:43 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8AC576B044D; Wed, 12 Feb 2020 08:07:43 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 79BBA6B044E; Wed, 12 Feb 2020 08:07:43 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0075.hostedemail.com [216.40.44.75]) by kanga.kvack.org (Postfix) with ESMTP id 61B906B044C for ; Wed, 12 Feb 2020 08:07:43 -0500 (EST) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id EB3584DB4 for ; Wed, 12 Feb 2020 13:07:42 +0000 (UTC) X-FDA: 76481501964.25.party07_7d8880b951938 X-HE-Tag: party07_7d8880b951938 X-Filterd-Recvd-Size: 3307 Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) by imf45.hostedemail.com (Postfix) with ESMTP for ; Wed, 12 Feb 2020 13:07:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581512862; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=dFhflF1hBhJOha4DSYN37Djg7mP7A+q3ubsJivvLvf0=; b=iJw80NxSpT3zCZH3WlbhVue/D5Nd+0wx7lbQwKWnY1bAtnlT+dr1Lep9JAYv9VvbVbDImR d6zgftNHx0DKkEaEX3NoWQEg0oEdWtoqpr9zca+YfsoOesaRoo/AHKMkNt08PgvE5y8eKs wXtlHx5rpQ34xuEdZxDy4EZXOgbY8Js= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-426-1_op5JqGMYGTxKIvthVypQ-1; Wed, 12 Feb 2020 08:07:38 -0500 X-MC-Unique: 1_op5JqGMYGTxKIvthVypQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6475713E4; Wed, 12 Feb 2020 13:07:36 +0000 (UTC) Received: from gondolin (dhcp-192-195.str.redhat.com [10.33.192.195]) by smtp.corp.redhat.com (Postfix) with ESMTP id A81F219C69; Wed, 12 Feb 2020 13:07:31 +0000 (UTC) Date: Wed, 12 Feb 2020 14:07:29 +0100 From: Cornelia Huck To: Christian Borntraeger Cc: david@redhat.com, Ulrich.Weigand@de.ibm.com, aarcange@redhat.com, akpm@linux-foundation.org, frankja@linux.vnet.ibm.com, gor@linux.ibm.com, imbrenda@linux.ibm.com, kvm@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, mimu@linux.ibm.com, thuth@redhat.com Subject: Re: [PATCH v2 RFC] KVM: s390/interrupt: do not pin adapter interrupt pages Message-ID: <20200212140729.21209127.cohuck@redhat.com> In-Reply-To: References: <567B980B-BDA5-4EF3-A96E-1542D11F2BD4@redhat.com> <20200211092341.3965-1-borntraeger@de.ibm.com> <20200212133908.6c6c9072.cohuck@redhat.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 12 Feb 2020 13:44:53 +0100 Christian Borntraeger wrote: > On 12.02.20 13:39, Cornelia Huck wrote: > [...] > > >> + */ > >> + return 0; > > > > Given that this function now always returns 0, we basically get a > > completely useless roundtrip into the kernel when userspace is trying > > to setup the mappings. > > > > Can we define a new IO_ADAPTER_MAPPING_NOT_NEEDED or so capability that > > userspace can check? > > Nack. This is one system call per initial indicator ccw. This is so seldom > and cheap that I do not see a point in optimizing this. NB that zpci also calls this. Probably a rare event there as well. > > > > This change in behaviour probably wants a change in the documentation > > as well. > > Yep.