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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0152C4332F for ; Fri, 6 May 2022 13:16:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1392316AbiEFNU1 (ORCPT ); Fri, 6 May 2022 09:20:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42408 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1392303AbiEFNUZ (ORCPT ); Fri, 6 May 2022 09:20:25 -0400 Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BAD3163BEA; Fri, 6 May 2022 06:16:41 -0700 (PDT) Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 246CvoBq027748; Fri, 6 May 2022 13:15:25 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : subject : from : to : cc : date : in-reply-to : references : content-type : mime-version : content-transfer-encoding; s=pp1; bh=xscNj3LKneLSbobsh3Ku1jl1vBQ8kIYhyMEEDDClgkk=; b=oBJQd8ZmQELQLadl/nTQ3LRaxIO/aB6J2HboQ8BtrRYXRlcTMjQ42tG86DF5+sRI/Us2 6yu8YnHriU0eFlcupkHKrl5OxO6l9qZQOtyx5XnV8n6fWIF5tm+4Xe6HLE0FVlZwA4u6 kFoAKCVEO22F/gM0owTO4fXUMywSG4eelo40bGXyRJwUwJP8fgeMEf2giutmEehQ3ILo VMW19KhYJUNwWTFL+36LFCX1mTzjraYcsur9KBqO1jctjg9DQeNWddzlAAqMquqYAopw YD8BUDGUByovfvkdobmUJ/1Kk4HpVfdE5WguUCW42hdJhdEFoqQmDOfvveZrLJzKpLro VQ== Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3fw451rbr6-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 06 May 2022 13:15:25 +0000 Received: from m0098419.ppops.net (m0098419.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 246DFOoT003453; Fri, 6 May 2022 13:15:24 GMT Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3fw451rbpu-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 06 May 2022 13:15:24 +0000 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 246D7fbj009330; Fri, 6 May 2022 13:15:21 GMT Received: from b06cxnps4074.portsmouth.uk.ibm.com (d06relay11.portsmouth.uk.ibm.com [9.149.109.196]) by ppma03ams.nl.ibm.com with ESMTP id 3ftp7fwh3v-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 06 May 2022 13:15:21 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 246DFIxB41288002 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 6 May 2022 13:15:18 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9686A4C04A; Fri, 6 May 2022 13:15:18 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C4FBB4C044; Fri, 6 May 2022 13:15:16 +0000 (GMT) Received: from sig-9-145-46-59.uk.ibm.com (unknown [9.145.46.59]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 6 May 2022 13:15:16 +0000 (GMT) Message-ID: <1424b9289049d0ad8b5c37a4e23ef70f0ef0f83d.camel@linux.ibm.com> Subject: Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary From: Niklas Schnelle To: Arnd Bergmann , "Maciej W. Rozycki" Cc: Bjorn Helgaas , Arnd Bergmann , Greg Kroah-Hartman , Linux Kernel Mailing List , linux-arch , linux-pci , Richard Henderson , Ivan Kokshaysky , Matt Turner , Russell King , Catalin Marinas , Will Deacon , Geert Uytterhoeven , Michal Simek , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Michael Ellerman , Paul Walmsley , Palmer Dabbelt , Albert Ou , Yoshinori Sato , Rich Felker , "David S. Miller" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "open list:ALPHA PORT" , "moderated list:ARM PORT" , "open list:IA64 (Itanium) PLATFORM" , "open list:M68K ARCHITECTURE" , "open list:MIPS" , "open list:PARISC ARCHITECTURE" , "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" , "open list:RISC-V ARCHITECTURE" , "open list:SUPERH" , "open list:SPARC + UltraSPARC (sparc/sparc64)" Date: Fri, 06 May 2022 15:15:16 +0200 In-Reply-To: References: <20220505161028.GA492600@bhelgaas> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-18.el8) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: -L36l-JGRIpdeUlE9r-XG_S8uzvQEAie X-Proofpoint-GUID: C-8WDwnxsOa89z3OSfQYEbBf2zCP5zSo X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.858,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-05-06_04,2022-05-06_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 spamscore=0 bulkscore=0 mlxscore=0 adultscore=0 phishscore=0 suspectscore=0 priorityscore=1501 clxscore=1015 mlxlogscore=852 malwarescore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2205060074 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Fri, 2022-05-06 at 14:53 +0200, Arnd Bergmann wrote: > On Fri, May 6, 2022 at 2:27 PM Maciej W. Rozycki wrote: > > On Fri, 6 May 2022, Arnd Bergmann wrote: > > > > > > If this is PCI/PCIe indeed, then an I/O access is just a different bit > > > > pattern put on the bus/in the TLP in the address phase. So what is there > > > > inherent to the s390 architecture that prevents that different bit pattern > > > > from being used? > > > > > > The hardware design for PCI on s390 is very different from any other > > > architecture, and more abstract. Rather than implementing MMIO register > > > access as pointer dereference, this is a separate CPU instruction that > > > takes a device/bar plus offset as arguments rather than a pointer, and > > > Linux encodes this back into a fake __iomem token. > > > > OK, that seems to me like a reasonable and quite a clean design (on the > > hardware side). > > > > So what happens if the instruction is given an I/O rather than memory BAR > > as the relevant argument? Is the address space indicator bit (bit #0) > > simply ignored or what? > > Not sure. My best guess is that it would actually work as you'd expect, > but is deliberately left out of the architecture specification so they don't > have to to validate the correctness. Note that only a small number of > PCIe cards are actually supported by IBM, and I think the firmware > only passes devices to the OS if they are whitelisted. > > Arnd Yes, though in Linux we do try hard to work with whatever is plugged in. We did benefit from this in the past working with a new NIC from a different vendor with 0 additional changes. Also you can use vfio-pci to pass-through arbitrary PCI devices to a QEMU emulating s390x.