From mboxrd@z Thu Jan 1 00:00:00 1970 From: Niklas Schnelle Subject: Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary Date: Thu, 05 May 2022 10:10:15 +0200 Message-ID: References: <20220429135108.2781579-2-schnelle@linux.ibm.com> <20220504210840.GA469916@bhelgaas> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: 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 : content-transfer-encoding : mime-version; s=pp1; bh=z4sq9VpdyC1twtJvv6LraDF4oC5l7K1Gjqz/EX96h48=; b=byg8yPH7lB6IZpHqaGAW/IeqHBFw1qVNnemAYMuW6RqtAD2Pr44LXtY5qhdvLHHtmyHS zx9iz65kowFV3EWLgEN1WG/d59kZe4yfXhGahlw0zEySpnmOMpKtnTu1H+qcza8lcgus VP1jt7FqQK3My93W8lTLtP5pcjNasJUlrXI0Oj9oLP5ti+9vQ6TEUWY2ibcsPnUs14uv NmvMjJPL0KUnhOk2z1eHsYp83y9pSRyRUfpRV7sovwq8yCY9xzBZFlBb50MQwBEdnaiO 0N3pnELj4DvaEamDhYosnYTLvIbL2KA1mWAd5tpRBkVo6hFlV6xAvxmWORtU26wlKUnZ hw== In-Reply-To: List-ID: Content-Type: text/plain; charset="windows-1252" To: Arnd Bergmann , Bjorn Helgaas Cc: 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 , A On Wed, 2022-05-04 at 23:31 +0200, Arnd Bergmann wrote: > On Wed, May 4, 2022 at 11:08 PM Bjorn Helgaas wrote: > > On Fri, Apr 29, 2022 at 03:49:59PM +0200, Niklas Schnelle wrote: > > > We introduce a new HAS_IOPORT Kconfig option to indicate support for > > > I/O Port access. In a future patch HAS_IOPORT=3Dn will disable compil= ation > > > of the I/O accessor functions inb()/outb() and friends on architectur= es > > > which can not meaningfully support legacy I/O spaces such as s390 or > > > where such support is optional. > >=20 > > So you plan to drop inb()/outb() on architectures where I/O port space > > is optional? So even platforms that have I/O port space may not be > > able to use it? > >=20 > > This feels like a lot of work where the main benefit is to keep > > Kconfig from offering drivers that aren't of interest on s390. > >=20 > > Granted, there may be issues where inb()/outb() does the wrong thing > > such as dereferencing null pointers when I/O port space isn't > > implemented. I think that's a defect in inb()/outb() and could be > > fixed there. >=20 > The current implementation in asm-generic/io.h implements inb()/outb() > using readb()/writeb() with a fixed architecture specific offset. >=20 > There are three possible things that can happen here: >=20 > a) there is a host bridge driver that maps its I/O ports to this window, > and everything works > b) the address range is reserved and accessible but no host bridge > driver has mapped its registers there, so an access causes a > page fault > c) the architecture does not define an offset, and accessing low I/O > ports ends up as a NULL pointer dereference >=20 > The main goal is to avoid c), which is what happens on s390, but > can also happen elsewhere. Catching b) would be nice as well, > but is much harder to do from generic code as you'd need an > architecture specific inline asm statement to insert a ex_table > fixup, or a runtime conditional on each access. >=20 > Arnd Yes and to add to this, we did try a local solution in inb()/outb() before. This added a warning when they are used and we know at compile time that we're dealing with case c). This approach was nacked by Linus though as we were turning a compile time known broken case into a runtime one: https://lore.kernel.org/lkml/CAHk-=3Dwg80je=3DK7madF4e7WrRNp37e3qh6y10Svhdc= 7O8SZ_-8g@mail.gmail.com/ I do agree with this assesment and think this is the right=E2=84=A2 approach but it is more churn as can be seen by the size of this series. I think longer term it could be valuable though especially if more platforms phase out I/O port support like POWER9 for which this also allows filtering what drivers will never work. 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 4D30FC433F5 for ; Thu, 5 May 2022 08:12:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346517AbiEEIQW (ORCPT ); Thu, 5 May 2022 04:16:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48120 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234291AbiEEIQU (ORCPT ); Thu, 5 May 2022 04:16:20 -0400 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E487724080; Thu, 5 May 2022 01:12:41 -0700 (PDT) Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 2454o237019760; Thu, 5 May 2022 08:10:24 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 : content-transfer-encoding : mime-version; s=pp1; bh=z4sq9VpdyC1twtJvv6LraDF4oC5l7K1Gjqz/EX96h48=; b=byg8yPH7lB6IZpHqaGAW/IeqHBFw1qVNnemAYMuW6RqtAD2Pr44LXtY5qhdvLHHtmyHS zx9iz65kowFV3EWLgEN1WG/d59kZe4yfXhGahlw0zEySpnmOMpKtnTu1H+qcza8lcgus VP1jt7FqQK3My93W8lTLtP5pcjNasJUlrXI0Oj9oLP5ti+9vQ6TEUWY2ibcsPnUs14uv NmvMjJPL0KUnhOk2z1eHsYp83y9pSRyRUfpRV7sovwq8yCY9xzBZFlBb50MQwBEdnaiO 0N3pnELj4DvaEamDhYosnYTLvIbL2KA1mWAd5tpRBkVo6hFlV6xAvxmWORtU26wlKUnZ hw== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3fv7w5ayn0-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 05 May 2022 08:10:24 +0000 Received: from m0098394.ppops.net (m0098394.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 24580f9U005340; Thu, 5 May 2022 08:10:23 GMT Received: from ppma06fra.de.ibm.com (48.49.7a9f.ip4.static.sl-reverse.com [159.122.73.72]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3fv7w5ayks-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 05 May 2022 08:10:22 +0000 Received: from pps.filterd (ppma06fra.de.ibm.com [127.0.0.1]) by ppma06fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 245884X7030065; Thu, 5 May 2022 08:10:20 GMT Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by ppma06fra.de.ibm.com with ESMTP id 3fttcj2t2u-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 05 May 2022 08:10:19 +0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 2458AH1F53543266 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 5 May 2022 08:10:17 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4C65511C050; Thu, 5 May 2022 08:10:17 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7B05911C04A; Thu, 5 May 2022 08:10:15 +0000 (GMT) Received: from sig-9-145-85-251.uk.ibm.com (unknown [9.145.85.251]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 5 May 2022 08:10:15 +0000 (GMT) Message-ID: Subject: Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary From: Niklas Schnelle To: Arnd Bergmann , Bjorn Helgaas Cc: 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: Thu, 05 May 2022 10:10:15 +0200 In-Reply-To: References: <20220429135108.2781579-2-schnelle@linux.ibm.com> <20220504210840.GA469916@bhelgaas> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-18.el8) X-TM-AS-GCONF: 00 X-Proofpoint-GUID: TfB74bisdmBom1WXjB4-tPfxPcdeJalQ X-Proofpoint-ORIG-GUID: fSEH5H7pwKFZyghH7nTHuMCiubmCCcLs Content-Transfer-Encoding: 8bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 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=2022-05-05_02,2022-05-04_02,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 impostorscore=0 spamscore=0 clxscore=1015 malwarescore=0 adultscore=0 priorityscore=1501 suspectscore=0 bulkscore=0 mlxlogscore=278 phishscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2205050055 Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Wed, 2022-05-04 at 23:31 +0200, Arnd Bergmann wrote: > On Wed, May 4, 2022 at 11:08 PM Bjorn Helgaas wrote: > > On Fri, Apr 29, 2022 at 03:49:59PM +0200, Niklas Schnelle wrote: > > > We introduce a new HAS_IOPORT Kconfig option to indicate support for > > > I/O Port access. In a future patch HAS_IOPORT=n will disable compilation > > > of the I/O accessor functions inb()/outb() and friends on architectures > > > which can not meaningfully support legacy I/O spaces such as s390 or > > > where such support is optional. > > > > So you plan to drop inb()/outb() on architectures where I/O port space > > is optional? So even platforms that have I/O port space may not be > > able to use it? > > > > This feels like a lot of work where the main benefit is to keep > > Kconfig from offering drivers that aren't of interest on s390. > > > > Granted, there may be issues where inb()/outb() does the wrong thing > > such as dereferencing null pointers when I/O port space isn't > > implemented. I think that's a defect in inb()/outb() and could be > > fixed there. > > The current implementation in asm-generic/io.h implements inb()/outb() > using readb()/writeb() with a fixed architecture specific offset. > > There are three possible things that can happen here: > > a) there is a host bridge driver that maps its I/O ports to this window, > and everything works > b) the address range is reserved and accessible but no host bridge > driver has mapped its registers there, so an access causes a > page fault > c) the architecture does not define an offset, and accessing low I/O > ports ends up as a NULL pointer dereference > > The main goal is to avoid c), which is what happens on s390, but > can also happen elsewhere. Catching b) would be nice as well, > but is much harder to do from generic code as you'd need an > architecture specific inline asm statement to insert a ex_table > fixup, or a runtime conditional on each access. > > Arnd Yes and to add to this, we did try a local solution in inb()/outb() before. This added a warning when they are used and we know at compile time that we're dealing with case c). This approach was nacked by Linus though as we were turning a compile time known broken case into a runtime one: https://lore.kernel.org/lkml/CAHk-=wg80je=K7madF4e7WrRNp37e3qh6y10Svhdc7O8SZ_-8g@mail.gmail.com/ I do agree with this assesment and think this is the right™ approach but it is more churn as can be seen by the size of this series. I think longer term it could be valuable though especially if more platforms phase out I/O port support like POWER9 for which this also allows filtering what drivers will never work. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Niklas Schnelle Date: Thu, 05 May 2022 08:10:15 +0000 Subject: Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary Message-Id: List-Id: References: <20220429135108.2781579-2-schnelle@linux.ibm.com> <20220504210840.GA469916@bhelgaas> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: quoted-printable To: Arnd Bergmann , Bjorn Helgaas Cc: 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)" On Wed, 2022-05-04 at 23:31 +0200, Arnd Bergmann wrote: > On Wed, May 4, 2022 at 11:08 PM Bjorn Helgaas wrote: > > On Fri, Apr 29, 2022 at 03:49:59PM +0200, Niklas Schnelle wrote: > > > We introduce a new HAS_IOPORT Kconfig option to indicate support for > > > I/O Port access. In a future patch HAS_IOPORT=3Dn will disable compil= ation > > > of the I/O accessor functions inb()/outb() and friends on architectur= es > > > which can not meaningfully support legacy I/O spaces such as s390 or > > > where such support is optional. > >=20 > > So you plan to drop inb()/outb() on architectures where I/O port space > > is optional? So even platforms that have I/O port space may not be > > able to use it? > >=20 > > This feels like a lot of work where the main benefit is to keep > > Kconfig from offering drivers that aren't of interest on s390. > >=20 > > Granted, there may be issues where inb()/outb() does the wrong thing > > such as dereferencing null pointers when I/O port space isn't > > implemented. I think that's a defect in inb()/outb() and could be > > fixed there. >=20 > The current implementation in asm-generic/io.h implements inb()/outb() > using readb()/writeb() with a fixed architecture specific offset. >=20 > There are three possible things that can happen here: >=20 > a) there is a host bridge driver that maps its I/O ports to this window, > and everything works > b) the address range is reserved and accessible but no host bridge > driver has mapped its registers there, so an access causes a > page fault > c) the architecture does not define an offset, and accessing low I/O > ports ends up as a NULL pointer dereference >=20 > The main goal is to avoid c), which is what happens on s390, but > can also happen elsewhere. Catching b) would be nice as well, > but is much harder to do from generic code as you'd need an > architecture specific inline asm statement to insert a ex_table > fixup, or a runtime conditional on each access. >=20 > Arnd Yes and to add to this, we did try a local solution in inb()/outb() before. This added a warning when they are used and we know at compile time that we're dealing with case c). This approach was nacked by Linus though as we were turning a compile time known broken case into a runtime one: https://lore.kernel.org/lkml/CAHk-=3Dwg80je=3DK7madF4e7WrRNp37e3qh6y10Svhdc= 7O8SZ_-8g@mail.gmail.com/ I do agree with this assesment and think this is the right=E2=84=A2 approach but it is more churn as can be seen by the size of this series. I think longer term it could be valuable though especially if more platforms phase out I/O port support like POWER9 for which this also allows filtering what drivers will never work. 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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: Thu, 05 May 2022 10:10:15 +0200 In-Reply-To: References: <20220429135108.2781579-2-schnelle@linux.ibm.com> <20220504210840.GA469916@bhelgaas> X-Mailer: Evolution 3.28.5 (3.28.5-18.el8) X-TM-AS-GCONF: 00 X-Proofpoint-GUID: TfB74bisdmBom1WXjB4-tPfxPcdeJalQ X-Proofpoint-ORIG-GUID: fSEH5H7pwKFZyghH7nTHuMCiubmCCcLs X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 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=2022-05-05_02,2022-05-04_02,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 impostorscore=0 spamscore=0 clxscore=1015 malwarescore=0 adultscore=0 priorityscore=1501 suspectscore=0 bulkscore=0 mlxlogscore=278 phishscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2205050055 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220505_011207_008494_4FD46E3E X-CRM114-Status: GOOD ( 39.10 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org T24gV2VkLCAyMDIyLTA1LTA0IGF0IDIzOjMxICswMjAwLCBBcm5kIEJlcmdtYW5uIHdyb3RlOgo+ IE9uIFdlZCwgTWF5IDQsIDIwMjIgYXQgMTE6MDggUE0gQmpvcm4gSGVsZ2FhcyA8aGVsZ2Fhc0Br ZXJuZWwub3JnPiB3cm90ZToKPiA+IE9uIEZyaSwgQXByIDI5LCAyMDIyIGF0IDAzOjQ5OjU5UE0g KzAyMDAsIE5pa2xhcyBTY2huZWxsZSB3cm90ZToKPiA+ID4gV2UgaW50cm9kdWNlIGEgbmV3IEhB U19JT1BPUlQgS2NvbmZpZyBvcHRpb24gdG8gaW5kaWNhdGUgc3VwcG9ydCBmb3IKPiA+ID4gSS9P IFBvcnQgYWNjZXNzLiBJbiBhIGZ1dHVyZSBwYXRjaCBIQVNfSU9QT1JUPW4gd2lsbCBkaXNhYmxl IGNvbXBpbGF0aW9uCj4gPiA+IG9mIHRoZSBJL08gYWNjZXNzb3IgZnVuY3Rpb25zIGluYigpL291 dGIoKSBhbmQgZnJpZW5kcyBvbiBhcmNoaXRlY3R1cmVzCj4gPiA+IHdoaWNoIGNhbiBub3QgbWVh bmluZ2Z1bGx5IHN1cHBvcnQgbGVnYWN5IEkvTyBzcGFjZXMgc3VjaCBhcyBzMzkwIG9yCj4gPiA+ IHdoZXJlIHN1Y2ggc3VwcG9ydCBpcyBvcHRpb25hbC4KPiA+IAo+ID4gU28geW91IHBsYW4gdG8g ZHJvcCBpbmIoKS9vdXRiKCkgb24gYXJjaGl0ZWN0dXJlcyB3aGVyZSBJL08gcG9ydCBzcGFjZQo+ ID4gaXMgb3B0aW9uYWw/ICBTbyBldmVuIHBsYXRmb3JtcyB0aGF0IGhhdmUgSS9PIHBvcnQgc3Bh Y2UgbWF5IG5vdCBiZQo+ID4gYWJsZSB0byB1c2UgaXQ/Cj4gPiAKPiA+IFRoaXMgZmVlbHMgbGlr ZSBhIGxvdCBvZiB3b3JrIHdoZXJlIHRoZSBtYWluIGJlbmVmaXQgaXMgdG8ga2VlcAo+ID4gS2Nv bmZpZyBmcm9tIG9mZmVyaW5nIGRyaXZlcnMgdGhhdCBhcmVuJ3Qgb2YgaW50ZXJlc3Qgb24gczM5 MC4KPiA+IAo+ID4gR3JhbnRlZCwgdGhlcmUgbWF5IGJlIGlzc3VlcyB3aGVyZSBpbmIoKS9vdXRi KCkgZG9lcyB0aGUgd3JvbmcgdGhpbmcKPiA+IHN1Y2ggYXMgZGVyZWZlcmVuY2luZyBudWxsIHBv aW50ZXJzIHdoZW4gSS9PIHBvcnQgc3BhY2UgaXNuJ3QKPiA+IGltcGxlbWVudGVkLiAgSSB0aGlu ayB0aGF0J3MgYSBkZWZlY3QgaW4gaW5iKCkvb3V0YigpIGFuZCBjb3VsZCBiZQo+ID4gZml4ZWQg dGhlcmUuCj4gCj4gVGhlIGN1cnJlbnQgaW1wbGVtZW50YXRpb24gaW4gYXNtLWdlbmVyaWMvaW8u aCBpbXBsZW1lbnRzIGluYigpL291dGIoKQo+IHVzaW5nIHJlYWRiKCkvd3JpdGViKCkgd2l0aCBh IGZpeGVkIGFyY2hpdGVjdHVyZSBzcGVjaWZpYyBvZmZzZXQuCj4gCj4gVGhlcmUgYXJlIHRocmVl IHBvc3NpYmxlIHRoaW5ncyB0aGF0IGNhbiBoYXBwZW4gaGVyZToKPiAKPiBhKSB0aGVyZSBpcyBh IGhvc3QgYnJpZGdlIGRyaXZlciB0aGF0IG1hcHMgaXRzIEkvTyBwb3J0cyB0byB0aGlzIHdpbmRv dywKPiAgICAgYW5kIGV2ZXJ5dGhpbmcgd29ya3MKPiBiKSB0aGUgYWRkcmVzcyByYW5nZSBpcyBy ZXNlcnZlZCBhbmQgYWNjZXNzaWJsZSBidXQgbm8gaG9zdCBicmlkZ2UKPiAgICBkcml2ZXIgaGFz IG1hcHBlZCBpdHMgcmVnaXN0ZXJzIHRoZXJlLCBzbyBhbiBhY2Nlc3MgY2F1c2VzIGEKPiAgICBw YWdlIGZhdWx0Cj4gYykgdGhlIGFyY2hpdGVjdHVyZSBkb2VzIG5vdCBkZWZpbmUgYW4gb2Zmc2V0 LCBhbmQgYWNjZXNzaW5nIGxvdyBJL08KPiAgICAgcG9ydHMgZW5kcyB1cCBhcyBhIE5VTEwgcG9p bnRlciBkZXJlZmVyZW5jZQo+IAo+IFRoZSBtYWluIGdvYWwgaXMgdG8gYXZvaWQgYyksIHdoaWNo IGlzIHdoYXQgaGFwcGVucyBvbiBzMzkwLCBidXQKPiBjYW4gYWxzbyBoYXBwZW4gZWxzZXdoZXJl LiBDYXRjaGluZyBiKSB3b3VsZCBiZSBuaWNlIGFzIHdlbGwsCj4gYnV0IGlzIG11Y2ggaGFyZGVy IHRvIGRvIGZyb20gZ2VuZXJpYyBjb2RlIGFzIHlvdSdkIG5lZWQgYW4KPiBhcmNoaXRlY3R1cmUg c3BlY2lmaWMgaW5saW5lIGFzbSBzdGF0ZW1lbnQgdG8gaW5zZXJ0IGEgZXhfdGFibGUKPiBmaXh1 cCwgb3IgYSBydW50aW1lIGNvbmRpdGlvbmFsIG9uIGVhY2ggYWNjZXNzLgo+IAo+ICAgICAgICAg IEFybmQKClllcyBhbmQgdG8gYWRkIHRvIHRoaXMsIHdlIGRpZCB0cnkgYSBsb2NhbCBzb2x1dGlv biBpbiBpbmIoKS9vdXRiKCkKYmVmb3JlLiBUaGlzIGFkZGVkIGEgd2FybmluZyB3aGVuIHRoZXkg YXJlIHVzZWQgYW5kIHdlIGtub3cgYXQgY29tcGlsZQp0aW1lIHRoYXQgd2UncmUgZGVhbGluZyB3 aXRoIGNhc2UgYykuIFRoaXMgYXBwcm9hY2ggd2FzIG5hY2tlZCBieSBMaW51cwp0aG91Z2ggYXMg d2Ugd2VyZSB0dXJuaW5nIGEgY29tcGlsZSB0aW1lIGtub3duIGJyb2tlbiBjYXNlIGludG8gYQpy dW50aW1lIG9uZToKCmh0dHBzOi8vbG9yZS5rZXJuZWwub3JnL2xrbWwvQ0FIay09d2c4MGplPUs3 bWFkRjRlN1dyUk5wMzdlM3FoNnkxMFN2aGRjN084U1pfLThnQG1haWwuZ21haWwuY29tLwoKSSBk byBhZ3JlZSB3aXRoIHRoaXMgYXNzZXNtZW50IGFuZCB0aGluayB0aGlzIGlzIHRoZSByaWdodOKE oiBhcHByb2FjaApidXQgaXQgaXMgbW9yZSBjaHVybiBhcyBjYW4gYmUgc2VlbiBieSB0aGUgc2l6 ZSBvZiB0aGlzIHNlcmllcy4gSSB0aGluawpsb25nZXIgdGVybSBpdCBjb3VsZCBiZSB2YWx1YWJs ZSB0aG91Z2ggZXNwZWNpYWxseSBpZiBtb3JlIHBsYXRmb3JtcwpwaGFzZSBvdXQgSS9PIHBvcnQg c3VwcG9ydCBsaWtlIFBPV0VSOSBmb3Igd2hpY2ggdGhpcyBhbHNvIGFsbG93cwpmaWx0ZXJpbmcg d2hhdCBkcml2ZXJzIHdpbGwgbmV2ZXIgd29yay4KCgpfX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fXwpsaW51eC1yaXNjdiBtYWlsaW5nIGxpc3QKbGludXgtcmlz Y3ZAbGlzdHMuaW5mcmFkZWFkLm9yZwpodHRwOi8vbGlzdHMuaW5mcmFkZWFkLm9yZy9tYWlsbWFu L2xpc3RpbmZvL2xpbnV4LXJpc2N2Cg== 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DF357C433F5 for ; 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Thu, 5 May 2022 08:10:17 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4C65511C050; Thu, 5 May 2022 08:10:17 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7B05911C04A; Thu, 5 May 2022 08:10:15 +0000 (GMT) Received: from sig-9-145-85-251.uk.ibm.com (unknown [9.145.85.251]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 5 May 2022 08:10:15 +0000 (GMT) Message-ID: Subject: Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary From: Niklas Schnelle To: Arnd Bergmann , Bjorn Helgaas Date: Thu, 05 May 2022 10:10:15 +0200 In-Reply-To: References: <20220429135108.2781579-2-schnelle@linux.ibm.com> <20220504210840.GA469916@bhelgaas> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-18.el8) X-TM-AS-GCONF: 00 X-Proofpoint-GUID: TfB74bisdmBom1WXjB4-tPfxPcdeJalQ X-Proofpoint-ORIG-GUID: fSEH5H7pwKFZyghH7nTHuMCiubmCCcLs Content-Transfer-Encoding: 8bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 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=2022-05-05_02,2022-05-04_02,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 impostorscore=0 spamscore=0 clxscore=1015 malwarescore=0 adultscore=0 priorityscore=1501 suspectscore=0 bulkscore=0 mlxlogscore=278 phishscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2205050055 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Rich Felker , "open list:IA64 \(Itanium\) PLATFORM" , "open list:SUPERH" , Catalin Marinas , Dave Hansen , "open list:MIPS" , "James E.J. Bottomley" , "open list:SPARC + UltraSPARC \(sparc/sparc64\)" , "open list:RISC-V ARCHITECTURE" , Will Deacon , linux-arch , Yoshinori Sato , Helge Deller , "maintainer:X86 ARCHITECTURE \(32-BIT AND 64-BIT\)" , Russell King , Ingo Molnar , Geert Uytterhoeven , linux-pci , Matt Turner , Albert Ou , "open list:M68K ARCHITECTURE" , Ivan Kokshaysky , Paul Walmsley , Thomas Gleixner , "moderated list:ARM PORT" , Richard Henderson , Michal Simek , Thomas Bogendoerfer , "open list:PARISC ARCHITECTURE" , Greg Kroah-Hartman , Linux Kernel Mailing List , Palmer Dabbelt , "open list:ALPHA PORT" , Borislav Petkov , "open list:LINUX FOR POWERPC \(32-BIT AND 64-BIT\)" , "David S. Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, 2022-05-04 at 23:31 +0200, Arnd Bergmann wrote: > On Wed, May 4, 2022 at 11:08 PM Bjorn Helgaas wrote: > > On Fri, Apr 29, 2022 at 03:49:59PM +0200, Niklas Schnelle wrote: > > > We introduce a new HAS_IOPORT Kconfig option to indicate support for > > > I/O Port access. In a future patch HAS_IOPORT=n will disable compilation > > > of the I/O accessor functions inb()/outb() and friends on architectures > > > which can not meaningfully support legacy I/O spaces such as s390 or > > > where such support is optional. > > > > So you plan to drop inb()/outb() on architectures where I/O port space > > is optional? So even platforms that have I/O port space may not be > > able to use it? > > > > This feels like a lot of work where the main benefit is to keep > > Kconfig from offering drivers that aren't of interest on s390. > > > > Granted, there may be issues where inb()/outb() does the wrong thing > > such as dereferencing null pointers when I/O port space isn't > > implemented. I think that's a defect in inb()/outb() and could be > > fixed there. > > The current implementation in asm-generic/io.h implements inb()/outb() > using readb()/writeb() with a fixed architecture specific offset. > > There are three possible things that can happen here: > > a) there is a host bridge driver that maps its I/O ports to this window, > and everything works > b) the address range is reserved and accessible but no host bridge > driver has mapped its registers there, so an access causes a > page fault > c) the architecture does not define an offset, and accessing low I/O > ports ends up as a NULL pointer dereference > > The main goal is to avoid c), which is what happens on s390, but > can also happen elsewhere. Catching b) would be nice as well, > but is much harder to do from generic code as you'd need an > architecture specific inline asm statement to insert a ex_table > fixup, or a runtime conditional on each access. > > Arnd Yes and to add to this, we did try a local solution in inb()/outb() before. This added a warning when they are used and we know at compile time that we're dealing with case c). This approach was nacked by Linus though as we were turning a compile time known broken case into a runtime one: https://lore.kernel.org/lkml/CAHk-=wg80je=K7madF4e7WrRNp37e3qh6y10Svhdc7O8SZ_-8g@mail.gmail.com/ I do agree with this assesment and think this is the right™ approach but it is more churn as can be seen by the size of this series. I think longer term it could be valuable though especially if more platforms phase out I/O port support like POWER9 for which this also allows filtering what drivers will never work. 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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: Thu, 05 May 2022 10:10:15 +0200 In-Reply-To: References: <20220429135108.2781579-2-schnelle@linux.ibm.com> <20220504210840.GA469916@bhelgaas> X-Mailer: Evolution 3.28.5 (3.28.5-18.el8) X-TM-AS-GCONF: 00 X-Proofpoint-GUID: TfB74bisdmBom1WXjB4-tPfxPcdeJalQ X-Proofpoint-ORIG-GUID: fSEH5H7pwKFZyghH7nTHuMCiubmCCcLs X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 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=2022-05-05_02,2022-05-04_02,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 impostorscore=0 spamscore=0 clxscore=1015 malwarescore=0 adultscore=0 priorityscore=1501 suspectscore=0 bulkscore=0 mlxlogscore=278 phishscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2205050055 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220505_011207_008494_4FD46E3E X-CRM114-Status: GOOD ( 39.10 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org T24gV2VkLCAyMDIyLTA1LTA0IGF0IDIzOjMxICswMjAwLCBBcm5kIEJlcmdtYW5uIHdyb3RlOgo+ IE9uIFdlZCwgTWF5IDQsIDIwMjIgYXQgMTE6MDggUE0gQmpvcm4gSGVsZ2FhcyA8aGVsZ2Fhc0Br ZXJuZWwub3JnPiB3cm90ZToKPiA+IE9uIEZyaSwgQXByIDI5LCAyMDIyIGF0IDAzOjQ5OjU5UE0g KzAyMDAsIE5pa2xhcyBTY2huZWxsZSB3cm90ZToKPiA+ID4gV2UgaW50cm9kdWNlIGEgbmV3IEhB U19JT1BPUlQgS2NvbmZpZyBvcHRpb24gdG8gaW5kaWNhdGUgc3VwcG9ydCBmb3IKPiA+ID4gSS9P IFBvcnQgYWNjZXNzLiBJbiBhIGZ1dHVyZSBwYXRjaCBIQVNfSU9QT1JUPW4gd2lsbCBkaXNhYmxl IGNvbXBpbGF0aW9uCj4gPiA+IG9mIHRoZSBJL08gYWNjZXNzb3IgZnVuY3Rpb25zIGluYigpL291 dGIoKSBhbmQgZnJpZW5kcyBvbiBhcmNoaXRlY3R1cmVzCj4gPiA+IHdoaWNoIGNhbiBub3QgbWVh bmluZ2Z1bGx5IHN1cHBvcnQgbGVnYWN5IEkvTyBzcGFjZXMgc3VjaCBhcyBzMzkwIG9yCj4gPiA+ IHdoZXJlIHN1Y2ggc3VwcG9ydCBpcyBvcHRpb25hbC4KPiA+IAo+ID4gU28geW91IHBsYW4gdG8g ZHJvcCBpbmIoKS9vdXRiKCkgb24gYXJjaGl0ZWN0dXJlcyB3aGVyZSBJL08gcG9ydCBzcGFjZQo+ ID4gaXMgb3B0aW9uYWw/ICBTbyBldmVuIHBsYXRmb3JtcyB0aGF0IGhhdmUgSS9PIHBvcnQgc3Bh Y2UgbWF5IG5vdCBiZQo+ID4gYWJsZSB0byB1c2UgaXQ/Cj4gPiAKPiA+IFRoaXMgZmVlbHMgbGlr ZSBhIGxvdCBvZiB3b3JrIHdoZXJlIHRoZSBtYWluIGJlbmVmaXQgaXMgdG8ga2VlcAo+ID4gS2Nv bmZpZyBmcm9tIG9mZmVyaW5nIGRyaXZlcnMgdGhhdCBhcmVuJ3Qgb2YgaW50ZXJlc3Qgb24gczM5 MC4KPiA+IAo+ID4gR3JhbnRlZCwgdGhlcmUgbWF5IGJlIGlzc3VlcyB3aGVyZSBpbmIoKS9vdXRi KCkgZG9lcyB0aGUgd3JvbmcgdGhpbmcKPiA+IHN1Y2ggYXMgZGVyZWZlcmVuY2luZyBudWxsIHBv aW50ZXJzIHdoZW4gSS9PIHBvcnQgc3BhY2UgaXNuJ3QKPiA+IGltcGxlbWVudGVkLiAgSSB0aGlu ayB0aGF0J3MgYSBkZWZlY3QgaW4gaW5iKCkvb3V0YigpIGFuZCBjb3VsZCBiZQo+ID4gZml4ZWQg dGhlcmUuCj4gCj4gVGhlIGN1cnJlbnQgaW1wbGVtZW50YXRpb24gaW4gYXNtLWdlbmVyaWMvaW8u aCBpbXBsZW1lbnRzIGluYigpL291dGIoKQo+IHVzaW5nIHJlYWRiKCkvd3JpdGViKCkgd2l0aCBh IGZpeGVkIGFyY2hpdGVjdHVyZSBzcGVjaWZpYyBvZmZzZXQuCj4gCj4gVGhlcmUgYXJlIHRocmVl IHBvc3NpYmxlIHRoaW5ncyB0aGF0IGNhbiBoYXBwZW4gaGVyZToKPiAKPiBhKSB0aGVyZSBpcyBh IGhvc3QgYnJpZGdlIGRyaXZlciB0aGF0IG1hcHMgaXRzIEkvTyBwb3J0cyB0byB0aGlzIHdpbmRv dywKPiAgICAgYW5kIGV2ZXJ5dGhpbmcgd29ya3MKPiBiKSB0aGUgYWRkcmVzcyByYW5nZSBpcyBy ZXNlcnZlZCBhbmQgYWNjZXNzaWJsZSBidXQgbm8gaG9zdCBicmlkZ2UKPiAgICBkcml2ZXIgaGFz IG1hcHBlZCBpdHMgcmVnaXN0ZXJzIHRoZXJlLCBzbyBhbiBhY2Nlc3MgY2F1c2VzIGEKPiAgICBw YWdlIGZhdWx0Cj4gYykgdGhlIGFyY2hpdGVjdHVyZSBkb2VzIG5vdCBkZWZpbmUgYW4gb2Zmc2V0 LCBhbmQgYWNjZXNzaW5nIGxvdyBJL08KPiAgICAgcG9ydHMgZW5kcyB1cCBhcyBhIE5VTEwgcG9p bnRlciBkZXJlZmVyZW5jZQo+IAo+IFRoZSBtYWluIGdvYWwgaXMgdG8gYXZvaWQgYyksIHdoaWNo IGlzIHdoYXQgaGFwcGVucyBvbiBzMzkwLCBidXQKPiBjYW4gYWxzbyBoYXBwZW4gZWxzZXdoZXJl LiBDYXRjaGluZyBiKSB3b3VsZCBiZSBuaWNlIGFzIHdlbGwsCj4gYnV0IGlzIG11Y2ggaGFyZGVy IHRvIGRvIGZyb20gZ2VuZXJpYyBjb2RlIGFzIHlvdSdkIG5lZWQgYW4KPiBhcmNoaXRlY3R1cmUg c3BlY2lmaWMgaW5saW5lIGFzbSBzdGF0ZW1lbnQgdG8gaW5zZXJ0IGEgZXhfdGFibGUKPiBmaXh1 cCwgb3IgYSBydW50aW1lIGNvbmRpdGlvbmFsIG9uIGVhY2ggYWNjZXNzLgo+IAo+ICAgICAgICAg IEFybmQKClllcyBhbmQgdG8gYWRkIHRvIHRoaXMsIHdlIGRpZCB0cnkgYSBsb2NhbCBzb2x1dGlv biBpbiBpbmIoKS9vdXRiKCkKYmVmb3JlLiBUaGlzIGFkZGVkIGEgd2FybmluZyB3aGVuIHRoZXkg YXJlIHVzZWQgYW5kIHdlIGtub3cgYXQgY29tcGlsZQp0aW1lIHRoYXQgd2UncmUgZGVhbGluZyB3 aXRoIGNhc2UgYykuIFRoaXMgYXBwcm9hY2ggd2FzIG5hY2tlZCBieSBMaW51cwp0aG91Z2ggYXMg d2Ugd2VyZSB0dXJuaW5nIGEgY29tcGlsZSB0aW1lIGtub3duIGJyb2tlbiBjYXNlIGludG8gYQpy dW50aW1lIG9uZToKCmh0dHBzOi8vbG9yZS5rZXJuZWwub3JnL2xrbWwvQ0FIay09d2c4MGplPUs3 bWFkRjRlN1dyUk5wMzdlM3FoNnkxMFN2aGRjN084U1pfLThnQG1haWwuZ21haWwuY29tLwoKSSBk byBhZ3JlZSB3aXRoIHRoaXMgYXNzZXNtZW50IGFuZCB0aGluayB0aGlzIGlzIHRoZSByaWdodOKE oiBhcHByb2FjaApidXQgaXQgaXMgbW9yZSBjaHVybiBhcyBjYW4gYmUgc2VlbiBieSB0aGUgc2l6 ZSBvZiB0aGlzIHNlcmllcy4gSSB0aGluawpsb25nZXIgdGVybSBpdCBjb3VsZCBiZSB2YWx1YWJs ZSB0aG91Z2ggZXNwZWNpYWxseSBpZiBtb3JlIHBsYXRmb3JtcwpwaGFzZSBvdXQgSS9PIHBvcnQg c3VwcG9ydCBsaWtlIFBPV0VSOSBmb3Igd2hpY2ggdGhpcyBhbHNvIGFsbG93cwpmaWx0ZXJpbmcg d2hhdCBkcml2ZXJzIHdpbGwgbmV2ZXIgd29yay4KCgpfX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fXwpsaW51eC1hcm0ta2VybmVsIG1haWxpbmcgbGlzdApsaW51 eC1hcm0ta2VybmVsQGxpc3RzLmluZnJhZGVhZC5vcmcKaHR0cDovL2xpc3RzLmluZnJhZGVhZC5v cmcvbWFpbG1hbi9saXN0aW5mby9saW51eC1hcm0ta2VybmVsCg==