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X-Received-From: 2607:f8b0:4864:20::244 Subject: Re: [Qemu-devel] [PATCH v7 00/42] Invert Endian bit in SPARCv9 MMU TTE X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: KONRAD Frederic , Alberto Garcia , Qemu-block , Aleksandar Rikalo , Halil Pasic , =?UTF-8?Q?Herv=C3=A9_Poussineau?= , Anthony PERARD , "open list:X86" , Laszlo Ersek , Jason Wang , =?UTF-8?B?SmnFmcOtIFDDrXJrbw==?= , Eduardo Habkost , Beniamino Galvani , Eric Auger , Alex Williamson , Stefan Hajnoczi , John Snow , Richard Henderson , Kevin Wolf , Andrew Jeffery , claudio.fontana@suse.com, Chris Wulff , Laurent Vivier , sundeep subbaraya , Michael Walle , qemu-ppc , Bastian Koppelmann , Igor Mammedov , Fam Zheng , David Hildenbrand , Palmer Dabbelt , Keith Busch , Max Filippov , Hannes Reinecke , Stefano Stabellini , Andrey Smirnov , Helge Deller , Magnus Damm , Artyom Tarasenko , Corey Minyard , Stefan Weil , Yuval Shaia , qemu-s390x , qemu-arm , Jan Kiszka , =?UTF-8?Q?C=C3=A9dric_Le_Goater?= , Stafford Horne , "open list:RISC-V" , Igor Mitsyanko , Cornelia Huck , =?UTF-8?Q?Philippe_Mathieu=2DDaud=C3=A9?= , Aleksandar Markovic , Peter Chubb , Aurelien Jarno , Paul Burton , Sagar Karandikar , Anthony Green , Gerd Hoffmann , "Edgar E. Iglesias" , Guan Xuetao , Rob Herring , Christian Borntraeger , Joel Stanley , Antony Pavlov , Fabien Chouteau , Andrew Baumann , Max Reitz , Collin Walling , Dmitry Fleytman , "Michael S. Tsirkin" , Mark Cave-Ayland , QEMU Developers , Jiri Slaby , Marek Vasut , Jia Liu , =?UTF-8?B?TWFyYy1BbmRyw6kgTHVyZWF1?= , Alistair Francis , Paul Durrant , David Gibson , Xiao Guangrong , Thomas Huth , Jean-Christophe DUBOIS , Paolo Bonzini , Stefan Berger Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, 16 Aug 2019 at 12:37, wrote: > > Hi Phillippe, > > On 8/16/19 7:58 PM, Philippe Mathieu-Daud=C3=A9 wrote: > >On 8/16/19 8:28 AM, tony.nguyen@bt.com wrote: > >> For each device declared with DEVICE_NATIVE_ENDIAN, find the set of > >> targets from the set of target/hw/*/device.o. > >> > >> If the set of targets are all little or all big endian, re-declare > >> the device endianness as DEVICE_LITTLE_ENDIAN or DEVICE_BIG_ENDIAN > >> respectively. > > > >If only little endian targets use a device, that doesn't mean the device > >is designed in little endian... > > > >Then if a big endian target plan to use this device, it will require > >more work and you might have introduced regressions... > > > >I'm not sure this is a safe move. > > > >> This *naive* deduction may result in genuinely native endian devices > >> being incorrectly declared as little or big endian, but should not > >> introduce regressions for current targets. > > > > Roger. Evidently too naive. TBH, most devices I've never heard of... OTOH it's worth noting that it's quite likely that most of the implementations of these DEVICE_NATIVE_ENDIAN devices picked it in an equally naive way, by just copying some other device's code... thanks -- PMM 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=-0.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 2ED84C3A59C for ; Fri, 16 Aug 2019 12:02:51 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EF11C2086C for ; Fri, 16 Aug 2019 12:02:50 +0000 (UTC) Authentication-Results: mail.kernel.org; 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Fri, 16 Aug 2019 05:02:14 -0700 (PDT) MIME-Version: 1.0 References: <43bc5e07ac614d0e8e740bf6007ff77b@tpw09926dag18e.domain1.systemhost.net> <1565955445398.83897@bt.com> In-Reply-To: <1565955445398.83897@bt.com> From: Peter Maydell Date: Fri, 16 Aug 2019 13:02:03 +0100 Message-ID: To: tony.nguyen@bt.com Subject: Re: [Xen-devel] [Qemu-devel] [PATCH v7 00/42] Invert Endian bit in SPARCv9 MMU TTE X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: KONRAD Frederic , Alberto Garcia , Qemu-block , Aleksandar Rikalo , Halil Pasic , =?UTF-8?Q?Herv=C3=A9_Poussineau?= , Anthony PERARD , "open list:X86" , Laszlo Ersek , Jason Wang , =?UTF-8?B?SmnFmcOtIFDDrXJrbw==?= , Eduardo Habkost , Beniamino Galvani , Eric Auger , Alex Williamson , Stefan Hajnoczi , John Snow , Richard Henderson , Kevin Wolf , Andrew Jeffery , claudio.fontana@suse.com, Chris Wulff , Laurent Vivier , sundeep subbaraya , Michael Walle , qemu-ppc , Bastian Koppelmann , Igor Mammedov , Fam Zheng , David Hildenbrand , Palmer Dabbelt , BALATON Zoltan , Keith Busch , Max Filippov , Hannes Reinecke , Stefano Stabellini , Andrey Smirnov , Helge Deller , Magnus Damm , Marcel Apfelbaum , Artyom Tarasenko , Corey Minyard , Stefan Weil , Yuval Shaia , qemu-s390x , qemu-arm , Jan Kiszka , =?UTF-8?Q?C=C3=A9dric_Le_Goater?= , Stafford Horne , "open list:RISC-V" , Igor Mitsyanko , Cornelia Huck , =?UTF-8?Q?Philippe_Mathieu=2DDaud=C3=A9?= , Aleksandar Markovic , Peter Chubb , Aurelien Jarno , Paul Burton , Sagar Karandikar , Anthony Green , Gerd Hoffmann , "Edgar E. Iglesias" , Guan Xuetao , Rob Herring , Christian Borntraeger , Joel Stanley , Antony Pavlov , Fabien Chouteau , andrzej zaborowski , Andrew Baumann , Max Reitz , Collin Walling , Dmitry Fleytman , "Michael S. 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Tsirkin" , Igor Mammedov , Marcel Apfelbaum , Xiao Guangrong , Alistair Francis , Beniamino Galvani , =?UTF-8?Q?C=C3=A9dric_Le_Goater?= , Andrew Jeffery , Joel Stanley , Igor Mitsyanko , Rob Herring , Peter Chubb , sundeep subbaraya , Jan Kiszka , andrzej zaborowski , Eric Auger , Gerd Hoffmann , Michael Walle , Kevin Wolf , Max Reitz , John Snow , Keith Busch , =?UTF-8?B?TWFyYy1BbmRyw6kgTHVyZWF1?= , Andrew Baumann , "Edgar E. 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X-Received-From: 2607:f8b0:4864:20::244 Subject: Re: [Qemu-riscv] [Qemu-devel] [PATCH v7 00/42] Invert Endian bit in SPARCv9 MMU TTE X-BeenThere: qemu-riscv@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 16 Aug 2019 12:02:18 -0000 On Fri, 16 Aug 2019 at 12:37, wrote: > > Hi Phillippe, > > On 8/16/19 7:58 PM, Philippe Mathieu-Daud=C3=A9 wrote: > >On 8/16/19 8:28 AM, tony.nguyen@bt.com wrote: > >> For each device declared with DEVICE_NATIVE_ENDIAN, find the set of > >> targets from the set of target/hw/*/device.o. > >> > >> If the set of targets are all little or all big endian, re-declare > >> the device endianness as DEVICE_LITTLE_ENDIAN or DEVICE_BIG_ENDIAN > >> respectively. > > > >If only little endian targets use a device, that doesn't mean the device > >is designed in little endian... > > > >Then if a big endian target plan to use this device, it will require > >more work and you might have introduced regressions... > > > >I'm not sure this is a safe move. > > > >> This *naive* deduction may result in genuinely native endian devices > >> being incorrectly declared as little or big endian, but should not > >> introduce regressions for current targets. > > > > Roger. Evidently too naive. TBH, most devices I've never heard of... OTOH it's worth noting that it's quite likely that most of the implementations of these DEVICE_NATIVE_ENDIAN devices picked it in an equally naive way, by just copying some other device's code... thanks -- PMM