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Wed, 28 Oct 2020 09:43:54 +0000 (GMT) Subject: Re: [PATCH v2 2/2] ARM: move device tree mapping out of linear region To: Ard Biesheuvel Cc: Linux ARM , Linux Samsung SOC , Krzysztof Kozlowski , Florian Fainelli , Nicolas Pitre , Linus Walleij , Russell King , Rob Herring From: Marek Szyprowski Message-ID: Date: Wed, 28 Oct 2020 10:43:54 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: Content-Transfer-Encoding: 7bit Content-Language: en-US X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrNKsWRmVeSWpSXmKPExsWy7djPc7rRtjPjDeZuYrL4+eU9o8Wvd0fY Lc6f38BuMeXPciaLTY+vsVrMOL+PyeLQ1L2MFvNevGCzaN17hN2B0+PytYvMHs9OtLN57Jx1 l91j06pONo871/aweWxeUu/xeZNcAHsUl01Kak5mWWqRvl0CV8b/h7dYCv4KV9xZmdHAOFWg i5GDQ0LAROLz1uQuRi4OIYEVjBL7HneyQzhfGCU27WgHcjiBnM+MElM2aME07OqLhKhZzijx or0VquE9o8SupdtYQRqEBQIk3r+YwAJiiwioSPxoessIYjMLXGeS6N8pCWKzCRhKdL3tYgOx eQXsJOZ82gZWzyKgKvFp+mOwelGBJIm/n/8wQ9QISpyc+QSshlMgUOLYgR1MEDPlJba/ncMM YYtL3HoynwnkIAmBc+wSUz6cBFsgIeAiMeHmLUYIW1ji1fEt7BC2jMTpyT0sEA3NjBIPz61l h3B6GCUuN82A6rCWuHPuFxvI/8wCmhLrd+lDhB0ljjTcZIYEC5/EjbeCEEfwSUzaNh0qzCvR 0SYEUa0mMev4Ori1By9cYp7AqDQLyWuzkLwzC8k7sxD2LmBkWcUonlpanJueWmyUl1quV5yY W1yal66XnJ+7iRGYpE7/O/5lB+OuP0mHGAU4GJV4eG8ozIgXYk0sK67MPcQowcGsJMLrdPZ0 nBBvSmJlVWpRfnxRaU5q8SFGaQ4WJXFe40UvY4UE0hNLUrNTUwtSi2CyTBycUg2MoUctO5/k susemzBtm9z24ytCFDR0ta51LZzDeOxw4JywuA3sLD4rzENymdcdP3DsoO06exc1RWsPW/Gw +qkM96dn89nIp1S+maj053Fs5qoZd64t3My+uXV5g6jKvyzZP8UJijvXZeR7pa1YtaBlKpNv 5K7PRocf/E4wLzDjnXpgvqtK/r4SJZbijERDLeai4kQAv4rT6U4DAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrAIsWRmVeSWpSXmKPExsVy+t/xu7pRtjPjDbruK1j8/PKe0eLXuyPs FufPb2C3mPJnOZPFpsfXWC1mnN/HZHFo6l5Gi3kvXrBZtO49wu7A6XH52kVmj2cn2tk8ds66 y+6xaVUnm8eda3vYPDYvqff4vEkugD1Kz6Yov7QkVSEjv7jEVina0MJIz9DSQs/IxFLP0Ng8 1srIVEnfziYlNSezLLVI3y5BL+P/w1ssBX+FK+6szGhgnCrQxcjBISFgIrGrL7KLkYtDSGAp o0TrtvOsXYycQHEZiZPTGqBsYYk/17rYIIreMkrsWXuSESQhLOAnsXrvT7AiEQEViR9NbxlB ipgFbjJJbJjWxw7R8Y1JoqltHVgHm4ChRNdbkFGcHLwCdhJzPm1jAbFZBFQlPk1/DFYjKpAk 8fLCVCaIGkGJkzOfgNVwCgRKHDuwAyzOLGAmMW/zQ2YIW15i+9s5ULa4xK0n85kmMArNQtI+ C0nLLCQts5C0LGBkWcUoklpanJueW2yoV5yYW1yal66XnJ+7iREYm9uO/dy8g/HSxuBDjAIc jEo8vDcUZsQLsSaWFVfmHmKU4GBWEuF1Ons6Tog3JbGyKrUoP76oNCe1+BCjKdBzE5mlRJPz gWkjryTe0NTQ3MLS0NzY3NjMQkmct0PgYIyQQHpiSWp2ampBahFMHxMHp1QD45T8EylaO5iZ 1vN8b5DZferw+d+r9k3Kqfhpmn/d49aR732TXBmLXW2z1L29tfPnH58RZvJ75hveYy/5DpUd aVY5Mu9iblvnP+6vPMl7ukLK697yWt2cH/J2TpummFFW/oz/7btmVrF+e6yi6CI7Zb46++e7 7i6znpl1pmyRW3vl2aVz+8I0ZZRYijMSDbWYi4oTAYUz6srjAgAA X-CMS-MailID: 20201028094354eucas1p276bc31d7b0caa105886af742b7100d4e X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20201028091912eucas1p13fb9cd947faa6bfd79199ea79648b6af X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20201028091912eucas1p13fb9cd947faa6bfd79199ea79648b6af References: <20201007083944.27910-1-ardb@kernel.org> <20201007083944.27910-3-ardb@kernel.org> <920965b8-6f87-3f82-9fce-d3051fc543ca@samsung.com> Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org Hi Ard, On 28.10.2020 10:24, Ard Biesheuvel wrote: > On Wed, 28 Oct 2020 at 10:22, Ard Biesheuvel wrote: >> On Wed, 28 Oct 2020 at 10:19, Marek Szyprowski wrote: >>> On 07.10.2020 10:39, Ard Biesheuvel wrote: >>>> On ARM, setting up the linear region is tricky, given the constraints >>>> around placement and alignment of the memblocks, and how the kernel >>>> itself as well as the DT are placed in physical memory. >>>> >>>> Let's simplify matters a bit, by moving the device tree mapping to the >>>> top of the address space, right between the end of the vmalloc region >>>> and the start of the the fixmap region, and create a read-only mapping >>>> for it that is independent of the size of the linear region, and how it >>>> is organized. >>>> >>>> Since this region was formerly used as a guard region, which will now be >>>> populated fully on LPAE builds by this read-only mapping (which will >>>> still be able to function as a guard region for stray writes), bump the >>>> start of the [underutilized] fixmap region by 512 KB as well, to ensure >>>> that there is always a proper guard region here. Doing so still leaves >>>> ample room for the fixmap space, even with NR_CPUS set to its maximum >>>> value of 32. >>>> >>>> Tested-by: Linus Walleij >>>> Reviewed-by: Linus Walleij >>>> Signed-off-by: Ard Biesheuvel >>> This patch landed in linux-next 20201028 as commit 7a1be318f579 ("ARM: >>> 9012/1: move device tree mapping out of linear region"). Sadly it broke >>> booting almost all Samsung Exynos-based boards. The only one which >>> booted, used an appended device tree. I can provide more information if >>> needed, just let me know what to check. "Starting kernel ..." is the >>> last message I see here. No output from earlycon. >>> >> Thanks for the report. I will have a look later today. >> >> Do these platforms happen to have any static device mappings that may >> collide with this mapping of the FDT? Also, could this be related to >> device drivers making changes in memory to the FDT image? Because the >> permanent mapping of the FDT is read-only now. >> > IOW, does using MT_MEMORY_RW instead of MT_ROM for the mapping make a > difference? Nope, chaning it to MT_MEMORY_RW doesn't fix anything. The only static mapping I'm aware is S5P_VA_CHIPID at 0xF6000000 + 0x02000000. 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Ard, On 28.10.2020 10:24, Ard Biesheuvel wrote: > On Wed, 28 Oct 2020 at 10:22, Ard Biesheuvel wrote: >> On Wed, 28 Oct 2020 at 10:19, Marek Szyprowski wrote: >>> On 07.10.2020 10:39, Ard Biesheuvel wrote: >>>> On ARM, setting up the linear region is tricky, given the constraints >>>> around placement and alignment of the memblocks, and how the kernel >>>> itself as well as the DT are placed in physical memory. >>>> >>>> Let's simplify matters a bit, by moving the device tree mapping to the >>>> top of the address space, right between the end of the vmalloc region >>>> and the start of the the fixmap region, and create a read-only mapping >>>> for it that is independent of the size of the linear region, and how it >>>> is organized. >>>> >>>> Since this region was formerly used as a guard region, which will now be >>>> populated fully on LPAE builds by this read-only mapping (which will >>>> still be able to function as a guard region for stray writes), bump the >>>> start of the [underutilized] fixmap region by 512 KB as well, to ensure >>>> that there is always a proper guard region here. Doing so still leaves >>>> ample room for the fixmap space, even with NR_CPUS set to its maximum >>>> value of 32. >>>> >>>> Tested-by: Linus Walleij >>>> Reviewed-by: Linus Walleij >>>> Signed-off-by: Ard Biesheuvel >>> This patch landed in linux-next 20201028 as commit 7a1be318f579 ("ARM: >>> 9012/1: move device tree mapping out of linear region"). Sadly it broke >>> booting almost all Samsung Exynos-based boards. The only one which >>> booted, used an appended device tree. I can provide more information if >>> needed, just let me know what to check. "Starting kernel ..." is the >>> last message I see here. No output from earlycon. >>> >> Thanks for the report. I will have a look later today. >> >> Do these platforms happen to have any static device mappings that may >> collide with this mapping of the FDT? Also, could this be related to >> device drivers making changes in memory to the FDT image? Because the >> permanent mapping of the FDT is read-only now. >> > IOW, does using MT_MEMORY_RW instead of MT_ROM for the mapping make a > difference? Nope, chaning it to MT_MEMORY_RW doesn't fix anything. The only static mapping I'm aware is S5P_VA_CHIPID at 0xF6000000 + 0x02000000. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel