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Tue, 15 Oct 2019 15:06:44 -0700 (PDT) Subject: Re: [PATCH v2 1/5] ARC: mm: remove __ARCH_USE_5LEVEL_HACK To: Linus Torvalds References: <20191015191926.9281-1-vgupta@synopsys.com> <20191015191926.9281-2-vgupta@synopsys.com> From: Vineet Gupta Openpgp: preference=signencrypt Autocrypt: addr=vineetg76@gmail.com; prefer-encrypt=mutual; keydata= mQINBFEffBMBEADIXSn0fEQcM8GPYFZyvBrY8456hGplRnLLFimPi/BBGFA24IR+B/Vh/EFk B5LAyKuPEEbR3WSVB1x7TovwEErPWKmhHFbyugdCKDv7qWVj7pOB+vqycTG3i16eixB69row lDkZ2RQyy1i/wOtHt8Kr69V9aMOIVIlBNjx5vNOjxfOLux3C0SRl1veA8sdkoSACY3McOqJ8 zR8q1mZDRHCfz+aNxgmVIVFN2JY29zBNOeCzNL1b6ndjU73whH/1hd9YMx2Sp149T8MBpkuQ cFYUPYm8Mn0dQ5PHAide+D3iKCHMupX0ux1Y6g7Ym9jhVtxq3OdUI5I5vsED7NgV9c8++baM 7j7ext5v0l8UeulHfj4LglTaJIvwbUrCGgtyS9haKlUHbmey/af1j0sTrGxZs1ky1cTX7yeF nSYs12GRiVZkh/Pf3nRLkjV+kH++ZtR1GZLqwamiYZhAHjo1Vzyl50JT9EuX07/XTyq/Bx6E dcJWr79ZphJ+mR2HrMdvZo3VSpXEgjROpYlD4GKUApFxW6RrZkvMzuR2bqi48FThXKhFXJBd JiTfiO8tpXaHg/yh/V9vNQqdu7KmZIuZ0EdeZHoXe+8lxoNyQPcPSj7LcmE6gONJR8ZqAzyk F5voeRIy005ZmJJ3VOH3Gw6Gz49LVy7Kz72yo1IPHZJNpSV5xwARAQABtC1WaW5lZXQgR3Vw dGEgKHBlcnNvbmFsKSA8dmluZWV0Zzc2QGdtYWlsLmNvbT6JAj4EEwECACgCGwMGCwkIBwMC BhUIAgkKCwQWAgMBAh4BAheABQJdcAXyBQkVtotfAAoJEGnX8d3iisJeH6EP/ip0xGS2DNI4 2za/eRU85Kc+wQhz/NWhDMCl3xWzKLBO4SaOMlfp7j4vgogj7ufok7I7Ke0Tvww9kbk+vgeg ERlcGd+OczDX4ze4EabgW5z8sMax84yqd/4HVJBORGtjR5uXh0fugKrTBGA5AJMf/qGyyHZX 8vemIm7gQK7aUgkKId9D4O1wIdgrUdvg8ocFw9a1TWv6s3keyJNfqKKwSNdywKbVdkMFjLcL d6jHP9ice59Fkh4Lhte6DfDx4gjbhF1gyoqSL/JvaBLYJTdkl2tGzM/CYSqOsivUH9//X5uT ijG3mkIqb//7H1ab/zgF0/9jxjhtiKYwl71NN9Zm2rJiGegLxv61RjEZT2oEacZXIyXqZSh/ vz8rWOBAr1EE76XzqC5TC6qa5Xdo2Q9g5d9p7pkQ9WFfDAQujrB8qZIS6IwhFPSZQIGUWB5x F/CskhsxXOgPL0isSv6a5OB2jd3G78/o7GfDSaiOVzgL4hx4gIY0aQqANuNlLC8q55fYquMS lO4FqcpaK5yt81uzPTv8HetA1577Yeur9aPjgZpqHI35f6V7uQdDRQlI8kmkm/ceWAxbliR3 YjH32HRGpOc6Z3q1gGSruPnpjeSRVjb8GJGEIWLbhcyF/kRV6T6vcER3x4LaBnmU17uE5vw4 789n0dLVksMviHzcGg1/8WUvuQINBFEffBMBEADXZ2pWw4Regpfw+V+Vr6tvZFRl245PV9rW FU72xNuvZKq/WE3xMu+ZE7l2JKpSjrEoeOHejtT0cILeQ/Yhf2t2xAlrBLlGOMmMYKK/K0Dc 2zf0MiPRbW/NCivMbGRZdhAAMx1bpVhInKjU/6/4mT7gcE57Ep0tl3HBfpxCK8RRlZc3v8BH OaEfcWSQD7QNTZK/kYJo+Oyux+fzyM5TTuKAaVE63NHCgWtFglH2vt2IyJ1XoPkAMueLXay6 enSKNci7qAG2UwicyVDCK9AtEub+ps8NakkeqdSkDRp5tQldJbfDaMXuWxJuPjfSojHIAbFq P6QaANXvTCSuBgkmGZ58skeNopasrJA4z7OsKRUBvAnharU82HGemtIa4Z83zotOGNdaBBOH NN2MHyfGLm+kEoccQheH+my8GtbH1a8eRBtxlk4c02ONkq1Vg1EbIzvgi4a56SrENFx4+4sZ cm8oItShAoKGIE/UCkj/jPlWqOcM/QIqJ2bR8hjBny83ONRf2O9nJuEYw9vZAPFViPwWG8tZ 7J+ReuXKai4DDr+8oFOi/40mIDe/Bat3ftyd+94Z1RxDCngd3Q85bw13t2ttNLw5eHufLIpo EyAhTCLNQ58eT91YGVGvFs39IuH0b8ovVvdkKGInCT59Vr0MtfgcsqpDxWQXJXYZYTFHd3/R swARAQABiQIlBBgBAgAPAhsMBQJdcAYOBQkVtot7AAoJEGnX8d3iisJeCGAP/0QNMvc0QfIq z7CzZWSai8s74YxxzNRwTigxgx0YjHFYWDd6sYYdhqFSjeQ6p//QB5Uu+5YByzM2nHiDH0ys cL0iTZIz3IEq/IL65SNShdpUrzD3mB/gS95IYxBcicRXXFA7gdYDYmX86fjqJO2dCAhdO2l/ BHSi6KOaM6BofxwQz5189/NsxuF03JplqLgUgkpKWYJxkx9+CsQL+gruDc1iS9BFJ6xoXosS 2ieZYflNGvslk1pyePM7miK5BaMZcpvJ/i50rQBUEnYi0jGeXxgbMSuLy/KiNLcmkKucaRO+ h2g0nxEADaPezfg5yBrUYCvJy+dIO5y2wS80ayO16yxkknlN1y4GuLVSj4vmJWiT6DENPWmO fQADBBcHsexVV8/CjCkzfYiXPC7dMAT7OZE+nXSZJHQiCR0LUSToICFZ+Pntj1bjMLu9mDSy AtnheBEXom1b7TTHOZ13HuU4Cue9iNoACjVbbF9Zg4+YRmvtcPy8tTo5DXBdysrF7sO/yWGu ukgWa2otyae8BC7qBYFbm6uk9wMbYSN3yYBmbiAULMrBKA33iWlE0rIKMv91a2DVjp4NiOSu gyyFD9n83Sn4lcyjdLvBUCn9zgY4TwufG/ozyF2hSmO3iIzqt0GxmpQ+pBXk/m51D/UoTWGl deE0Dvw98SWmZSNtdOPnJZ0D Message-ID: Date: Tue, 15 Oct 2019 15:06:41 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191015_150647_314932_9D53336C X-CRM114-Status: GOOD ( 13.35 ) X-BeenThere: linux-snps-arc@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on Synopsys ARC Processors List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch , Arnd Bergmann , Peter Zijlstra , "Aneesh Kumar K . V" , Linux Kernel Mailing List , Nick Piggin , Linux-MM , Andrew Morton , linux-snps-arc@lists.infradead.org, Will Deacon , "Kirill A . Shutemov" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+linux-snps-arc=archiver.kernel.org@lists.infradead.org On 10/15/19 2:48 PM, Linus Torvalds wrote: > On Tue, Oct 15, 2019 at 12:19 PM Vineet Gupta > wrote: >> This is a non-functional change anyways since ARC has software page walker >> with 2 lookup levels (pgd -> pte) > > Could we encourage other architectures to do the same, and get rid of > all uses of __ARCH_USE_5LEVEL_HACK? IMHO this should have been done at the onset. The actual changes don't seem that difficult, just need to add the missing p4d calls although I can sympathize with hassles of coordinating/building/testing/yadi yada cross arch. OTOH, the [45]LEVEL_HACK seem like a nice way to "fold" the levels: the skipped/folded level vanishes completely. Among others it does things like #define p4d_t pgd_t On ARC 2-level code: free_pte_range pmd_pgtable(*pmd); ((((((*pmd).pud).pgd))) & PAGE_MASK)); <-- 5LEVEL_HACK vs. ((((((((*pmd).pud).p4d).pgd)))) & PAGE_MASK )); <-- w/o 5LEVEL_HACK pmd_clear(pmd); *(pmd)).pud).pgd)))) = 0 vs. *(pmd)).pud).p4d).pgd)))) = 0 So we may not be able to fix all he historical misgivigs, but this might alleviate the pain a bit. I'll try to dabble a bit. Thx for taking a look and te ACKs. -Vineet _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc