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Tue, 14 Apr 2020 04:41:35 -0700 (PDT) Received: from localhost ([203.18.28.220]) by smtp.gmail.com with ESMTPSA id 132sm11155833pfc.183.2020.04.14.04.41.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2020 04:41:35 -0700 (PDT) Date: Tue, 14 Apr 2020 21:39:53 +1000 From: Nicholas Piggin Subject: Re: [PATCH v2 4/4] mm/vmalloc: Hugepage vmalloc mappings To: Matthew Wilcox References: <20200413125303.423864-1-npiggin@gmail.com> <20200413125303.423864-5-npiggin@gmail.com> <20200413134106.GN21484@bombadil.infradead.org> In-Reply-To: <20200413134106.GN21484@bombadil.infradead.org> MIME-Version: 1.0 Message-Id: <1586863931.xb4yeowkao.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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: linux-arch@vger.kernel.org, Will Deacon , Catalin Marinas , x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Thomas Gleixner , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Excerpts from Matthew Wilcox's message of April 13, 2020 11:41 pm: > On Mon, Apr 13, 2020 at 10:53:03PM +1000, Nicholas Piggin wrote: >> +static int vmap_pages_range_noflush(unsigned long start, unsigned long = end, >> + pgprot_t prot, struct page **pages, >> + unsigned int page_shift) >> +{ >> + if (page_shift =3D=3D PAGE_SIZE) { >=20 > ... I think you meant 'page_shift =3D=3D PAGE_SHIFT' Thanks, good catch. I obviously didn't test the fallback path (the other path works for small pages, it just goes one at a time). > Overall I like this series, although it's a bit biased towards CPUs > which have page sizes which match PMD/PUD sizes. It doesn't offer the > possibility of using 64kB page sizes on ARM, for example. No, it's just an incremental step on existing huge vmap stuff in tree, so such a thing would be out of scope. > But it's a > step in the right direction. >=20 I don't know about moving kernel maps away from a generic Linux page table format. I quite like moving to it and making it as generic as possible. On the other hand, I also would like to make some arch-specific allowances for certain special cases that may not fit within the standard page table format, but it might be a much more specific and limited interface than the general vmalloc stuff. Thanks, Nick