From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH v2 0/2] arm64: Cut rebuild time when changing CONFIG_BLK_DEV_INITRD Date: Thu, 25 Oct 2018 10:51:34 +0100 Message-ID: <20181025095134.GX30658@n2100.armlinux.org.uk> References: <20181024193256.23734-1-f.fainelli@gmail.com> <20181025093833.GA23607@rapoport-lnx> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Rob Herring , Linux-MIPS , linux-ia64@vger.kernel.org, SH-Linux , Catalin Marinas , Will Deacon , devicetree@vger.kernel.org, sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, "open list:GENERIC INCLUDE/ASM HEADER FILES" , linux-s390@vger.kernel.org, Florian Fainelli , linux-c6x-dev@linux-c6x.org, linux-hexagon@vger.kernel.org, arcml , "moderated list:H8/300 ARCHITECTURE" , linux-xtensa@linux-xtensa.org, Arnd Bergmann , Marc Zyngier , linux-um@lists.infradead.org, linux-m68k@lists To: Mike Rapoport Return-path: In-Reply-To: <20181025093833.GA23607@rapoport-lnx> List-ID: List-Id: linux-parisc.vger.kernel.org On Thu, Oct 25, 2018 at 10:38:34AM +0100, Mike Rapoport wrote: > On Wed, Oct 24, 2018 at 02:55:17PM -0500, Rob Herring wrote: > > On Wed, Oct 24, 2018 at 2:33 PM Florian Fainelli wrote: > > > > > > Hi all, > > > > > > While investigating why ARM64 required a ton of objects to be rebuilt > > > when toggling CONFIG_DEV_BLK_INITRD, it became clear that this was > > > because we define __early_init_dt_declare_initrd() differently and we do > > > that in arch/arm64/include/asm/memory.h which gets included by a fair > > > amount of other header files, and translation units as well. > > > > I scratch my head sometimes as to why some config options rebuild so > > much stuff. One down, ? to go. :) > > > > > Changing the value of CONFIG_DEV_BLK_INITRD is a common thing with build > > > systems that generate two kernels: one with the initramfs and one > > > without. buildroot is one of these build systems, OpenWrt is also > > > another one that does this. > > > > > > This patch series proposes adding an empty initrd.h to satisfy the need > > > for drivers/of/fdt.c to unconditionally include that file, and moves the > > > custom __early_init_dt_declare_initrd() definition away from > > > asm/memory.h > > > > > > This cuts the number of objects rebuilds from 1920 down to 26, so a > > > factor 73 approximately. > > > > > > Apologies for the long CC list, please let me know how you would go > > > about merging that and if another approach would be preferable, e.g: > > > introducing a CONFIG_ARCH_INITRD_BELOW_START_OK Kconfig option or > > > something like that. > > > > There may be a better way as of 4.20 because bootmem is now gone and > > only memblock is used. This should unify what each arch needs to do > > with initrd early. We need the physical address early for memblock > > reserving. Then later on we need the virtual address to access the > > initrd. Perhaps we should just change initrd_start and initrd_end to > > physical addresses (or add 2 new variables would be less invasive and > > allow for different translation than __va()). The sanity checks and > > memblock reserve could also perhaps be moved to a common location. > > > > Alternatively, given arm64 is the only oddball, I'd be fine with an > > "if (IS_ENABLED(CONFIG_ARM64))" condition in the default > > __early_init_dt_declare_initrd as long as we have a path to removing > > it like the above option. > > I think arm64 does not have to redefine __early_init_dt_declare_initrd(). > Something like this might be just all we need (completely untested, > probably it won't even compile): The alternative solution would be to replace initrd_start/initrd_end with physical address versions of these everywhere - that's what we're passed from DT, it's what 32-bit ARM would prefer, and seemingly what 64-bit ARM would also like as well. Grepping for initrd_start in arch/*/mm shows that there's lots of architectures that have virtual/physical conversions on these, and a number that have obviously been derived from 32-bit ARM's approach (with maintaining a phys_initrd_start variable to simplify things). -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up