On Wed, Oct 24, 2018 at 3:01 PM Florian Fainelli <f.fainelli@xxxxxxxxx> wrote: > > On 10/24/18 12:55 PM, Rob Herring wrote: > > On Wed, Oct 24, 2018 at 2:33 PM Florian Fainelli <f.fainelli@xxxxxxxxx> 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. :) > > > > This one was by far the most invasive one due to its include chain, but > yes, there would be many more that could be optimized. > > >> 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. > > OK, let me cook a patch doing that and meanwhile I will look at how much > work is involved to implement the above option you outlined, which also > sounds entirely reasonable. BTW, I would suspect that initrd_below_start_ok being 1 is not okay for most arches. I'm not sure how that would work. min_low_pfn is typically based on the start of memory. arm64 is not even setting it. Rob > -- > Florian
