Hello Matt, On Wed, Jan 24, 2018 at 09:49:31AM +0000, Matt Redfearn <matt.redfearn@xxxxxxxx> wrote: > Hi Serge, > > On 23/01/18 19:27, Serge Semin wrote: > >Hello Matt, > > > >On Tue, Jan 23, 2018 at 11:03:27AM +0000, Matt Redfearn <matt.redfearn@xxxxxxxx> wrote: > >>Hi Serge, > >> > >>On 22/01/18 21:47, Serge Semin wrote: > >>>Hello Matt, > >>> > >>>On Mon, Jan 22, 2018 at 04:35:26PM +0000, Matt Redfearn <matt.redfearn@xxxxxxxx> wrote: > >>>>Hi Serge, > >>>> > >>>>On 17/01/18 22:23, Serge Semin wrote: > >>>>>The current MIPS code makes sure the kernel code/data/init > >>>>>sections are in the maps, but BSS should also be there. > >>>> > >>>>Quite right - it should. But this was protected against by reserving all > >>>>bootmem up to the _end symbol here: > >>>>http://elixir.free-electrons.com/linux/v4.15-rc8/source/arch/mips/kernel/setup.c#L388 > >>>>Which you remove in the next patch in this series. I'm not sure it is worth > >>> > >>>Right. Missed that part. The old code just doesn't set the kernel memory free > >>>calling the free_bootmem() method for non-reserved parts below reserved_end. > >>> > >>>>disentangling the reserved_end stuff from the next patch to make this into a > >>>>single logical change of reserving just .bss rather than everything below > >>>>_end. > >>> > >>>Good point. I'll move this change into the "[PATCH 05/14] MIPS: memblock: > >>>Add reserved memory regions to memblock". It logically belongs to that place. > >>>Since basically by the arch_mem_addpart() calls we reserve all the kernel > >> > >> > >>Actually I was wrong - it's not this sequence of arch_mem_addpart's that > >>reserves the kernels memory. At least on DT based systems, it's pretty > >>likely that these regions will overlap with the system memory already added. > >>of_scan_flat_dt will look for the memory node and add it via > >>early_init_dt_add_memory_arch. > >>These calls to add the kernel text, init and bss detect that they overlap > >>with the already present system memory, so don't get added, here: > >>http://elixir.free-electrons.com/linux/v4.15-rc9/source/arch/mips/kernel/setup.c#L759 > >> > >>As such, when we print out the content of boot_mem_map, we only have a > >>single entry: > >> > >>[ 0.000000] Determined physical RAM map: > >>[ 0.000000] memory: 10000000 @ 00000000 (usable) > >> > >> > >>>memory now I'd also merged them into a single call for the range [_text, _end]. > >>>What do you think? > >> > >> > >>I think that this patch makes sense in case the .bss is for some reason not > >>covered by an existing entry, but I would leave it as a separate patch. > >> > >>Your [PATCH 05/14] MIPS: memblock: Add reserved memory regions to memblock > >>is actually self-contained since it replaces reserving all memory up to _end > >>with the single reservation of the kernel's whole size > >> > >>+ size = __pa_symbol(&_end) - __pa_symbol(&_text); > >>+ memblock_reserve(__pa_symbol(&_text), size); > >> > >> > >>Which I think is definitely an improvement since it is much clearer. > >> > > > >Alright lets sum it up. First of all, yeah, you are right, arch_mem_addpart() > >is created to make sure the kernel memory is added to the memblock/bootmem pool. > >The previous arch code was leaving such the memory range non-freed since it was > >higher the reserved_end, so to make sure the early memory allocations wouldn't > >be made from the pages, where kernel actually resides. > > > >In my code I still wanted to make sure the kernel memory is in the memblock pool. > >But I also noticed, that .bss memory range wouldn't be added to the pool if neither > >dts nor platform-specific code added any memory to the boot_mem_map pool. So I > >decided to fix it. The actual kernel memory reservation is performed after all > >the memory regions are declared by the code you cited. It's essential to do > >the [_text, _end] memory range reservation there, otherwise memblock may > >allocate from the memory range occupied by the kernel code/data. > > > >Since you agree with leaving it in the separate patch, I'd only suggest to > >call the arch_mem_addpart() method for just one range [_text, _end] instead of > >doing it three times for a separate _text, _data and bss sections. What do you > >think? > > I think it's best left as 3 separate reservations, mainly due to the > different attribute used for the init section. So all in all, I like this > patch as it is. > Alright. I'll leave as is. Lets see what others think about it. Regards, -Sergey > Thanks, > Matt > > > > >Regards, > >-Sergey > > > >>Thanks, > >>Matt > >> > >>> > >>>Regards, > >>>-Sergey > >>> > >>>> > >>>>Reviewed-by: Matt Redfearn <matt.redfearn@xxxxxxxx> > >>>> > >>>>Thanks, > >>>>Matt > >>>> > >>>>> > >>>>>Signed-off-by: Serge Semin <fancer.lancer@xxxxxxxxx> > >>>>>--- > >>>>> arch/mips/kernel/setup.c | 3 +++ > >>>>> 1 file changed, 3 insertions(+) > >>>>> > >>>>>diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c > >>>>>index 76e9e2075..0d21c9e04 100644 > >>>>>--- a/arch/mips/kernel/setup.c > >>>>>+++ b/arch/mips/kernel/setup.c > >>>>>@@ -845,6 +845,9 @@ static void __init arch_mem_init(char **cmdline_p) > >>>>> arch_mem_addpart(PFN_UP(__pa_symbol(&__init_begin)) << PAGE_SHIFT, > >>>>> PFN_DOWN(__pa_symbol(&__init_end)) << PAGE_SHIFT, > >>>>> BOOT_MEM_INIT_RAM); > >>>>>+ arch_mem_addpart(PFN_DOWN(__pa_symbol(&__bss_start)) << PAGE_SHIFT, > >>>>>+ PFN_UP(__pa_symbol(&__bss_stop)) << PAGE_SHIFT, > >>>>>+ BOOT_MEM_RAM); > >>>>> pr_info("Determined physical RAM map:\n"); > >>>>> print_memory_map(); > >>>>>
