Messages in this thread Patch in this message | | | Subject | Re: [PATCH 02/14] MIPS: memblock: Surely map BSS kernel memory section | From | Matt Redfearn <> | Date | Tue, 23 Jan 2018 11:03:27 +0000 |
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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@mips.com> 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.
Thanks, Matt
> > Regards, > -Sergey > >> >> Reviewed-by: Matt Redfearn <matt.redfearn@mips.com> >> >> Thanks, >> Matt >> >>> >>> Signed-off-by: Serge Semin <fancer.lancer@gmail.com> >>> --- >>> 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(); >>>
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