linux-kernel - Re: [PATCH 02/14] MIPS: memblock: Surely map BSS kernel memory section

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Date:   Tue, 23 Jan 2018 00:47:46 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Matt Redfearn <matt.redfearn@...s.com>
Cc:     ralf@...ux-mips.org, miodrag.dinic@...s.com, jhogan@...nel.org,
        goran.ferenc@...s.com, david.daney@...ium.com,
        paul.gortmaker@...driver.com, paul.burton@...s.com,
        alex.belits@...ium.com, Steven.Hill@...ium.com,
        alexander.sverdlin@...ia.com, kumba@...too.org,
        marcin.nowakowski@...s.com, James.hogan@...s.com,
        Peter.Wotton@...s.com, Sergey.Semin@...latforms.ru,
        linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/14] MIPS: memblock: Surely map BSS kernel memory
 section

Hello Matt,

On Mon, Jan 22, 2018 at 04:35:26PM +0000, Matt Redfearn <matt.redfearn@...s.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
memory now I'd also merged them into a single call for the range [_text, _end].
What do you think?

Regards,
-Sergey

> 
> Reviewed-by: Matt Redfearn <matt.redfearn@...s.com>
> 
> Thanks,
> Matt
> 
> >
> >Signed-off-by: Serge Semin <fancer.lancer@...il.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();
> >