From: Serge Semin <fancer.lancer@gmail.com>
To: Matt Redfearn <matt.redfearn@mips.com>
Cc: ralf@linux-mips.org, miodrag.dinic@mips.com, jhogan@kernel.org,
goran.ferenc@mips.com, david.daney@cavium.com,
paul.gortmaker@windriver.com, paul.burton@mips.com,
alex.belits@cavium.com, Steven.Hill@cavium.com,
alexander.sverdlin@nokia.com, kumba@gentoo.org,
marcin.nowakowski@mips.com, James.hogan@mips.com,
Peter.Wotton@mips.com, Sergey.Semin@t-platforms.ru,
linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 02/14] MIPS: memblock: Surely map BSS kernel memory section
Date: Tue, 23 Jan 2018 22:27:07 +0300 [thread overview]
Message-ID: <20180123192707.GB28147@mobilestation> (raw)
In-Reply-To: <8a26c7cd-966f-90d4-96c9-2f974808c2f4@mips.com>
Hello Matt,
On Tue, Jan 23, 2018 at 11:03:27AM +0000, Matt Redfearn <matt.redfearn@mips.com> 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@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.
>
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?
Regards,
-Sergey
> 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();
> >>>
next prev parent reply other threads:[~2018-01-23 19:26 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-17 22:22 [PATCH 00/14] MIPS: memblock: Switch arch code to NO_BOOTMEM Serge Semin
2018-01-17 22:22 ` [PATCH 01/14] MIPS: memblock: Add RESERVED_NOMAP memory flag Serge Semin
2018-01-17 22:23 ` [PATCH 02/14] MIPS: memblock: Surely map BSS kernel memory section Serge Semin
2018-01-22 16:35 ` Matt Redfearn
2018-01-22 21:47 ` Serge Semin
2018-01-23 11:03 ` Matt Redfearn
2018-01-23 19:27 ` Serge Semin [this message]
2018-01-24 9:49 ` Matt Redfearn
2018-01-24 10:03 ` Serge Semin
2018-01-17 22:23 ` [PATCH 03/14] MIPS: memblock: Reserve initrd memory in memblock Serge Semin
2018-01-17 22:23 ` [PATCH 04/14] MIPS: memblock: Discard bootmem initialization Serge Semin
2018-01-17 22:23 ` [PATCH 05/14] MIPS: memblock: Add reserved memory regions to memblock Serge Semin
2018-01-17 22:23 ` [PATCH 06/14] MIPS: memblock: Reserve kdump/crash regions in memblock Serge Semin
2018-01-17 22:23 ` [PATCH 07/14] MIPS: memblock: Mark present sparsemem sections Serge Semin
2018-01-24 6:13 ` Marcin Nowakowski
2018-01-24 7:27 ` Serge Semin
2018-01-17 22:23 ` [PATCH 08/14] MIPS: memblock: Simplify DMA contiguous reservation Serge Semin
2018-01-17 22:23 ` [PATCH 09/14] MIPS: memblock: Allow memblock regions resize Serge Semin
2018-01-17 22:23 ` [PATCH 10/14] MIPS: memblock: Perform early low memory test Serge Semin
2018-01-17 22:23 ` [PATCH 11/14] MIPS: memblock: Print out kernel virtual mem layout Serge Semin
2018-01-18 20:03 ` Florian Fainelli
2018-01-18 20:18 ` Serge Semin
2018-01-19 7:59 ` Matt Redfearn
2018-01-19 14:27 ` Serge Semin
2018-01-23 15:35 ` Matt Redfearn
2018-01-23 19:10 ` Serge Semin
2018-01-24 9:46 ` Matt Redfearn
2018-01-24 10:08 ` Serge Semin
2018-01-17 22:23 ` [PATCH 12/14] MIPS: memblock: Discard bootmem from Loongson3 code Serge Semin
2018-01-23 22:28 ` Jiaxun Yang
2018-01-23 19:36 ` Serge Semin
2018-01-17 22:23 ` [PATCH 13/14] MIPS: memblock: Discard bootmem from SGI IP27 code Serge Semin
2018-01-17 22:23 ` [PATCH 14/14] MIPS: memblock: Deactivate bootmem allocator Serge Semin
2018-01-23 23:59 ` James Hogan
2018-01-24 8:28 ` Serge Semin
2018-01-22 16:36 ` [PATCH 00/14] MIPS: memblock: Switch arch code to NO_BOOTMEM Matt Redfearn
2018-01-22 21:33 ` Serge Semin
2018-01-23 11:29 ` Mathieu Malaterre
2018-01-23 14:01 ` Matt Redfearn
2018-01-25 17:58 ` Alexander Sverdlin
2018-01-25 20:17 ` Serge Semin
2018-01-31 0:21 ` Serge Semin
2018-02-02 3:54 ` [PATCH v2 00/15] " Serge Semin
2018-02-02 3:54 ` [PATCH v2 01/15] MIPS: memblock: Add RESERVED_NOMAP memory flag Serge Semin
2018-02-13 11:21 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 02/15] MIPS: memblock: Surely map BSS kernel memory section Serge Semin
2018-02-13 11:22 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 03/15] MIPS: memblock: Reserve initrd memory in memblock Serge Semin
2018-02-13 11:22 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 04/15] MIPS: memblock: Discard bootmem initialization Serge Semin
2018-02-13 11:28 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 05/15] MIPS: KASLR: Drop relocatable fixup from reservation_init Serge Semin
2018-02-13 11:30 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 06/15] MIPS: memblock: Add reserved memory regions to memblock Serge Semin
2018-02-13 13:44 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 07/15] MIPS: memblock: Reserve kdump/crash regions in memblock Serge Semin
2018-02-13 13:45 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 08/15] MIPS: memblock: Mark present sparsemem sections Serge Semin
2018-02-13 13:50 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 09/15] MIPS: memblock: Simplify DMA contiguous reservation Serge Semin
2018-02-13 13:51 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 10/15] MIPS: memblock: Allow memblock regions resize Serge Semin
2018-02-13 13:55 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 11/15] MIPS: memblock: Perform early low memory test Serge Semin
2018-02-13 14:01 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 12/15] MIPS: memblock: Print out kernel virtual mem layout Serge Semin
2018-02-13 14:05 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 13/15] MIPS: memblock: Discard bootmem from Loongson3 code Serge Semin
2018-02-13 14:09 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 14/15] MIPS: memblock: Discard bootmem from SGI IP27 code Serge Semin
2018-02-13 14:17 ` Matt Redfearn
2018-02-02 3:54 ` [PATCH v2 15/15] MIPS: memblock: Deactivate bootmem allocator Serge Semin
2018-02-13 14:18 ` Matt Redfearn
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