linux-kernel - Re: [PATCH v2] MIPS: fix incorrect mem=X@Y handling

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Message-ID: <CA+7wUszKJbZTs-8W6s-4a-N7MB=7OrV3Uyp0v-ZZiHmRTVNazw@mail.gmail.com>
Date:   Wed, 31 Jan 2018 08:47:35 +0100
From:   Mathieu Malaterre <malat@...ian.org>
To:     Marcin Nowakowski <marcin.nowakowski@...s.com>
Cc:     "# v4 . 11" <stable@...r.kernel.org>,
        James Hogan <jhogan@...nel.org>,
        Ralf Baechle <ralf@...ux-mips.org>, linux-mips@...ux-mips.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] MIPS: fix incorrect mem=X@Y handling

Hi Marcin,

Since it's been a week, could you confirm the patch is ok as-is or do
you think some comment(s) from James should be incorporated ?

On Tue, Jan 23, 2018 at 3:17 PM, James Hogan <jhogan@...nel.org> wrote:
> On Thu, Dec 21, 2017 at 10:00:59PM +0100, Mathieu Malaterre wrote:
>> From: Marcin Nowakowski <marcin.nowakowski@...s.com>
>>
>> Change 73fbc1eba7ff added a fix to ensure that the memory range between
>
> Please refer to commits with e.g. commit 73fbc1eba7ff ("MIPS: fix
> mem=X@Y commandline processing").
>
>> PHYS_OFFSET and low memory address specified by mem= cmdline argument is
>> not later processed by free_all_bootmem.
>> This change was incorrect for systems where the commandline specifies
>> more than 1 mem argument, as it will cause all memory between
>> PHYS_OFFSET and each of the memory offsets to be marked as reserved,
>> which results in parts of the RAM marked as reserved (Creator CI20's
>> u-boot has a default commandline argument 'mem=256M@0x0
>> mem=768M@...0000000').
>>
>> Change the behaviour to ensure that only the range between PHYS_OFFSET
>> and the lowest start address of the memories is marked as protected.
>>
>> This change also ensures that the range is marked protected even if it's
>> only defined through the devicetree and not only via commandline
>> arguments.
>>
>> Reported-by: Mathieu Malaterre <mathieu.malaterre@...il.com>
>> Signed-off-by: Marcin Nowakowski <marcin.nowakowski@...s.com>
>> Fixes: 73fbc1eba7ff ("MIPS: fix mem=X@Y commandline processing")
>> Cc: <stable@...r.kernel.org> # v4.11
>
> I'm guessing that should technically be v4.11+

My fault, if this is the only change, I can re-submit.

>> ---
>> v2: Use updated email adress, add tag for stable.
>>  arch/mips/kernel/setup.c | 19 ++++++++++++++++---
>>  1 file changed, 16 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
>> index 702c678de116..f19d61224c71 100644
>> --- a/arch/mips/kernel/setup.c
>> +++ b/arch/mips/kernel/setup.c
>> @@ -375,6 +375,7 @@ static void __init bootmem_init(void)
>>       unsigned long reserved_end;
>>       unsigned long mapstart = ~0UL;
>>       unsigned long bootmap_size;
>> +     phys_addr_t ramstart = ~0UL;
>
> Although practically it might not matter, technically phys_addr_t may be
> 64-bits (CONFIG_PHYS_ADDR_T_64BIT) even on a 32-bit kernels, in which
> case ~0UL may not be sufficiently large.
>
> Maybe that should be ~(phys_addr_t)0, or perhaps (phys_addr_t)ULLONG_MAX
> to match add_memory_region().
>
>>       bool bootmap_valid = false;
>>       int i;
>>
>> @@ -395,6 +396,21 @@ static void __init bootmem_init(void)
>>       max_low_pfn = 0;
>>
>>       /*
>> +      * Reserve any memory between the start of RAM and PHYS_OFFSET
>> +      */
>> +     for (i = 0; i < boot_mem_map.nr_map; i++) {
>> +             if (boot_mem_map.map[i].type != BOOT_MEM_RAM)
>> +                     continue;
>> +
>> +             ramstart = min(ramstart, boot_mem_map.map[i].addr);
>
> Is it worth incorporating this into the existing loop below ...
>
>> +     }
>> +
>> +     if (ramstart > PHYS_OFFSET)
>> +             add_memory_region(PHYS_OFFSET, ramstart - PHYS_OFFSET,
>> +                               BOOT_MEM_RESERVED);
>
> ... and this then placed below that loop?
>
> Otherwise I can't find fault with this patch, though i'm not intimately
> familiar with bootmem.
>
> Cheers
> James
>
>> +
>> +
>> +     /*
>>        * Find the highest page frame number we have available.
>>        */
>>       for (i = 0; i < boot_mem_map.nr_map; i++) {
>> @@ -664,9 +680,6 @@ static int __init early_parse_mem(char *p)
>>
>>       add_memory_region(start, size, BOOT_MEM_RAM);
>>
>> -     if (start && start > PHYS_OFFSET)
>> -             add_memory_region(PHYS_OFFSET, start - PHYS_OFFSET,
>> -                             BOOT_MEM_RESERVED);
>>       return 0;
>>  }
>>  early_param("mem", early_parse_mem);
>> --
>> 2.11.0
>>