Re: [PATCH] powerpc: align memory_limit to 16MB in early_parse_mem

[Christophe Leroy]

Le 10/04/2024 à 17:22, Joel Savitz a écrit :
> [Vous ne recevez pas souvent de courriers de jsavitz@xxxxxxxxxx. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
> 
> On Mon, Apr 1, 2024 at 10:17 AM Joel Savitz <jsavitz@xxxxxxxxxx> wrote:
>>
>> On Tue, Mar 26, 2024 at 12:45 AM Joel Savitz <jsavitz@xxxxxxxxxx> wrote:
>>>
>>> On Fri, Mar 8, 2024 at 5:18 AM Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxx> wrote:
>>>>
>>>> Joel Savitz <jsavitz@xxxxxxxxxx> writes:
>>>>
>>>>> On 64-bit powerpc, usage of a non-16MB-aligned value for the mem= kernel
>>>>> cmdline parameter results in a system hang at boot.
>>>>>
>>>>> For example, using 'mem=4198400K' will always reproduce this issue.
>>>>>
>>>>> This patch fixes the problem by aligning any argument to mem= to 16MB
>>>>> corresponding with the large page size on powerpc.
>>>>>
>>>>> Fixes: 2babf5c2ec2f ("[PATCH] powerpc: Unify mem= handling")
>>>>> Co-developed-by: Gonzalo Siero <gsierohu@xxxxxxxxxx>
>>>>> Signed-off-by: Gonzalo Siero <gsierohu@xxxxxxxxxx>
>>>>> Signed-off-by: Joel Savitz <jsavitz@xxxxxxxxxx>
>>>>> ---
>>>>>   arch/powerpc/kernel/prom.c | 6 +++++-
>>>>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
>>>>> index 0b5878c3125b..8cd3e2445d8a 100644
>>>>> --- a/arch/powerpc/kernel/prom.c
>>>>> +++ b/arch/powerpc/kernel/prom.c
>>>>> @@ -82,8 +82,12 @@ static int __init early_parse_mem(char *p)
>>>>>   {
>>>>>        if (!p)
>>>>>                return 1;
>>>>> -
>>>>> +#ifdef CONFIG_PPC64
>>>>> +     /* Align to 16 MB == size of ppc64 large page */
>>>>> +     memory_limit = ALIGN(memparse(p, &p), 0x1000000);
>>>>> +#else
>>>>>        memory_limit = PAGE_ALIGN(memparse(p, &p));
>>>>> +#endif
>>>>>        DBG("memory limit = 0x%llx\n", memory_limit);
>>>>>
>>>>>        return 0;
>>>>> --
>>>>> 2.43.0
>>>>
>>>> Can you try this change?
>>>>
>>>> commit 5555bc55e1aa71f545cff31e1eccdb4a2e39df84
>>>> Author: Aneesh Kumar K.V (IBM) <aneesh.kumar@xxxxxxxxxx>
>>>> Date:   Fri Mar 8 14:45:26 2024 +0530
>>>>
>>>>      powerpc/mm: Align memory_limit value specified using mem= kernel parameter
>>>>
>>>>      The value specified for the memory limit is used to set a restriction on
>>>>      memory usage. It is important to ensure that this restriction is within
>>>>      the linear map kernel address space range. The hash page table
>>>>      translation uses a 16MB page size to map the kernel linear map address
>>>>      space. htab_bolt_mapping() function aligns down the size of the range
>>>>      while mapping kernel linear address space. Since the memblock limit is
>>>>      enforced very early during boot, before we can detect the type of memory
>>>>      translation (radix vs hash), we align the memory limit value specified
>>>>      as a kernel parameter to 16MB. This alignment value will work for both
>>>>      hash and radix translations.
>>>>
>>>>      Signed-off-by: Aneesh Kumar K.V (IBM) <aneesh.kumar@xxxxxxxxxx>
>>>>
>>>> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
>>>> index 0b5878c3125b..9bd965d35352 100644
>>>> --- a/arch/powerpc/kernel/prom.c
>>>> +++ b/arch/powerpc/kernel/prom.c
>>>> @@ -824,8 +824,11 @@ void __init early_init_devtree(void *params)
>>>>                  reserve_crashkernel();
>>>>          early_reserve_mem();
>>>>
>>>> -       /* Ensure that total memory size is page-aligned. */
>>>> -       limit = ALIGN(memory_limit ?: memblock_phys_mem_size(), PAGE_SIZE);
>>>> +       if (memory_limit > memblock_phys_mem_size())
>>>> +               memory_limit = 0;
>>>> +
>>>> +       /* Align down to 16 MB which is large page size with hash page translation */
>>>> +       limit = ALIGN_DOWN(memory_limit ?: memblock_phys_mem_size(), SZ_16M);
>>>>          memblock_enforce_memory_limit(limit);
>>>>
>>>>   #if defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_PPC_4K_PAGES)
>>>> diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
>>>> index e67effdba85c..d6410549e141 100644
>>>> --- a/arch/powerpc/kernel/prom_init.c
>>>> +++ b/arch/powerpc/kernel/prom_init.c
>>>> @@ -817,8 +817,8 @@ static void __init early_cmdline_parse(void)
>>>>                  opt += 4;
>>>>                  prom_memory_limit = prom_memparse(opt, (const char **)&opt);
>>>>   #ifdef CONFIG_PPC64
>>>> -               /* Align to 16 MB == size of ppc64 large page */
>>>> -               prom_memory_limit = ALIGN(prom_memory_limit, 0x1000000);
>>>> +               /* Align down to 16 MB which is large page size with hash page translation */
>>>> +               prom_memory_limit = ALIGN_DOWN(prom_memory_limit, SZ_16M);
>>>>   #endif
>>>>          }
>>>>
>>>>
>>>
>>> Sorry for the delayed reply. I just tested this patch and it fixes the
>>> bug for me.
>>
>> Hi,
>>
>> Just a quick follow up on this.
>>
>> The above patch fixed the bug for me.
>>
>> How do we want to proceed?
>>
>> Best,
>> Joel Savitz
> 
> Hi,
> 
> I haven't heard anything on this thread so I'm just sending a quick follow up.
> 
> Do we want to merge this
> 

Is it the same as 
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20240403083611.172833-1-aneesh.kumar@xxxxxxxxxx/ 
?