linux-kernel - Re: [PATCH 1/3] riscv: Fix memory_limit for 64-bit kernel

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Message-ID: <8e1bef59-8a65-dfdf-d09d-f578323348be@ghiti.fr>
Date:   Thu, 1 Jul 2021 21:01:10 +0200
From:   Alex Ghiti <alex@...ti.fr>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] riscv: Fix memory_limit for 64-bit kernel

Le 1/07/2021 à 12:44, Kefeng Wang a écrit :
> 
> On 2021/6/29 17:13, Alexandre Ghiti wrote:
>> As described in Documentation/riscv/vm-layout.rst, the end of the
>> virtual address space for 64-bit kernel is occupied by the modules/BPF/
>> kernel mappings so this actually reduces the amount of memory we are able
>> to map and then use in the linear mapping. So make sure this limit is
>> correctly set.
>>
>> Fixes: c9811e379b21 ("riscv: Add mem kernel parameter support")
> 
> 
> Should the Fixes tag be de043da0b9e7 （“RISC-V: Fix usage of 
> memblock_enforce_memory_limit“）,
> 
> The -PAGE_OFFSET is set to the maximal physical memory from this point :)

Oops, thank you!

Alex

> 
>> Signed-off-by: Alexandre Ghiti <alex@...ti.fr>
>> ---
>>   arch/riscv/mm/init.c | 11 +++++++++--
>>   1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>> index 12f956b3a674..04a5db3a9788 100644
>> --- a/arch/riscv/mm/init.c
>> +++ b/arch/riscv/mm/init.c
>> @@ -124,10 +124,17 @@ void __init mem_init(void)
>>   }
>>   /*
>> - * The default maximal physical memory size is -PAGE_OFFSET,
>> - * limit the memory size via mem.
>> + * The default maximal physical memory size is -PAGE_OFFSET for 
>> 32-bit kernel,
>> + * whereas for 64-bit kernel, the end of the virtual address space is 
>> occupied
>> + * by the modules/BPF/kernel mappings which reduces the available 
>> size of the
>> + * linear mapping.
>> + * Limit the memory size via mem.
>>    */
>> +#ifdef CONFIG_64BIT
>> +static phys_addr_t memory_limit = -PAGE_OFFSET - SZ_4G;
>> +#else
>>   static phys_addr_t memory_limit = -PAGE_OFFSET;
>> +#endif
>>   static int __init early_mem(char *p)
>>   {
> 
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