Re: [PATCH 1/2] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 2022/3/30 6:29, Vijay Balakrishna wrote:
>
>
> On 3/24/2022 10:53 PM, Kefeng Wang wrote:
>> The kernel could be benifit due to BLOCK_MAPPINGS, see commit
>> 031495635b46 ("arm64: Do not defer reserve_crashkernel() for
>> platforms with no DMA memory zones"), if there is only with
>> ZONE_DMA32, we could set arm64_dma_phys_limit to max_zone_phys(32)
>> earlier in arm64_memblock_init(), then we will benifit too.
>
> Thanks for noticing platforms with just ZONE_DMA32 config can also 
> benefit BLOCK_MAPPINGS.  I assume you have access to one where you 
> notice the difference with proposed changes and able to test.  I did 
> test proposed changes on SoC we use with IOMMU (no ZONE_DMA configs 
> enabled).
I backported your patches into 5.10 and tested(unixbench will benifit 
due to block mapping, only with DMA32 and rodata=false)
>
> Nits --
> - benifit -> benefit
> - consider making commit message clear, "then we will.." seems you are 
> referring to platforms with just ZONE_DMA32 config enabled
> - to reflect new change consider updating comment added in commit 
> 031495635b46
Thanks for your reviewing,  will update and test with upstream.
>
>>
>> Cc: Vijay Balakrishna <vijayb@linux.microsoft.com>
>> Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
>> Cc: Will Deacon <will@kernel.org>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>
> Reviewed-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
>
>> ---
>>   arch/arm64/mm/init.c | 18 ++++++++++--------
>>   arch/arm64/mm/mmu.c  |  6 ++----
>>   2 files changed, 12 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>> index 8ac25f19084e..9dded8779d72 100644
>> --- a/arch/arm64/mm/init.c
>> +++ b/arch/arm64/mm/init.c
>> @@ -157,14 +157,14 @@ static phys_addr_t __init 
>> max_zone_phys(unsigned int zone_bits)
>>       return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
>>   }
>>   +phys_addr_t __ro_after_init dma32_phys_limit;
Will make it static, suggested by Florian
>>   static void __init zone_sizes_init(unsigned long min, unsigned long 
>> max)
>>   {
>>       unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
>> -    unsigned int __maybe_unused acpi_zone_dma_bits;
>> -    unsigned int __maybe_unused dt_zone_dma_bits;
>> -    phys_addr_t __maybe_unused dma32_phys_limit = max_zone_phys(32);
>> -
>>   #ifdef CONFIG_ZONE_DMA
>> +    unsigned int acpi_zone_dma_bits;
>> +    unsigned int dt_zone_dma_bits;
>> +
>>       acpi_zone_dma_bits = fls64(acpi_iort_dma_get_max_cpu_address());
>>       dt_zone_dma_bits = fls64(of_dma_get_max_cpu_address(NULL));
>>       zone_dma_bits = min3(32U, dt_zone_dma_bits, acpi_zone_dma_bits);
>> @@ -173,8 +173,6 @@ static void __init zone_sizes_init(unsigned long 
>> min, unsigned long max)
>>   #endif
>>   #ifdef CONFIG_ZONE_DMA32
>>       max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
>> -    if (!arm64_dma_phys_limit)
>> -        arm64_dma_phys_limit = dma32_phys_limit;
>>   #endif
>>       max_zone_pfns[ZONE_NORMAL] = max;
>>   @@ -336,8 +334,12 @@ void __init arm64_memblock_init(void)
>>         early_init_fdt_scan_reserved_mem();
>>   -    if (!IS_ENABLED(CONFIG_ZONE_DMA) && 
>> !IS_ENABLED(CONFIG_ZONE_DMA32))
>> +    dma32_phys_limit = max_zone_phys(32);
>> +    if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
>> +        if (IS_ENABLED(CONFIG_ZONE_DMA32))
>> +            arm64_dma_phys_limit = dma32_phys_limit;
>>           reserve_crashkernel();
>> +    }
>>         high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
>>   }
>> @@ -385,7 +387,7 @@ void __init bootmem_init(void)
>>        * request_standard_resources() depends on crashkernel's memory 
>> being
>>        * reserved, so do it here.
>>        */
>> -    if (IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32))
>> +    if (IS_ENABLED(CONFIG_ZONE_DMA))
>>           reserve_crashkernel();
>>         memblock_dump_all();
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index 626ec32873c6..23734481318a 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -529,8 +529,7 @@ static void __init map_mem(pgd_t *pgdp)
>>     #ifdef CONFIG_KEXEC_CORE
>>       if (crash_mem_map) {
>> -        if (IS_ENABLED(CONFIG_ZONE_DMA) ||
>> -            IS_ENABLED(CONFIG_ZONE_DMA32))
>> +        if (IS_ENABLED(CONFIG_ZONE_DMA))
>>               flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
>>           else if (crashk_res.end)
>>               memblock_mark_nomap(crashk_res.start,
>> @@ -571,8 +570,7 @@ static void __init map_mem(pgd_t *pgdp)
>>        * through /sys/kernel/kexec_crash_size interface.
>>        */
>>   #ifdef CONFIG_KEXEC_CORE
>> -    if (crash_mem_map &&
>> -        !IS_ENABLED(CONFIG_ZONE_DMA) && 
>> !IS_ENABLED(CONFIG_ZONE_DMA32)) {
>> +    if (crash_mem_map && !IS_ENABLED(CONFIG_ZONE_DMA)) {
>>           if (crashk_res.end) {
>>               __map_memblock(pgdp, crashk_res.start,
>>                          crashk_res.end + 1,
> .