[PATCH] arm64: move back to generic memblock_enforce_memory_limit()

[Ard Biesheuvel]

On 2 February 2016 at 11:19, Catalin Marinas <catalin.marinas at arm.com> wrote:
> On Mon, Feb 01, 2016 at 07:30:17PM +0100, Ard Biesheuvel wrote:
>>  void __init arm64_memblock_init(void)
>>  {
>>       const s64 linear_region_size = -(s64)PAGE_OFFSET;
>> @@ -215,24 +180,14 @@ void __init arm64_memblock_init(void)
>>       if (memblock_end_of_DRAM() > linear_region_size)
>>               memblock_remove(0, memblock_end_of_DRAM() - linear_region_size);
>>
>> +     /*
>> +      * Apply the memory limit if it was set. Since the kernel may be loaded
>> +      * high up in memory, add back the kernel region that must be accessible
>> +      * via the linear mapping.
>> +      */
>>       if (memory_limit != (phys_addr_t)ULLONG_MAX) {
>> -             u64 kbase = round_down(__pa(_text), MIN_KIMG_ALIGN);
>> -             u64 kend = PAGE_ALIGN(__pa(_end));
>> -             u64 const sz_4g = 0x100000000UL;
>> -
>> -             /*
>> -              * Clip memory in order of preference:
>> -              * - above the kernel and above 4 GB
>> -              * - between 4 GB and the start of the kernel (if the kernel
>> -              *   is loaded high in memory)
>> -              * - between the kernel and 4 GB (if the kernel is loaded
>> -              *   low in memory)
>> -              * - below 4 GB
>> -              */
>> -             clip_mem_range(max(sz_4g, kend), ULLONG_MAX);
>> -             clip_mem_range(sz_4g, kbase);
>> -             clip_mem_range(kend, sz_4g);
>> -             clip_mem_range(0, min(kbase, sz_4g));
>> +             memblock_enforce_memory_limit(memory_limit);
>> +             memblock_add(__pa(__init_begin), (u64)(_end - __init_begin));
>
> Thanks, it looks much simpler now. However, loading the kernel 1GB
> higher with mem=1G fails somewhere during the KVM hyp initialisation. It
> works if I change the last line below to:
>
>         memblock_add(__pa(_text), (u64)(_end - _text));
>

OK, that should work as well.

I suppose the fact that mem= loses some of its accuracy is not an
issue? If you need it to be exact, you should simply not load your
kernel outside your mem= range ...

> I can fold the change in.
>

OK