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SubjectRe: [PATCH v2] arm64: Add memory hotplug support
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On 12/12/2018 11:42, Jonathan Cameron wrote:
> On Tue, 11 Dec 2018 18:48:48 +0000
> Robin Murphy <robin.murphy@arm.com> wrote:
>
>> Wire up the basic support for hot-adding memory. Since memory hotplug
>> is fairly tightly coupled to sparsemem, we tweak pfn_valid() to also
>> cross-check the presence of a section in the manner of the generic
>> implementation, before falling back to memblock to check for no-map
>> regions within a present section as before. By having arch_add_memory(()
>> create the linear mapping first, this then makes everything work in the
>> way that __add_section() expects.
>>
>> We expect hotplug to be ACPI-driven, so the swapper_pg_dir updates
>> should be safe from races by virtue of the global device hotplug lock.
>>
>> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> Hi Robin,
>
> What tree is this against?
>
> rodata_full doesn't seem be exist for me on 4.20-rc6.

Sorry, this is now based on the arm64 for-next/core branch - I was
similarly confused when Will first mentioned rodata_full on v1 ;)

> With v1 I did the 'new node' test and it looked good except for an
> old cgroups warning that has always been there (and has been on my list
> to track down for a long time).

Great, thanks for testing!

Robin.

>
> Jonathan
>> ---
>>
>> v2: Handle page-mappings-only cases appropriately
>>
>> arch/arm64/Kconfig | 3 +++
>> arch/arm64/mm/init.c | 8 ++++++++
>> arch/arm64/mm/mmu.c | 17 +++++++++++++++++
>> arch/arm64/mm/numa.c | 10 ++++++++++
>> 4 files changed, 38 insertions(+)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 4dbef530cf58..be423fda5cec 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -261,6 +261,9 @@ config ZONE_DMA32
>> config HAVE_GENERIC_GUP
>> def_bool y
>>
>> +config ARCH_ENABLE_MEMORY_HOTPLUG
>> + def_bool y
>> +
>> config SMP
>> def_bool y
>>
>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>> index 6cde00554e9b..4bfe0fc9edac 100644
>> --- a/arch/arm64/mm/init.c
>> +++ b/arch/arm64/mm/init.c
>> @@ -291,6 +291,14 @@ int pfn_valid(unsigned long pfn)
>>
>> if ((addr >> PAGE_SHIFT) != pfn)
>> return 0;
>> +
>> +#ifdef CONFIG_SPARSEMEM
>> + if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
>> + return 0;
>> +
>> + if (!valid_section(__nr_to_section(pfn_to_section_nr(pfn))))
>> + return 0;
>> +#endif
>> return memblock_is_map_memory(addr);
>> }
>> EXPORT_SYMBOL(pfn_valid);
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index 674c409a8ce4..da513a1facf4 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -1046,3 +1046,20 @@ int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
>> pmd_free(NULL, table);
>> return 1;
>> }
>> +
>> +#ifdef CONFIG_MEMORY_HOTPLUG
>> +int arch_add_memory(int nid, u64 start, u64 size, struct vmem_altmap *altmap,
>> + bool want_memblock)
>> +{
>> + int flags = 0;
>> +
>> + if (rodata_full || debug_pagealloc_enabled())
>> + flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
>> +
>> + __create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start),
>> + size, PAGE_KERNEL, pgd_pgtable_alloc, flags);
>> +
>> + return __add_pages(nid, start >> PAGE_SHIFT, size >> PAGE_SHIFT,
>> + altmap, want_memblock);
>> +}
>> +#endif
>> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
>> index 27a31efd9e8e..ae34e3a1cef1 100644
>> --- a/arch/arm64/mm/numa.c
>> +++ b/arch/arm64/mm/numa.c
>> @@ -466,3 +466,13 @@ void __init arm64_numa_init(void)
>>
>> numa_init(dummy_numa_init);
>> }
>> +
>> +/*
>> + * We hope that we will be hotplugging memory on nodes we already know about,
>> + * such that acpi_get_node() succeeds and we never fall back to this...
>> + */
>> +int memory_add_physaddr_to_nid(u64 addr)
>> +{
>> + pr_warn("Unknown node for memory at 0x%llx, assuming node 0\n", addr);
>> + return 0;
>> +}
>
>

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