Messages in this thread Patch in this message | | | Date | Tue, 11 Dec 2018 16:36:05 +0000 | From | Will Deacon <> | Subject | Re: [PATCH] arm64: Add memory hotplug support |
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On Mon, Dec 10, 2018 at 03:29:01PM +0000, Robin Murphy 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> > --- > > Looks like I'm not going to have the whole pte_devmap story figured out > in time to land any ZONE_DEVICE support this cycle, but since this patch > also stands alone as a complete feature (and has ended up remarkably > simple and self-contained), I hope we might consider getting it merged > on its own merit. > > Robin. > > arch/arm64/Kconfig | 3 +++ > arch/arm64/mm/init.c | 8 ++++++++ > arch/arm64/mm/mmu.c | 12 ++++++++++++ > arch/arm64/mm/numa.c | 10 ++++++++++ > 4 files changed, 33 insertions(+) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 6d2b25f51bb3..7b855ae45747 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 2983e0fc1786..82e0b08f2e31 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;
I'm a bit nervous about the call to __nr_to_section() here. How do we ensure that the section number we're passing stays within the bounds of the mem_section array?
> +#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 e1b2d58a311a..22379a74d289 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -1044,3 +1044,15 @@ 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) > +{ > + __create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start), > + size, PAGE_KERNEL, pgd_pgtable_alloc, 0); > + > + return __add_pages(nid, start >> PAGE_SHIFT, size >> PAGE_SHIFT, > + altmap, want_memblock); > +}
If we're mapping the new memory into the linear map, shouldn't we be respecting rodata_full and debug page alloc by forcing page granularity and tweaking the permissions?
Will
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