Messages in this thread Patch in this message | | | Date | Tue, 11 Dec 2018 17:24:19 +0000 | From | Will Deacon <> | Subject | Re: [PATCH] arm64: Add memory hotplug support |
| |
On Tue, Dec 11, 2018 at 05:21:24PM +0000, Robin Murphy wrote: > On 11/12/2018 16:36, Will Deacon wrote: > > 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? > > The same way every other sparsemem user (apart from arch/arm) does, I guess > - this is literally a copy-paste of the generic pfn_valid() implementation > :/
I don't trust the generic pfn_valid() at all :)
> Given the implementation of __nr_to_section() respective of how > memory_present() and sparse_index_init() set up mem_section in the first > place, I can't see how there can be a problem. You did see the bit 4 lines > above, right?
D'oh, yes, I read that and then instantly forgot it. Ok, so that should be fine.
> > > +#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? > > Bah, James mentioned debug_pagealloc long ago, and I did have a slight > nagging feeling that I was still missing something - yes, I need to fix the > flags for that case. I'm not sure about rodata_full (do you mean > STRICT_KERNEL_RWX?) since a section being added here won't contain kernel > text nor data, and I can't seem to find anywhere that rodata options affect > the linear mapping of plain free RAM.
Ah, we've got code queued on for-next/core so that changing vmalloc() permissions makes the same changes to the linear map.
Will
| |