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 <[email protected]>
---
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 :/
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?
+#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.
Robin.
