On 14.05.24 16:04, Björn Töpel wrote:
From: Björn Töpel <bjorn@xxxxxxxxxxxx>
For an architecture to support memory hotplugging, a couple of
callbacks needs to be implemented:
arch_add_memory()
This callback is responsible for adding the physical memory into the
direct map, and call into the memory hotplugging generic code via
__add_pages() that adds the corresponding struct page entries, and
updates the vmemmap mapping.
arch_remove_memory()
This is the inverse of the callback above.
vmemmap_free()
This function tears down the vmemmap mappings (if
CONFIG_SPARSEMEM_VMEMMAP is enabled), and also deallocates the
backing vmemmap pages. Note that for persistent memory, an
alternative allocator for the backing pages can be used; The
vmem_altmap. This means that when the backing pages are cleared,
extra care is needed so that the correct deallocation method is
used.
arch_get_mappable_range()
This functions returns the PA range that the direct map can map.
Used by the MHP internals for sanity checks.
The page table unmap/teardown functions are heavily based on code from
the x86 tree. The same remove_pgd_mapping() function is used in both
vmemmap_free() and arch_remove_memory(), but in the latter function
the backing pages are not removed.
Signed-off-by: Björn Töpel <bjorn@xxxxxxxxxxxx>
---
arch/riscv/mm/init.c | 242 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 242 insertions(+)
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 6f72b0b2b854..7f0b921a3d3a 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1493,3 +1493,245 @@ void __init pgtable_cache_init(void)
}
}
#endif
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+static void __meminit free_pte_table(pte_t *pte_start, pmd_t *pmd)
+{
+ pte_t *pte;
+ int i;
+
+ for (i = 0; i < PTRS_PER_PTE; i++) {
+ pte = pte_start + i;
+ if (!pte_none(*pte))
+ return;
+ }
+
+ free_pages((unsigned long)page_address(pmd_page(*pmd)), 0);
+ pmd_clear(pmd);
+}
+
+static void __meminit free_pmd_table(pmd_t *pmd_start, pud_t *pud)
+{
+ pmd_t *pmd;
+ int i;
+
+ for (i = 0; i < PTRS_PER_PMD; i++) {
+ pmd = pmd_start + i;
+ if (!pmd_none(*pmd))
+ return;
+ }
+
+ free_pages((unsigned long)page_address(pud_page(*pud)), 0);
+ pud_clear(pud);
+}
+
+static void __meminit free_pud_table(pud_t *pud_start, p4d_t *p4d)
+{
+ pud_t *pud;
+ int i;
+
+ for (i = 0; i < PTRS_PER_PUD; i++) {
+ pud = pud_start + i;
+ if (!pud_none(*pud))
+ return;
+ }
+
+ free_pages((unsigned long)page_address(p4d_page(*p4d)), 0);
+ p4d_clear(p4d);
+}
+
+static void __meminit free_vmemmap_storage(struct page *page, size_t size,
+ struct vmem_altmap *altmap)
+{
+ if (altmap)
+ vmem_altmap_free(altmap, size >> PAGE_SHIFT);
+ else
+ free_pages((unsigned long)page_address(page), get_order(size));
If you unplug a DIMM that was added during boot (can happen on x86-64,
can it happen on riscv?), free_pages() would not be sufficient. You'd be
freeing a PG_reserved page that has to be freed differently.
--
Cheers,
David / dhildenb
