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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 14.05.24 16:04, Björn Töpel wrote: > From: Björn Töpel > > 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 > --- > 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