On Tue, May 14, 2024 at 4:05 PM Björn Töpel <bj...@kernel.org> wrote: > > From: Björn Töpel <bj...@rivosinc.com> > > 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 <bj...@rivosinc.com> > --- > 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)); > +} > + > +static void __meminit remove_pte_mapping(pte_t *pte_base, unsigned long > addr, unsigned long end, > + bool is_vmemmap, struct vmem_altmap > *altmap) > +{ > + unsigned long next; > + pte_t *ptep, pte; > + > + for (; addr < end; addr = next) { > + next = (addr + PAGE_SIZE) & PAGE_MASK; > + if (next > end) > + next = end; > + > + ptep = pte_base + pte_index(addr); > + pte = READ_ONCE(*ptep); > + > + if (!pte_present(*ptep)) > + continue; > + > + pte_clear(&init_mm, addr, ptep); > + if (is_vmemmap) > + free_vmemmap_storage(pte_page(pte), PAGE_SIZE, > altmap); > + } > +} > + > +static void __meminit remove_pmd_mapping(pmd_t *pmd_base, unsigned long > addr, unsigned long end, > + bool is_vmemmap, struct vmem_altmap > *altmap) > +{ > + unsigned long next; > + pte_t *pte_base; > + pmd_t *pmdp, pmd; > + > + for (; addr < end; addr = next) { > + next = pmd_addr_end(addr, end); > + pmdp = pmd_base + pmd_index(addr); > + pmd = READ_ONCE(*pmdp); > + > + if (!pmd_present(pmd)) > + continue; > + > + if (pmd_leaf(pmd)) { > + pmd_clear(pmdp); > + if (is_vmemmap) > + free_vmemmap_storage(pmd_page(pmd), PMD_SIZE, > altmap); > + continue; > + } > + > + pte_base = (pte_t *)pmd_page_vaddr(*pmdp); > + remove_pte_mapping(pte_base, addr, next, is_vmemmap, altmap); > + free_pte_table(pte_base, pmdp); > + } > +} > + > +static void __meminit remove_pud_mapping(pud_t *pud_base, unsigned long > addr, unsigned long end, > + bool is_vmemmap, struct vmem_altmap > *altmap) > +{ > + unsigned long next; > + pud_t *pudp, pud; > + pmd_t *pmd_base; > + > + for (; addr < end; addr = next) { > + next = pud_addr_end(addr, end); > + pudp = pud_base + pud_index(addr); > + pud = READ_ONCE(*pudp); > + > + if (!pud_present(pud)) > + continue; > + > + if (pud_leaf(pud)) { > + if (pgtable_l4_enabled) { > + pud_clear(pudp); > + if (is_vmemmap) > + free_vmemmap_storage(pud_page(pud), > PUD_SIZE, altmap); > + } > + continue; > + } > + > + pmd_base = pmd_offset(pudp, 0); > + remove_pmd_mapping(pmd_base, addr, next, is_vmemmap, altmap); > + > + if (pgtable_l4_enabled) > + free_pmd_table(pmd_base, pudp); > + } > +} > + > +static void __meminit remove_p4d_mapping(p4d_t *p4d_base, unsigned long > addr, unsigned long end, > + bool is_vmemmap, struct vmem_altmap > *altmap) > +{ > + unsigned long next; > + p4d_t *p4dp, p4d; > + pud_t *pud_base; > + > + for (; addr < end; addr = next) { > + next = p4d_addr_end(addr, end); > + p4dp = p4d_base + p4d_index(addr); > + p4d = READ_ONCE(*p4dp); > + > + if (!p4d_present(p4d)) > + continue; > + > + if (p4d_leaf(p4d)) { > + if (pgtable_l5_enabled) { > + p4d_clear(p4dp); > + if (is_vmemmap) > + free_vmemmap_storage(p4d_page(p4d), > P4D_SIZE, altmap); > + } > + continue; > + } > + > + pud_base = pud_offset(p4dp, 0); > + remove_pud_mapping(pud_base, addr, next, is_vmemmap, altmap); > + > + if (pgtable_l5_enabled) > + free_pud_table(pud_base, p4dp); > + } > +} > + > +static void __meminit remove_pgd_mapping(unsigned long va, unsigned long > end, bool is_vmemmap, > + struct vmem_altmap *altmap) > +{ > + unsigned long addr, next; > + p4d_t *p4d_base; > + pgd_t *pgd; > + > + for (addr = va; addr < end; addr = next) { > + next = pgd_addr_end(addr, end); > + pgd = pgd_offset_k(addr); > + > + if (!pgd_present(*pgd)) > + continue; > + > + if (pgd_leaf(*pgd)) > + continue; > + > + p4d_base = p4d_offset(pgd, 0); > + remove_p4d_mapping(p4d_base, addr, next, is_vmemmap, altmap); > + } > + > + flush_tlb_all(); > +} > + > +static void __meminit remove_linear_mapping(phys_addr_t start, u64 size) > +{ > + unsigned long va = (unsigned long)__va(start); > + unsigned long end = (unsigned long)__va(start + size); > + > + remove_pgd_mapping(va, end, false, NULL); > +} > + > +struct range arch_get_mappable_range(void) > +{ > + struct range mhp_range; > + > + mhp_range.start = __pa(PAGE_OFFSET); > + mhp_range.end = __pa(PAGE_END - 1); > + return mhp_range; > +} > + > +int __ref arch_add_memory(int nid, u64 start, u64 size, struct mhp_params > *params) > +{ > + int ret; > + > + create_linear_mapping_range(start, start + size, 0, ¶ms->pgprot); > + flush_tlb_all(); > + ret = __add_pages(nid, start >> PAGE_SHIFT, size >> PAGE_SHIFT, > params); > + if (ret) { > + remove_linear_mapping(start, size); > + return ret; > + } > +
You need to flush the TLB here too since __add_pages() populates the page table with the new vmemmap mapping (only because riscv allows to cache invalid entries, I'll adapt this in my next version of Svvptc support). > + max_pfn = PFN_UP(start + size); > + max_low_pfn = max_pfn; > + return 0; > +} > + > +void __ref arch_remove_memory(u64 start, u64 size, struct vmem_altmap > *altmap) > +{ > + __remove_pages(start >> PAGE_SHIFT, size >> PAGE_SHIFT, altmap); > + remove_linear_mapping(start, size); You need to flush the TLB here too. > +} > + > +#ifdef CONFIG_SPARSEMEM_VMEMMAP > +void __ref vmemmap_free(unsigned long start, unsigned long end, struct > vmem_altmap *altmap) > +{ > + remove_pgd_mapping(start, end, true, altmap); > +} > +#endif /* CONFIG_SPARSEMEM_VMEMMAP */ > +#endif /* CONFIG_MEMORY_HOTPLUG */ > -- > 2.40.1 >