Reza Arbab <ar...@linux.vnet.ibm.com> writes:
> Tear down and free the four-level page tables of the linear mapping
> during memory hotremove.
>
> We borrow the basic structure of remove_pagetable() and friends from the
> identically-named x86 functions.
>
Can you add more details here, which explain why we don't need to follow
the RCU page table free when doing memory hotunplug ?
> Signed-off-by: Reza Arbab <ar...@linux.vnet.ibm.com>
> ---
> arch/powerpc/include/asm/book3s/64/radix.h | 1 +
> arch/powerpc/mm/pgtable-book3s64.c | 2 +-
> arch/powerpc/mm/pgtable-radix.c | 163
> +++++++++++++++++++++++++++++
> 3 files changed, 165 insertions(+), 1 deletion(-)
>
....
....
> +static void remove_pte_table(pte_t *pte_start, unsigned long addr,
> + unsigned long end)
> +{
> + unsigned long next;
> + pte_t *pte;
> +
> + pte = pte_start + pte_index(addr);
> + for (; addr < end; addr = next, pte++) {
> + next = (addr + PAGE_SIZE) & PAGE_MASK;
> + if (next > end)
> + next = end;
> +
> + if (!pte_present(*pte))
> + continue;
> +
> + spin_lock(&init_mm.page_table_lock);
> + pte_clear(&init_mm, addr, pte);
> + spin_unlock(&init_mm.page_table_lock);
> + }
> +
> + flush_tlb_mm(&init_mm);
Why call a flush here. we do that at the end of remove_page_table .
Isn't that sufficient ?
> +}
> +
> +static void remove_pmd_table(pmd_t *pmd_start, unsigned long addr,
> + unsigned long end, unsigned long map_page_size)
> +{
> + unsigned long next;
> + pte_t *pte_base;
> + pmd_t *pmd;
> +
> + pmd = pmd_start + pmd_index(addr);
> + for (; addr < end; addr = next, pmd++) {
> + next = pmd_addr_end(addr, end);
> +
> + if (!pmd_present(*pmd))
> + continue;
> +
> + if (map_page_size == PMD_SIZE) {
> + spin_lock(&init_mm.page_table_lock);
> + pte_clear(&init_mm, addr, (pte_t *)pmd);
> + spin_unlock(&init_mm.page_table_lock);
> +
> + continue;
> + }
> +
> + pte_base = (pte_t *)pmd_page_vaddr(*pmd);
> + remove_pte_table(pte_base, addr, next);
> + free_pte_table(pte_base, pmd);
> + }
> +}
> +
> +static void remove_pud_table(pud_t *pud_start, unsigned long addr,
> + unsigned long end, unsigned long map_page_size)
> +{
> + unsigned long next;
> + pmd_t *pmd_base;
> + pud_t *pud;
> +
> + pud = pud_start + pud_index(addr);
> + for (; addr < end; addr = next, pud++) {
> + next = pud_addr_end(addr, end);
> +
> + if (!pud_present(*pud))
> + continue;
> +
> + if (map_page_size == PUD_SIZE) {
> + spin_lock(&init_mm.page_table_lock);
> + pte_clear(&init_mm, addr, (pte_t *)pud);
> + spin_unlock(&init_mm.page_table_lock);
> +
> + continue;
> + }
> +
> + pmd_base = (pmd_t *)pud_page_vaddr(*pud);
> + remove_pmd_table(pmd_base, addr, next, map_page_size);
> + free_pmd_table(pmd_base, pud);
> + }
> +}
> +
> +static void remove_pagetable(unsigned long start, unsigned long end,
> + unsigned long map_page_size)
> +{
> + unsigned long next;
> + unsigned long addr;
> + pgd_t *pgd;
> + pud_t *pud;
> +
> + for (addr = start; addr < end; addr = next) {
> + next = pgd_addr_end(addr, end);
> +
> + pgd = pgd_offset_k(addr);
> + if (!pgd_present(*pgd))
> + continue;
> +
> + pud = (pud_t *)pgd_page_vaddr(*pgd);
> + remove_pud_table(pud, addr, next, map_page_size);
> + free_pud_table(pud, pgd);
> + }
> +
> + flush_tlb_mm(&init_mm);
So we want to flush the full kernel tlb when we do a hotplug ?
May be check using flush_tlb_kernel_range(). Also that flush_tlb_mm() do
check for mm_is_thread_local(). Do we update init_mm correct to handle
that check ? I assume we want a tlbie() here instead of tlbiel() ?
> +}
> +
> int radix__create_section_mapping(unsigned long start, unsigned long end)
> {
> unsigned long page_size = 1 << mmu_psize_defs[mmu_linear_psize].shift;
> @@ -482,6 +635,16 @@ int radix__create_section_mapping(unsigned long start,
> unsigned long end)
>
> return 0;
> }
> +
> +int radix__remove_section_mapping(unsigned long start, unsigned long end)
> +{
> + unsigned long page_size = 1 << mmu_psize_defs[mmu_linear_psize].shift;
> +
> + start = _ALIGN_DOWN(start, page_size);
> + remove_pagetable(start, end, page_size);
> +
> + return 0;
> +}
> #endif /* CONFIG_MEMORY_HOTPLUG */
>
> #ifdef CONFIG_SPARSEMEM_VMEMMAP
-aneesh
