Re: [PATCH v3 4/5] powerpc/mm: add radix__remove_section_mapping()

On Mon, Dec 19, 2016 at 03:18:07PM +0530, Aneesh Kumar K.V wrote:

Reza Arbab [off-list ref] writes:

quoted

+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 ?

This was carried over from the x86 version of the function, where they do flush_tlb_all(). I can experiment to make sure things work without it.

quoted

+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() ?

I'll try using flush_tlb_kernel_range() instead. That sure does seem more appropriate.

-- 
Reza Arbab