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

[Reza Arbab]

On Mon, Dec 19, 2016 at 03:18:07PM +0530, Aneesh Kumar K.V wrote:
>Reza Arbab <arbab at linux.vnet.ibm.com> writes:
>> +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.

>> +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