Re: [PATCH 8/10] memory-hotplug : remove page table of x86_64 architecture

Wen Congyang
2012-10-08T05:23:32Z

At 10/08/2012 12:37 PM, Andi Kleen Wrote:
> Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> writes:
>> + }
>> +
>> + /*
>> + * We use 2M page, but we need to remove part of them,
>> + * so split 2M page to 4K page.
>> + */
>> + pte = alloc_low_page(&pte_phys);
>
> What happens when the allocation fails?
>
> alloc_low_page seems to be buggy there too, it would __pa a NULL
> pointer.

Yes, it will cause kernek panicked in __pa() if CONFI_DEBUG_VIRTUAL is set.
Otherwise, it will return a NULL pointer. I will update this patch to deal
with NULL pointer.

>
>> + if (pud_large(*pud)) {
>> + if ((addr & ~PUD_MASK) == 0 && next <= end) {
>> + set_pud(pud, __pud(0));
>> + pages++;
>> + continue;
>> + }
>> +
>> + /*
>> + * We use 1G page, but we need to remove part of them,
>> + * so split 1G page to 2M page.
>> + */
>> + pmd = alloc_low_page(&pmd_phys);
>
> Same here
>
>> + __split_large_page((pte_t *)pud, addr, (pte_t *)pmd);
>> +
>> + spin_lock(&init_mm.page_table_lock);
>> + pud_populate(&init_mm, pud, __va(pmd_phys));
>> + spin_unlock(&init_mm.page_table_lock);
>> + }
>> +
>> + pmd = map_low_page(pmd_offset(pud, 0));
>> + phys_pmd_remove(pmd, addr, end);
>> + unmap_low_page(pmd);
>> + __flush_tlb_all();
>> + }
>> + __flush_tlb_all();
>
> This doesn't flush the other CPUs doesn't it?

How to flush the other CPU's tlb? use on_each_cpu() to run __flush_tlb_all()
on each online cpu?

Thanks
Wen Congyang

>
> -Andi
>