Re: [PATCH] x86/mm/pti: in pti_clone_pgtable() don't increase addr by PUD_SIZE

Song Liu
2019-08-20T13:21:45Z

> On Aug 20, 2019, at 4:16 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Tue, 20 Aug 2019, Peter Zijlstra wrote:
>> What that code wants to do is skip to the end of the pud, a pmd_size
>> increase will not do that. And right below this, there's a second
>> instance of this exact pattern.
>>
>> Did I get the below right?
>>
>> ---
>> diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
>> index b196524759ec..32b20b3cb227 100644
>> --- a/arch/x86/mm/pti.c
>> +++ b/arch/x86/mm/pti.c
>> @@ -330,12 +330,14 @@ pti_clone_pgtable(unsigned long start, unsigned long end,
>>
>> pud = pud_offset(p4d, addr);
>> if (pud_none(*pud)) {
>> + addr &= PUD_MASK;
>> addr += PUD_SIZE;
>
> round_up(addr, PUD_SIZE);

I guess we need "round_up(addr + PMD_SIZE, PUD_SIZE)".

Thanks,
Song

>
> perhaps?
>
>> continue;
>> }
>>
>> pmd = pmd_offset(pud, addr);
>> if (pmd_none(*pmd)) {
>> + addr &= PMD_MASK;
>> addr += PMD_SIZE;
>> continue;
>> }
>>