Re: [PATCH] x86/mm: fix lookup_address() to handle physical memory holes in direct mapping

[Tom Lendacky <thomas.lendacky@amd.com>]

On 6/28/24 16:33, Edgecombe, Rick P wrote:
> On Fri, 2024-06-28 at 16:22 -0500, Kalra, Ashish wrote:
>>>> @@ -717,7 +718,11 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd,
>>>> unsigned
>>>> long address,
>>>>         *nx |= pmd_flags(*pmd) & _PAGE_NX;
>>>>         *rw &= pmd_flags(*pmd) & _PAGE_RW;
>>>>  
>>>> -       return pte_offset_kernel(pmd, address);
>>>> +       pte = pte_offset_kernel(pmd, address);
>>>> +       if (pte_none(*pte))
>>>> +               return NULL;
>>>> +
>>>> +       return pte;
>>> The other levels check for pXX_none() before adjusting *level. Not sure what
>>> the
>>> effect would be, but I think it should be the same behavior for all.
>>
>> If we are returning NULL, why should adjusting *level matter.
> 
> Well, I think symmetry is enough of a reason, but actually it should be ok.
> 
> I was looking at this diff compared to my working tree, but this tip commit

Ditto for me.

Thanks,
Tom

> (which is about that scenario) makes it set *level before checking none for all
> of them:
> https://lore.kernel.org/lkml/171871930159.10875.16081839197437299007.tip-bot2@tip-bot2/
> 
> So sorry, nevermind.