Re: [PATCH] x86/mm: fix lookup_address() to handle physical memory holes in direct mapping
From: Kalra, Ashish
Date: Fri Jun 28 2024 - 17:23:13 EST
On 6/28/2024 3:58 PM, Edgecombe, Rick P wrote:
> On Fri, 2024-06-28 at 20:52 +0000, Ashish Kalra wrote:
>> diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
>> index 443a97e515c0..be8b5bf3bc3f 100644
>> --- a/arch/x86/mm/pat/set_memory.c
>> +++ b/arch/x86/mm/pat/set_memory.c
>> @@ -672,6 +672,7 @@ pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned
>> long address,
>> p4d_t *p4d;
>> pud_t *pud;
>> pmd_t *pmd;
>> + pte_t *pte;
>>
>> *level = PG_LEVEL_256T;
>> *nx = false;
>> @@ -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.
Thanks, Ashish