Re: [PATCH] x86/mm: fix lookup_address() to handle physical memory holes in direct mapping
From: Edgecombe, Rick P
Date: Fri Jun 28 2024 - 16:58:48 EST
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.