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Message-ID: <fcb19e22678d126f9c4223d1e80f8c7d27e22692.camel@intel.com>
Date: Fri, 28 Jun 2024 20:58:24 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "tglx@...utronix.de" <tglx@...utronix.de>, "Ashish.Kalra@....com"
<Ashish.Kalra@....com>, "peterz@...radead.org" <peterz@...radead.org>,
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Subject: Re: [PATCH] x86/mm: fix lookup_address() to handle physical memory
holes in direct mapping
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.
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