Re: [PATCH] x86/mm: fix regression with huge pages on PAE

From: Ingo Molnar <mingo@kernel.org>
To: Borislav Petkov <bp@alien8.de>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com,
	akpm@linux-foundation.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, x86@kernel.org, jgross@suse.com,
	konrad.wilk@oracle.com, elliott@hpe.com,
	boris.ostrovsky@oracle.com, Toshi Kani <toshi.kani@hpe.com>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] x86/mm: fix regression with huge pages on PAE
Date: Thu, 12 Nov 2015 08:48:54 +0100	[thread overview]
Message-ID: <20151112074854.GA5376@gmail.com> (raw)
In-Reply-To: <20151111095101.GA22512@pd.tnic>

* Borislav Petkov <bp@alien8.de> wrote:

> --- a/arch/x86/include/asm/pgtable_types.h
> +++ b/arch/x86/include/asm/pgtable_types.h
> @@ -279,17 +279,14 @@ static inline pmdval_t native_pmd_val(pmd_t pmd)
>  static inline pudval_t pud_pfn_mask(pud_t pud)
>  {
>  	if (native_pud_val(pud) & _PAGE_PSE)
> -		return PUD_PAGE_MASK & PHYSICAL_PAGE_MASK;
> +		return ~((1ULL << PUD_SHIFT) - 1) & PHYSICAL_PAGE_MASK;
>  	else
>  		return PTE_PFN_MASK;
>  }

>  static inline pmdval_t pmd_pfn_mask(pmd_t pmd)
>  {
>  	if (native_pmd_val(pmd) & _PAGE_PSE)
> -		return PMD_PAGE_MASK & PHYSICAL_PAGE_MASK;
> +		return ~((1ULL << PMD_SHIFT) - 1) & PHYSICAL_PAGE_MASK;
>  	else
>  		return PTE_PFN_MASK;
>  }

So instead of uglifying the code, why not fix the real bug: change the 
PMD_PAGE_MASK/PUD_PAGE_MASK definitions to be 64-bit everywhere?

Thanks,

	Ingo