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

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Message-ID: <20151112075758.GA20702@node.shutemov.name>
Date:	Thu, 12 Nov 2015 09:57:58 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Borislav Petkov <bp@...en8.de>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com,
	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, x86@...nel.org, jgross@...e.com,
	konrad.wilk@...cle.com, elliott@....com,
	boris.ostrovsky@...cle.com, Toshi Kani <toshi.kani@....com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] x86/mm: fix regression with huge pages on PAE

On Thu, Nov 12, 2015 at 08:48:54AM +0100, Ingo Molnar wrote:
> 
> * Borislav Petkov <bp@...en8.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?

*PAGE_MASK are usually applied to virtual addresses. I don't think it
should anything but 'unsigned long'. This is odd use case really.

-- 
 Kirill A. Shutemov
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