linux-kernel - Re: [tip:x86/mm] x86: Convert the rest of the code to support p4d

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Message-ID: <20170425090242.sgxzammvowv7cezs@node.shutemov.name>
Date:   Tue, 25 Apr 2017 12:02:42 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>, dvlasenk@...hat.com,
        Andy Lutomirski <luto@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>, brgerst@...il.com,
        Arnd Bergmann <arnd@...db.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Michal Hocko <mhocko@...e.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...en8.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/mm] x86: Convert the rest of the code to support p4d_t

On Tue, Apr 25, 2017 at 08:38:42AM +0200, Ingo Molnar wrote:
> 
> * Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> wrote:
> 
> > On Mon, Apr 24, 2017 at 11:42:34AM -0700, Dan Williams wrote:
> > > >
> > > > I cannot reproduce the issue.
> > > >
> > > > Could you share your kernel kernel config?
> > > 
> > > Kernel config available here:
> > > https://gist.github.com/djbw/2b99a014396cca9f4406586573be98c0
> > 
> > Patch below should help. Please check.
> > 
> > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> > index a242139df8fe..745e5e183169 100644
> > --- a/arch/x86/mm/init_64.c
> > +++ b/arch/x86/mm/init_64.c
> > @@ -962,7 +962,7 @@ remove_pud_table(pud_t *pud_start, unsigned long addr, unsigned long end,
> >  			continue;
> >  		}
> >  
> > -		pmd_base = (pmd_t *)pud_page_vaddr(*pud);
> > +		pmd_base = pmd_offset(pud, 0);
> >  		remove_pmd_table(pmd_base, addr, next, direct);
> >  		free_pmd_table(pmd_base, pud);
> >  	}
> > @@ -988,7 +988,7 @@ remove_p4d_table(p4d_t *p4d_start, unsigned long addr, unsigned long end,
> >  
> >  		BUILD_BUG_ON(p4d_large(*p4d));
> >  
> > -		pud_base = (pud_t *)p4d_page_vaddr(*p4d);
> > +		pud_base = pud_offset(p4d, 0);
> >  		remove_pud_table(pud_base, addr, next, direct);
> >  		free_pud_table(pud_base, p4d);
> >  	}
> > @@ -1013,7 +1013,7 @@ remove_pagetable(unsigned long start, unsigned long end, bool direct)
> >  		if (!pgd_present(*pgd))
> >  			continue;
> >  
> > -		p4d = (p4d_t *)pgd_page_vaddr(*pgd);
> > +		p4d = p4d_offset(pgd, 0);
> >  		remove_p4d_table(p4d, addr, next, direct);
> >  	}
> 
> Type casts are dangerous, chapter 378. I missed them when applying the patches.
> 
> Could you please double-check all other type casts introduced by the 5-level 
> paging patches, to make sure it's all using natural type conversions?

I looked though at the rest of (p4d_t) and (p4d_t *) casts and they look
okay: under pgd_none()/!pgd_preset() or within #if PTRS_PER_P4d > 1.

I'll prepare proper patch.

-- 
 Kirill A. Shutemov