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

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Date:   Tue, 25 Apr 2017 08:38:42 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>, 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


* 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?

Thanks,

	Ingo