linux-kernel - Re: [patch V163 24/51] x86/mm/pti: Add mapping helper functions

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Date:   Mon, 18 Dec 2017 13:52:42 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirsky <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Borislav Petkov <bpetkov@...e.de>,
        Greg KH <gregkh@...uxfoundation.org>, keescook@...gle.com,
        hughd@...gle.com, Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Rik van Riel <riel@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        David Laight <David.Laight@...lab.com>,
        Eduardo Valentin <eduval@...zon.com>, aliguori@...zon.com,
        Will Deacon <will.deacon@....com>, daniel.gruss@...k.tugraz.at,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [patch V163 24/51] x86/mm/pti: Add mapping helper functions

On Mon, Dec 18, 2017 at 12:42:39PM +0100, Thomas Gleixner wrote:
>  static inline void native_set_p4d(p4d_t *p4dp, p4d_t p4d)
>  {
> +#if defined(CONFIG_PAGE_TABLE_ISOLATION) && !defined(CONFIG_X86_5LEVEL)
> +	p4dp->pgd = pti_set_user_pgd(&p4dp->pgd, p4d.pgd);
> +#else
>  	*p4dp = p4d;
> +#endif
>  }
>  
>  static inline void native_p4d_clear(p4d_t *p4d)
> @@ -147,7 +235,11 @@ static inline void native_p4d_clear(p4d_
>  
>  static inline void native_set_pgd(pgd_t *pgdp, pgd_t pgd)
>  {
> +#ifdef CONFIG_PAGE_TABLE_ISOLATION
> +	*pgdp = pti_set_user_pgd(pgdp, pgd);
> +#else
>  	*pgdp = pgd;
> +#endif
>  }

We should probably start using WRITE_ONCE() to set page-table entries.
But that's a whole separate patch series..