linux-kernel - Re: [PATCH 12/16] x86/mm/pae: Populate the user page-table with user pgd's

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Date:   Tue, 16 Jan 2018 20:44:24 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Brian Gerst <brgerst@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Eduardo Valentin <eduval@...zon.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Will Deacon <will.deacon@....com>, aliguori@...zon.com,
        daniel.gruss@...k.tugraz.at, hughd@...gle.com, keescook@...gle.com,
        Andrea Arcangeli <aarcange@...hat.com>,
        Waiman Long <llong@...hat.com>, jroedel@...e.de
Subject: Re: [PATCH 12/16] x86/mm/pae: Populate the user page-table with user
 pgd's

On Tue, Jan 16, 2018 at 10:11:14AM -0800, Dave Hansen wrote:
> 
> Ugh.  The ghosts of PAE have come back to haunt us.

:-) Yeah, PAE caused the most trouble for me while getting this running.

> 
> Could we do:
> 
> static inline bool pgd_supports_nx(unsigned long)
> {
> #ifdef CONFIG_X86_64
> 	return (__supported_pte_mask & _PAGE_NX);
> #else
> 	/* No 32-bit page tables support NX at PGD level */
> 	return 0;
> #endif
> }
> 
> Nobody will ever spot the #ifdef the way you laid it out.

Right, thats a better way to do it. I'll change it in the next version.

Thanks,

	Joerg