Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751444AbeAPVK7 (ORCPT <rfc822;ralf@linux-mips.org> + 1 other);
        Tue, 16 Jan 2018 16:10:59 -0500
Received: from Galois.linutronix.de ([146.0.238.70]:44332 "EHLO
        Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1750772AbeAPVK6 (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 16 Jan 2018 16:10:58 -0500
Date: Tue, 16 Jan 2018 22:10:52 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Joerg Roedel <joro@8bytes.org>
cc: Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>,
        x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Juergen Gross <jgross@suse.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Borislav Petkov <bp@alien8.de>, Jiri Kosina <jkosina@suse.cz>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Brian Gerst <brgerst@gmail.com>,
        David Laight <David.Laight@aculab.com>,
        Denys Vlasenko <dvlasenk@redhat.com>,
        Eduardo Valentin <eduval@amazon.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Will Deacon <will.deacon@arm.com>, aliguori@amazon.com,
        daniel.gruss@iaik.tugraz.at, hughd@google.com, keescook@google.com,
        Andrea Arcangeli <aarcange@redhat.com>,
        Waiman Long <llong@redhat.com>, jroedel@suse.de
Subject: Re: [PATCH 12/16] x86/mm/pae: Populate the user page-table with user
 pgd's
In-Reply-To: <1516120619-1159-13-git-send-email-joro@8bytes.org>
Message-ID: <alpine.DEB.2.20.1801162207460.2366@nanos>
References: <1516120619-1159-1-git-send-email-joro@8bytes.org> <1516120619-1159-13-git-send-email-joro@8bytes.org>
User-Agent: Alpine 2.20 (DEB 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
X-Linutronix-Spam-Score: -1.0
X-Linutronix-Spam-Level: -
X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required,  ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Return-Path: <linux-kernel-owner@vger.kernel.org>

On Tue, 16 Jan 2018, Joerg Roedel wrote:
>  
> +#ifdef CONFIG_X86_64
>  	/*
>  	 * If this is normal user memory, make it NX in the kernel
>  	 * pagetables so that, if we somehow screw up and return to
> @@ -134,10 +135,16 @@ pgd_t __pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
>  	 *     may execute from it
>  	 *  - we don't have NX support
>  	 *  - we're clearing the PGD (i.e. the new pgd is not present).
> +	 *  - We run on a 32 bit kernel. 2-level paging doesn't support NX at
> +	 *    all and PAE paging does not support it on the PGD level. We can
> +	 *    set it in the PMD level there in the future, but that means we
> +	 *    need to unshare the PMDs between the kernel and the user
> +	 *    page-tables.
>  	 */
>  	if ((pgd.pgd & (_PAGE_USER|_PAGE_PRESENT)) == (_PAGE_USER|_PAGE_PRESENT) &&
>  	    (__supported_pte_mask & _PAGE_NX))
>  		pgd.pgd |= _PAGE_NX;

I'd suggest to have:

static inline pteval_t supported_pgd_mask(void)
{
	if (IS_ENABLED(CONFIG_X86_64))
		return __supported_pte_mask;
	return __supported_pte_mask & ~_PAGE_NX);
}

and get rid of the ifdeffery completely.

Thanks,

	tglx