linux-kernel - Re: [PATCH 05/23] x86, kaiser: unmap kernel from userspace page tables (core patch)

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Date:   Fri, 5 Jan 2018 11:03:56 -0800
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Yisheng Xie <xieyisheng1@...wei.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, richard.fellner@...dent.tugraz.at,
        moritz.lipp@...k.tugraz.at, daniel.gruss@...k.tugraz.at,
        michael.schwarz@...k.tugraz.at, luto@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        keescook@...gle.com, hughd@...gle.com, x86@...nel.org,
        Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH 05/23] x86, kaiser: unmap kernel from userspace page
 tables (core patch)

On 01/05/2018 10:19 AM, Jiri Kosina wrote:
> --- a/arch/x86/platform/efi/efi_64.c
> +++ b/arch/x86/platform/efi/efi_64.c
> @@ -95,6 +95,12 @@ pgd_t * __init efi_call_phys_prolog(void
>  		save_pgd[pgd] = *pgd_offset_k(pgd * PGDIR_SIZE);
>  		vaddress = (unsigned long)__va(pgd * PGDIR_SIZE);
>  		set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), *pgd_offset_k(vaddress));
> +		/*
> +		 * pgprot API doesn't clear it for PGD
> +		 *
> +		 * Will be brought back automatically in _epilog()
> +		 */
> +		pgd_offset_k(pgd * PGDIR_SIZE)->pgd &= ~_PAGE_NX;
>  	}
>  	__flush_tlb_all();

Wait a sec...  Where does the _PAGE_USER come from?  Shouldn't we see
the &init_mm in there and *not* set _PAGE_USER?