linux-kernel - Re: [PATCH v1 3/9] powerpc/vdso: don't clear PG

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Date:   Mon, 17 Dec 2018 22:38:39 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     David Hildenbrand <david@...hat.com>, linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-m68k@...ts.linux-m68k.org, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        David Hildenbrand <david@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v1 3/9] powerpc/vdso: don't clear PG_reserved

David Hildenbrand <david@...hat.com> writes:

> The VDSO is part of the kernel image and therefore the struct pages are
> marked as reserved during boot.
>
> As we install a special mapping, the actual struct pages will never be
> exposed to MM via the page tables. We can therefore leave the pages
> marked as reserved.
>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Christophe Leroy <christophe.leroy@....fr>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Matthew Wilcox <willy@...radead.org>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  arch/powerpc/kernel/vdso.c | 2 --
>  1 file changed, 2 deletions(-)

Thanks.

Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)

cheers

> diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
> index 65b3bdb99f0b..d59dc2e9a695 100644
> --- a/arch/powerpc/kernel/vdso.c
> +++ b/arch/powerpc/kernel/vdso.c
> @@ -795,7 +795,6 @@ static int __init vdso_init(void)
>  	BUG_ON(vdso32_pagelist == NULL);
>  	for (i = 0; i < vdso32_pages; i++) {
>  		struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
> -		ClearPageReserved(pg);
>  		get_page(pg);
>  		vdso32_pagelist[i] = pg;
>  	}
> @@ -809,7 +808,6 @@ static int __init vdso_init(void)
>  	BUG_ON(vdso64_pagelist == NULL);
>  	for (i = 0; i < vdso64_pages; i++) {
>  		struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
> -		ClearPageReserved(pg);
>  		get_page(pg);
>  		vdso64_pagelist[i] = pg;
>  	}
> -- 
> 2.17.2