linux-kernel - Re: [PATCH v1 0/2] mm/kdump: exclude reserved pages in dumps

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Date:   Mon, 23 Jul 2018 13:45:18 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     David Hildenbrand <david@...hat.com>, linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Baoquan He <bhe@...hat.com>, Dave Young <dyoung@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hari Bathini <hbathini@...ux.vnet.ibm.com>,
        Huang Ying <ying.huang@...el.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Marc-André Lureau <marcandre.lureau@...hat.com>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Michal Hocko <mhocko@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        Miles Chen <miles.chen@...iatek.com>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Petr Tesarik <ptesarik@...e.cz>
Subject: Re: [PATCH v1 0/2] mm/kdump: exclude reserved pages in dumps

On 07/20/2018 02:34 PM, David Hildenbrand wrote:
> Dumping tools (like makedumpfile) right now don't exclude reserved pages.
> So reserved pages might be access by dump tools although nobody except
> the owner should touch them.

Are you sure about that? Or maybe I understand wrong. Maybe it changed
recently, but IIRC pages that are backing memmap (struct pages) are also
PG_reserved. And you definitely do want those in the dump.

> This is relevant in virtual environments where we soon might want to
> report certain reserved pages to the hypervisor and they might no longer
> be accessible - what already was documented for reserved pages a long
> time ago ("might not even exist").
> 
> David Hildenbrand (2):
>   mm: clarify semantics of reserved pages
>   kdump: include PG_reserved value in VMCOREINFO
> 
>  include/linux/page-flags.h | 4 ++--
>  kernel/crash_core.c        | 1 +
>  2 files changed, 3 insertions(+), 2 deletions(-)
>