linux-kernel - Re: [PATCH RFC 3/6] kexec: export PG

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Message-ID: <20181115111023.GC26448@zn.tnic>
Date:   Thu, 15 Nov 2018 12:10:23 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Dave Young <dyoung@...hat.com>
Cc:     David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        devel@...uxdriverproject.org, linux-fsdevel@...r.kernel.org,
        linux-pm@...r.kernel.org, xen-devel@...ts.xenproject.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Baoquan He <bhe@...hat.com>, Omar Sandoval <osandov@...com>,
        Arnd Bergmann <arnd@...db.de>,
        Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...e.com>,
        Lianbo Jiang <lijiang@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH RFC 3/6] kexec: export PG_offline to VMCOREINFO

On Thu, Nov 15, 2018 at 02:19:23PM +0800, Dave Young wrote:
> It would be good to copy some background info from cover letter to the
> patch description so that we can get better understanding why this is
> needed now.
> 
> BTW, Lianbo is working on a documentation of the vmcoreinfo exported
> fields. Ccing him so that he is aware of this.
> 
> Also cc Boris,  although I do not want the doc changes blocks this
> he might have different opinion :)

Yeah, my initial reaction is that exporting an mm-internal flag to
userspace is a no-no.

What would be better, IMHO, is having a general method of telling the
kdump kernel - maybe ranges of physical addresses - which to skip.

Because the moment there's a set of pages which do not have PG_offline
set but kdump would still like to skip, this breaks.

But that's mm guys' call.

-- 
Regards/Gruss,
    Boris.

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