linux-kernel - Re: [PATCH AUTOSEL 4.14 62/95] mm, memory_hotplug: initialize struct pages for the full memory section

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Message-ID: <20190507175133.GV31017@dhcp22.suse.cz>
Date:   Tue, 7 May 2019 19:51:33 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Sasha Levin <sashal@...nel.org>,
        Alexander Duyck <alexander.duyck@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>,
        Mikhail Zaslonko <zaslonko@...ux.ibm.com>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Pasha Tatashin <Pavel.Tatashin@...rosoft.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sasha Levin <alexander.levin@...rosoft.com>,
        linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH AUTOSEL 4.14 62/95] mm, memory_hotplug: initialize struct
 pages for the full memory section

On Tue 07-05-19 10:43:31, Linus Torvalds wrote:
> On Tue, May 7, 2019 at 10:36 AM Matthew Wilcox <willy@...radead.org> wrote:
> >
> > Can we do something with qemu?  Is it flexible enough to hotplug memory
> > at the right boundaries?
> 
> It's not just the actual hotplugged memory, it's things like how the
> e820 tables were laid out for the _regular_ non-hotplug stuff too,
> iirc to get the cases where something didn't work out.
> 
> I'm sure it *could* be emulated, and I'm sure some hotplug (and page
> poison errors etc) testing in qemu would be lovely and presumably some
> people do it, but all the cases so far have been about odd small
> special cases that people didn't think of and didn't hit. I'm not sure
> the qemu testing would think of them either..

Yes, this is exactly my point. It would be great to have those odd small
special cases that we have met already available though. For a
regression testing for them at least.
-- 
Michal Hocko
SUSE Labs