From: Andrew Morton <akpm@linux-foundation.org>
To: zhong jiang <zhongjiang@huawei.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
linux-mm@kvack.org, Alexander Potapenko <glider@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
kasan-dev@googlegroups.com
Subject: Re: [PATCH] mm: add restriction when memory_hotplug config enable
Date: Thu, 4 Aug 2016 13:08:03 -0700 [thread overview]
Message-ID: <20160804130803.de357aa080482bc3977c77ce@linux-foundation.org> (raw)
In-Reply-To: <57A186C6.9050301@huawei.com>
On Wed, 3 Aug 2016 13:53:10 +0800 zhong jiang <zhongjiang@huawei.com> wrote:
> On 2016/8/2 18:40, Andrey Ryabinin wrote:
> >
> > On 08/01/2016 10:54 PM, Andrew Morton wrote:
> >> On Mon, 1 Aug 2016 23:00:51 +0800 zhongjiang <zhongjiang@huawei.com> wrote:
> >>
> >>> From: zhong jiang <zhongjiang@huawei.com>
> >>>
> >>> At present, It is obvious that memory online and offline will fail
> >>> when KASAN enable,
> >> huh, I didn't know that.
> > Ahem... https://lkml.kernel.org/r/<20150130133552.580f73b97a9bd007979b5419@linux-foundation.org>
> >
> > Also
> >
> > commit 786a8959912eb94fc2381c2ae487a96ce55dabca
> > kasan: disable memory hotplug
> >
> > Currently memory hotplug won't work with KASan. As we don't have shadow
> > for hotplugged memory, kernel will crash on the first access to it. To
> > make this work we will need to allocate shadow for new memory.
> >
> > At some future point proper memory hotplug support will be implemented.
> > Until then, print a warning at startup and disable memory hot-add.
> >
> >
> >
> >> What's the problem and are there plans to fix it?
> > Nobody complained, so I didn't bother to fix it.
> > The fix for this should be simple, I'll look into this.
> >
> >>> therefore, it is necessary to add the condition
> >>> to limit the memory_hotplug when KASAN enable.
> >>>
> > I don't understand why we need Kconfig dependency.
> > Why is that better than runtime warn message?
> The user rarely care about the runtime warn message when the
> system is good running. In fact, They are confilct with each other.
> For me, I know the reason. but I always forget to do so. As a result,
> I test the memory hotplug fails again. so, I hope to add the explicit dependency.
Yes, I think it's better to disable the configuration than to permit
people to run known-to-be-broken kernel setups - that will just cause
confusion and pointless bug reports. Let's undo the Kconfig change
when this gets fixed up.
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prev parent reply other threads:[~2016-08-04 20:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-01 15:00 zhongjiang
2016-08-01 19:54 ` Andrew Morton
2016-08-02 1:41 ` zhong jiang
2016-08-02 10:40 ` Andrey Ryabinin
2016-08-03 5:53 ` zhong jiang
2016-08-04 20:08 ` Andrew Morton [this message]
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