From: Baoquan He <bhe@redhat.com>
To: Mike Rapoport <rppt@kernel.org>, Miles Chen <miles.chen@mediatek.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com,
k-hagio-ab@nec.com
Subject: Re: [PATCH] mm/sparse: fix check_usemap_section_nr warnings
Date: Thu, 13 May 2021 09:16:48 +0800 [thread overview]
Message-ID: <20210513011648.GA6776@MiWiFi-R3L-srv> (raw)
In-Reply-To: <YJuh90iYeZ8F4Ain@kernel.org>
On 05/12/21 at 12:37pm, Mike Rapoport wrote:
> On Wed, May 12, 2021 at 01:33:20PM +0800, Miles Chen wrote:
> > On Tue, 2021-05-11 at 13:24 +0300, Mike Rapoport wrote:
> > > On Tue, May 11, 2021 at 05:31:14PM +0800, Miles Chen wrote:
> > > > In current implementation of node_data, if CONFIG_NEED_MULTIPLE_NODES=y,
> > > > node_data is allocated by kzmalloc. If CONFIG_NEED_MULTIPLE_NODES=n,
> > > > we use a global variable named "contig_page_data".
> > > >
> > > > If CONFIG_DEBUG_VIRTUAL is not enabled. __pa() can handle both kzalloc and
> > > > symbol cases. But if CONFIG_DEBUG_VIRTUAL is set, we will have the
> > > > "virt_to_phys used for non-linear address" warning when booting.
> > >
> > > Maybe we'll just allocate pgdat for CONFIG_NEED_MULTIPLE_NODES=n (which is
> > > essentially !NUMA) case in, say, free_area_init()?
> >
> >
> > thanks for your comment.
> >
> > I check the source tree and found that contig_page_data is used by
> > crash_core.c as a symbol. I am not familiar with crash_core but I guess
> > allocate pgdat may break this crash_core users.
> >
> > For example: some userspace scripts want to read the address of
> > contig_page_data symbol from a corefile.
> >
> > kernel/crash_core.c:460: VMCOREINFO_SYMBOL(contig_page_data);
> >
> > #ifndef CONFIG_NEED_MULTIPLE_NODES
> > VMCOREINFO_SYMBOL(mem_map);
> > VMCOREINFO_SYMBOL(contig_page_data);
> > #endif
>
> My understanding is that VMCOREINFO_SYMBOL() should correspond to actual
> symbol. If there is no contig_page_data symbol, there is no need for
> VMCOREINFO_SYMBOL() either.
Yeah, it's exported for makedumpfile and crash utility to parse and get
the memory layout of the corrupted kernel. If removing it, makedumpfile
will get it from node_data[]. Looks like a good idea to unify code for
numa|!numa on pglist_data instances.
Add Kazu to CC since he maintain makedumpfile and Crash utilities.
My concern is that that only happens on arm/arm64/riscv, does it mean the
warning is not necessary, so can be removed? Or we need to check if
CONFIG_DEBUG_VIRTUAL doesn't work well in this case.
Thanks
Baoquan
next prev parent reply other threads:[~2021-05-13 1:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-11 9:31 [PATCH] mm/sparse: fix check_usemap_section_nr warnings Miles Chen
2021-05-11 10:24 ` Mike Rapoport
2021-05-12 5:33 ` Miles Chen
2021-05-12 9:37 ` Mike Rapoport
2021-05-13 1:16 ` Baoquan He [this message]
2021-05-13 2:53 ` Miles Chen
2021-05-19 5:30 ` Mike Rapoport
2021-05-19 7:18 ` Miles Chen
2021-05-19 7:56 ` Mike Rapoport
2021-05-19 8:32 ` Miles Chen
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