linux-kernel - Re: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as EXPORT_SYMBOL

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Message-ID: <CAPcyv4ivyJsyzcbkBWcqBYZMx3VdJF7+VPCNs177DU2rYqtz_A@mail.gmail.com>
Date:   Tue, 7 Jul 2020 21:27:43 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Justin He <Justin.He@....com>
Cc:     Michal Hocko <mhocko@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Catalin Marinas <Catalin.Marinas@....com>,
        Will Deacon <will@...nel.org>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Baoquan He <bhe@...hat.com>,
        Chuhong Yuan <hslester96@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        Kaly Xin <Kaly.Xin@....com>
Subject: Re: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as EXPORT_SYMBOL_GPL

On Tue, Jul 7, 2020 at 9:08 PM Justin He <Justin.He@....com> wrote:
[..]
> > Especially for architectures that use memblock info for numa info
> > (which seems to be everyone except x86) why not implement a generic
> > memory_add_physaddr_to_nid() that does:
> >
> > int memory_add_physaddr_to_nid(u64 addr)
> > {
> >         unsigned long start_pfn, end_pfn, pfn = PHYS_PFN(addr);
> >         int nid;
> >
> >         for_each_online_node(nid) {
> >                 get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
> >                 if (pfn >= start_pfn && pfn <= end_pfn)
> >                         return nid;
> >         }
> >         return NUMA_NO_NODE;
> > }
>
> Thanks for your suggestion,
> Could I wrap the codes and let memory_add_physaddr_to_nid simply invoke
> phys_to_target_node()?

I think it needs to be the reverse. phys_to_target_node() should call
memory_add_physaddr_to_nid() by default, but fall back to searching
reserved memory address ranges in memblock. See phys_to_target_node()
in arch/x86/mm/numa.c. That one uses numa_meminfo instead of memblock,
but the principle is the same i.e. that a target node may not be
represented in memblock.memory, but memblock.reserved. I'm working on
a patch to provide a function similar to get_pfn_range_for_nid() that
operates on reserved memory.