Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as
 EXPORT_SYMBOL_GPL
To:     Mike Rapoport <rppt@linux.ibm.com>,
        Dan Williams <dan.j.williams@intel.com>
Cc:     Michal Hocko <mhocko@kernel.org>, Jia He <justin.he@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Baoquan He <bhe@redhat.com>,
        Chuhong Yuan <hslester96@gmail.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        linux-nvdimm <linux-nvdimm@lists.01.org>,
        Kaly Xin <Kaly.Xin@arm.com>
References: <20200707055917.143653-1-justin.he@arm.com>
 <20200707055917.143653-2-justin.he@arm.com>
 <20200707115454.GN5913@dhcp22.suse.cz> <20200707121302.GB9411@linux.ibm.com>
 <474f93e7-c709-1a13-5418-29f1777f614c@redhat.com>
 <20200707180043.GA386073@linux.ibm.com>
 <CAPcyv4iB-vP8U4pH_3jptfODbiNqJZXoTmA6+7EHoddk9jBgEQ@mail.gmail.com>
 <20200708052626.GB386073@linux.ibm.com>
From:   David Hildenbrand <david@redhat.com>
Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata=
 mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ
 dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL
 QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp
 XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK
 Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9
 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt
 WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc
 UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv
 jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb
 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk
 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI
 AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q
 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw
 zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s
 Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ
 jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x
 II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U
 Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e
 RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/
 ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC
 Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ
 ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz
 Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb
 T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A
 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk
 CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G
 NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75
 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx
 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS
 lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv
 AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa
 N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q
 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv
 GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y
 GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t
 H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp
 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ
 ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz
 GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU
 CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB
 njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX
 FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg=
Organization: Red Hat GmbH
Message-ID: <9a009cf6-6c30-91ca-a1a5-9aa090c66631@redhat.com>
Date:   Wed, 8 Jul 2020 09:21:25 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.9.0
MIME-Version: 1.0
In-Reply-To: <20200708052626.GB386073@linux.ibm.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 08.07.20 07:27, Mike Rapoport wrote:
> On Tue, Jul 07, 2020 at 03:05:48PM -0700, Dan Williams wrote:
>> On Tue, Jul 7, 2020 at 11:01 AM Mike Rapoport <rppt@linux.ibm.com> wrote:
>>>
>>> On Tue, Jul 07, 2020 at 02:26:08PM +0200, David Hildenbrand wrote:
>>>> On 07.07.20 14:13, Mike Rapoport wrote:
>>>>> On Tue, Jul 07, 2020 at 01:54:54PM +0200, Michal Hocko wrote:
>>>>>> On Tue 07-07-20 13:59:15, Jia He wrote:
>>>>>>> This exports memory_add_physaddr_to_nid() for module driver to use.
>>>>>>>
>>>>>>> memory_add_physaddr_to_nid() is a fallback option to get the nid in case
>>>>>>> NUMA_NO_NID is detected.
>>>>>>>
>>>>>>> Suggested-by: David Hildenbrand <david@redhat.com>
>>>>>>> Signed-off-by: Jia He <justin.he@arm.com>
>>>>>>> ---
>>>>>>>  arch/arm64/mm/numa.c | 5 +++--
>>>>>>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
>>>>>>> index aafcee3e3f7e..7eeb31740248 100644
>>>>>>> --- a/arch/arm64/mm/numa.c
>>>>>>> +++ b/arch/arm64/mm/numa.c
>>>>>>> @@ -464,10 +464,11 @@ void __init arm64_numa_init(void)
>>>>>>>
>>>>>>>  /*
>>>>>>>   * We hope that we will be hotplugging memory on nodes we already know about,
>>>>>>> - * such that acpi_get_node() succeeds and we never fall back to this...
>>>>>>> + * such that acpi_get_node() succeeds. But when SRAT is not present, the node
>>>>>>> + * id may be probed as NUMA_NO_NODE by acpi, Here provide a fallback option.
>>>>>>>   */
>>>>>>>  int memory_add_physaddr_to_nid(u64 addr)
>>>>>>>  {
>>>>>>> - pr_warn("Unknown node for memory at 0x%llx, assuming node 0\n", addr);
>>>>>>>   return 0;
>>>>>>>  }
>>>>>>> +EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
>>>>>>
>>>>>> Does it make sense to export a noop function? Wouldn't make more sense
>>>>>> to simply make it static inline somewhere in a header? I haven't checked
>>>>>> whether there is an easy way to do that sanely bu this just hit my eyes.
>>>>>
>>>>> We'll need to either add a CONFIG_ option or arch specific callback to
>>>>> make both non-empty (x86, powerpc, ia64) and empty (arm64, sh)
>>>>> implementations coexist ...
>>>>
>>>> Note: I have a similar dummy (return 0) patch for s390x lying around here.
>>>
>>> Then we'll call it a tie - 3:3 ;-)
>>
>> So I'd be happy to jump on the train of people wanting to export the
>> ARM stub for this (and add a new ARM stub for phys_to_target_node()),
>> but Will did have a plausibly better idea that I have been meaning to
>> circle back to:
>>
>> http://lore.kernel.org/r/20200325111039.GA32109@willie-the-truck
>>
>> ...i.e. iterate over node data to do the lookup. This would seem to
>> work generically for multiple archs unless I am missing something?

IIRC, only memory assigned to/onlined to a ZONE is represented in the
pgdat node span. E.g., not offline memory blocks.

Esp., when hotplugging + onlining consecutive memory, there won't really
be any intersections in most cases if I am not wrong. It would not be
"intersection" but rather "closest fit".

With overlapping nodes it's even more unclear. Which one to pick?

> 
> I think it would work on arm64, power and, most propbably on s390

With only a single dummy node I guess it should work (searching when
there is only a single node does not make too much sense).

> (David?), but not on x86. x86 does not have reserved memory in pgdat,
> it's never memblock_add()'ed (see e820__memblock_setup()).

Can you enlighten me why that is relevant for the memory hotplug path?
(or is it just a general comment to make the function as accurate as
possible for all addresses?)

-- 
Thanks,

David / dhildenb