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(p200300cbc748ba001c0048ea7b5ac12b.dip0.t-ipconnect.de. [2003:cb:c748:ba00:1c00:48ea:7b5a:c12b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42182ed2b23sm75337235e9.18.2024.06.11.01.04.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Jun 2024 01:04:17 -0700 (PDT) Message-ID: <30b5d493-b7c2-4e63-86c1-dcc73d21dc15@redhat.com> Date: Tue, 11 Jun 2024 10:04:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 2/3] mm/memory_hotplug: initialize memmap of !ZONE_DEVICE with PageOffline() instead of PageReserved() To: Oscar Salvador Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev, xen-devel@lists.xenproject.org, kasan-dev@googlegroups.com, Andrew Morton , Mike Rapoport , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Alexander Potapenko , Marco Elver , Dmitry Vyukov References: <20240607090939.89524-1-david@redhat.com> <20240607090939.89524-3-david@redhat.com> <5d9583e1-3374-437d-8eea-6ab1e1400a30@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz 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+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: B557D1C0024 X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: eekmjss4yjr5gk8c6opr73ub45ryr6q5 X-HE-Tag: 1718093067-910238 X-HE-Meta: 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 kqkP+Czx 8Wo+clYWOxRKaB+lAg4rWXHb4H3Ct6a1ntueEPeZxFcgKgXuq3xyBcTS0o0iuVsZyF1YvVwYr1NHF2yhjS15xLwUPW4A/BcWxEPzywxBlhO0yf3b7LnltTm05w5/+z6WBWnP7s5BvpcJeGtkMpGn+4g8zba80tqeep5fqb0EoQN8KvJ17Zs0ozUI/SLfr0ooA0cTAbgxCFLzyA5GK/3e11vAbr9KC9GAcTXeXFqCwlguv1F8YAkYA4408O+VPglAwwJSYps5QGdTnq+LTazrY3LXEmx9CSk96PocWwswnee2NSsVBvIZNlhOcqrQk1Pi1F5cxmh+QSxl2QdXUmcaQdWi+mKxUF2JproDreqcfwHqZneotaasBcXkblxO92I+pug41v1cFJ7VvaDimhdH7hyRx1YWqgjbkGg3B X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11.06.24 09:45, Oscar Salvador wrote: > On Mon, Jun 10, 2024 at 10:56:02AM +0200, David Hildenbrand wrote: >> There are fortunately not that many left. >> >> I'd even say marking them (vmemmap) reserved is more wrong than right: note >> that ordinary vmemmap pages after memory hotplug are not reserved! Only >> bootmem should be reserved. > > Ok, that is a very good point that I missed. > I thought that hotplugged-vmemmap pages (not selfhosted) were marked as > Reserved, that is why I thought this would be inconsistent. > But then, if that is the case, I think we are safe as kernel can already > encounter vmemmap pages that are not reserved and it deals with them > somehow. > >> Let's take at the relevant core-mm ones (arch stuff is mostly just for MMIO >> remapping) >> > ... >> Any PageReserved user that I am missing, or why we should handle these >> vmemmap pages differently than the ones allocated during ordinary memory >> hotplug? > > No, I cannot think of a reason why normal vmemmap pages should behave > different than self-hosted. > > I was also confused because I thought that after this change > pfn_to_online_page() would be different for self-hosted vmemmap pages, > because I thought that somehow we relied on PageOffline(), but it is not > the case. Fortunately not :) PageFakeOffline() or PageLogicallyOffline() might be clearer, but I don't quite like these names. If you have a good idea, please let me know. > >> In the future, we might want to consider using a dedicated page type for >> them, so we can stop using a bit that doesn't allow to reliably identify >> them. (we should mark all vmemmap with that type then) > > Yes, a all-vmemmap pages type would be a good thing, so we do not have > to special case. > > Just one last thing. > Now self-hosted vmemmap pages will have the PageOffline cleared, and that > will still remain after the memory-block they belong to has gone > offline, which is ok because those vmemmap pages lay around until the > chunk of memory gets removed. Yes, and that memmap might even get poisoned in debug kernels to catch any wrong access. > > Ok, just wanted to convince myself that there will no be surprises. > > Thanks David for claryfing. Thanks for the review and raising that. I'll add more details to the patch description! -- Cheers, David / dhildenb