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[2003:cb:c736:ca00:b4c3:24bd:c2f5:863c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-438bd4d34e3sm134224415e9.39.2025.01.27.06.40.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Jan 2025 06:40:18 -0800 (PST) Message-ID: <9b0fa1f7-4133-4111-9142-143c36c42f8d@redhat.com> Date: Mon, 27 Jan 2025 15:40:17 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] kernel/resource: Introduce managed SOFT RESERVED resources To: "Fontenot, Nathan" , Fan Ni Cc: linux-cxl@vger.kernel.org, dan.j.williams@intel.com, alison.schofield@intel.com, linux-mm@kvack.org, gourry@gourry.net References: <1800b17449d1c231292c85f59b226aff39a81552.1737046620.git.nathan.fontenot@amd.com> <4e556200-c790-4e0a-b103-2a1529c81927@redhat.com> <3c7c5b87-f241-482b-9b00-98e2e53d8e9c@amd.com> <5067fda1-c2de-4a20-9025-ebdf90ebba8e@amd.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: <5067fda1-c2de-4a20-9025-ebdf90ebba8e@amd.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: e9giZk4OF2TFHkMw331Xxl8I2UpASwFZAUr0dUNNX4Y_1737988820 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: A58741C0014 X-Stat-Signature: mq7hixfjsarya436tqxau7m1n667hbdq X-HE-Tag: 1737988825-974105 X-HE-Meta: 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 Hdq+rcUR wd/4E8AeRtc0ouZDoAnZSCsuoOpa1YWAQI2rQp1ikDHnSCveMV86pWQDjAG7p9H+R24Apx5/FzYQj6xMsqQSHavSa/D3d1Sls7MEut0g+1AxXjPTi7pzPM1tTys2Dj+LZ7bFkzjJaYRD9ps0u8sInC49Z6jCyQEIezt+skJzs/lZilh9NDoqoK+5vKoAqvixmP/ozlwMRj9LctcjAFe60Dym34Trv4D4Hv0k/MfpyjwNCFvsemOVjiJ9P3V2kC7uo7j/3F45tbMTJuTDJ45e/z7w0E3PRq9G6pO6CDr9tRdKuMFiK7PBRFVZGqLccNtPM89YHVu4SiE6MHs9Q/EUTFuJbyVEgoOJQwx9Z49vibSdmF7ySQRbtAonzuY3kkdhx0aFcbTHwA2WsAsvCzdnbrYFRTNa/qq4DYPrh71Aluwg8oUS5fq9bJ5ipBcwCK631rGeOSL8wjDDNbJib43MGCoSfsoGkYOV0GDUM/VP4uBej5SY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000242, 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 23.01.25 16:49, Fontenot, Nathan wrote: > On 1/22/2025 12:03 AM, Fan Ni wrote: >> On Tue, Jan 21, 2025 at 12:57:19PM -0600, Fontenot, Nathan wrote: >>> >>> >>> On 1/21/2025 2:19 AM, David Hildenbrand wrote: >>>> On 16.01.25 18:42, Nathan Fontenot wrote: >>>> >>>> Hi, >>>> >>>>> Introduce the ability to manage SOFT RESERVED kernel resources prior to >>>>> these resources being  placed in the iomem resource tree. This provides >>>>> the ability for drivers to update SOFT RESERVED resources that intersect >>>>> with their memory resources. >>>>> >>>>> During boot, any resources marked as IORES_DESC_SOFT_RESERVED are placed >>>>> on the soft reserve resource tree. Once boot completes all resources >>>>> are placed on the iomem resource tree. This behavior is gated by a new >>>>> kernel option CONFIG_SOFT_RESERVED_MANAGED. >>>>> >>>> >>>> I'm missing a bit of context here. >>>> >>>> Why can't we flag these regions in the existing iomem tree, where they can be fixed up (even after boot?)? >>>> >>>> Especially, what about deferred driver loading after boot? Why is that not a concern or why can we reliably handle everything "during boot" ? >>> >>> That's a good question and one I should have addressed. >>> Sorry for the late reply. >>> The goal is to prevent the dax driver from creating dax devices for soft reserve >>> resources prior to the soft reserve resources being updated for any intersecting >>> cxl regions. >> >> Not an export. Can you explain a little more here? >> What is the problem if we only flag the resources as "soft >> reserved" in the iomem tree without creating a separate tree, and >> process the "soft reserved" resources only when needed? > > The issue we currently encounter is that the dax driver consumes these soft reserve > resources and creates dax devices for the soft reserve resources before the cxl driver > comnpletes device probe and can update the soft reserve resources to remove any > intersections with cxl regions. We do not want these soft reserves consumed prior > to them being updated. > > If we were to put the soft reserves on the iomem tree we would need to have the > cxl driver provide a notification that it has completed updates and others (i.e. dax) > can them go process the soft reserve resources. Would there be any blocker to that approach? Adding them all to the resource tree and flagging them as soft-reserved, to then have a signal that allows DAX to work on these, sounds cleaner to me. -- Cheers, David / dhildenb