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(p200300cbc71c360033e6971c5f64fab5.dip0.t-ipconnect.de. [2003:cb:c71c:3600:33e6:971c:5f64:fab5]) by smtp.gmail.com with ESMTPSA id m40-20020a05600c3b2800b004042dbb8925sm6330795wms.38.2023.11.30.08.54.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 30 Nov 2023 08:54:27 -0800 (PST) Message-ID: Date: Thu, 30 Nov 2023 17:54:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 03/70] RAMBlock/guest_memfd: Enable KVM_GUEST_MEMFD_ALLOW_HUGEPAGE Content-Language: en-US To: Sean Christopherson Cc: Xiaoyao Li , Paolo Bonzini , Igor Mammedov , "Michael S . Tsirkin" , Marcel Apfelbaum , Richard Henderson , Peter Xu , =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , Cornelia Huck , =?UTF-8?Q?Daniel_P_=2E_Berrang=C3=A9?= , Eric Blake , Markus Armbruster , Marcelo Tosatti , qemu-devel@nongnu.org, kvm@vger.kernel.org, Michael Roth , Claudio Fontana , Gerd Hoffmann , Isaku Yamahata , Chenyi Qiang References: <20231115071519.2864957-1-xiaoyao.li@intel.com> <20231115071519.2864957-4-xiaoyao.li@intel.com> <05f0e440-36a2-4d3a-8caa-842b34e50dce@intel.com> <0fbfc413-7c74-4b2a-bade-6f3f04ca82c2@redhat.com> <4708c33a-bb8d-484e-ac7b-b7e8d3ed445a@intel.com> <45d28654-9565-46df-81b9-6563a4aef78c@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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 30.11.23 17:01, Sean Christopherson wrote: > On Thu, Nov 30, 2023, David Hildenbrand wrote: >> On 30.11.23 08:32, Xiaoyao Li wrote: >>> On 11/20/2023 5:26 PM, David Hildenbrand wrote: >>>> >>>>>> ... did you shamelessly copy that from hw/virtio/virtio-mem.c ? ;) >>>>> >>>>> Get caught. >>>>> >>>>>> This should be factored out into a common helper. >>>>> >>>>> Sure, will do it in next version. >>>> >>>> Factor it out in a separate patch. Then, this patch is get small that >>>> you can just squash it into #2. >>>> >>>> And my comment regarding "flags = 0" to patch #2 does no longer apply :) >>>> >>> >>> I see. >>> >>> But it depends on if KVM_GUEST_MEMFD_ALLOW_HUGEPAGE will appear together >>> with initial guest memfd in linux (hopefully 6.8) >>> https://lore.kernel.org/all/CABgObfa=DH7FySBviF63OS9sVog_wt-AqYgtUAGKqnY5Bizivw@mail.gmail.com/ >>> >> >> Doesn't seem to be in -next if I am looking at the right tree: >> >> https://git.kernel.org/pub/scm/virt/kvm/kvm.git/log/?h=next > > Yeah, we punted on adding hugepage support for the initial guest_memfd merge so > as not to rush in kludgy uABI. The internal KVM code isn't problematic, we just > haven't figured out exactly what the ABI should look like, e.g. should hugepages > be dependent on THP being enabled, and if not, how does userspace discover the > supported hugepage sizes? Are we talking about THP or hugetlb? They are two different things, and "KVM_GUEST_MEMFD_ALLOW_HUGEPAGE" doesn't make it clearer what we are talking about. This patch here "get_thp_size()" indicates that we care about THP, not hugetlb. THP lives in: /sys/kernel/mm/transparent_hugepage/ and hugetlb in: /sys/kernel/mm/hugepages/ THP for shmem+anon currently really only supports PMD-sized THP, that size can be observed via: /sys/kernel/mm/transparent_hugepage/hpage_pmd_size hugetlb sizes can be detected simply by looking at the folders inside /sys/kernel/mm/hugepages/. "tools/testing/selftests/mm/vm_util.c" in the kernel has a function "detect_hugetlb_page_sizes()" that uses that interface to detect the sizes. But likely we want THP support here. Because for hugetlb, one would actually have to instruct the kernel which size to use, like we do for memfd with hugetlb. Anon support for smaller sizes than PMDs is in the works, and once upstream, it can then be detected via /sys/kernel/mm/transparent_hugepage/ as well. shmem support for smaller sizes is partially in the works: only on the write() path. Likely, we'll make it configurable/observable in /sys/kernel/mm/transparent_hugepage/ as well. So if we are talking about THP for shmem, there really only is /sys/kernel/mm/transparent_hugepage/hpage_pmd_size. -- Cheers, David / dhildenb