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[2003:cb:c73f:8500:f83c:3602:5300:88af]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-36bbd06fbfdsm12912183f8f.106.2024.08.06.06.51.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 06 Aug 2024 06:51:23 -0700 (PDT) Message-ID: <4cdd93ba-9019-4c12-a0e6-07b430980278@redhat.com> Date: Tue, 6 Aug 2024 15:51:22 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 4/4] mm: guest_memfd: Add ability for mmap'ing pages To: Elliot Berman , Andrew Morton , Paolo Bonzini , Sean Christopherson , Fuad Tabba , Patrick Roy , qperret@google.com, Ackerley Tng Cc: linux-coco@lists.linux.dev, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org References: <20240805-guest-memfd-lib-v1-0-e5a29a4ff5d7@quicinc.com> <20240805-guest-memfd-lib-v1-4-e5a29a4ff5d7@quicinc.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: <20240805-guest-memfd-lib-v1-4-e5a29a4ff5d7@quicinc.com> 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: 4EAC040018 X-Stat-Signature: wpprn894iricggpwkqayze5achdauaoo X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1722952288-171594 X-HE-Meta: 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 9Q1ghmi0 zBqbAnK5WIpTpUUZts8/aPGOSZ/qYIa2edeiACO/wpHl6xzy1P9CitumHNXu3gySRHVilxUXWYanb6bX38Vs/oFPUGqmrBsHMq+Rex8uujddvxIvDFkYnhIQA35iBNuczIReUAbZA/d25JMYB18raA5ALf7Wquy5mptvNecNNO00idqcgXC7lyqe7wCD1zV8iDwTGVFYGD9FUk91y93vc1BR4+EcUtV5ogUTPELBk8OiFvc+Yd5m80H53BsUI+QNlV4Get4rcsbHIdOn73Yrmtlxjdt46cZ/Bvlw1FbXZIIWcceMacw7asAQukhi3b53biuTfi8lFeSJ68rnjH//Mu89dY+BvgHQwJ8z1dQv80sfbI5KBEU4nYGfpRfX5SYr3/w7FOTVRS5YiAQqg1w7I/S4hanxMiVIg0UG4+6j4aqA+RsI= 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: > > - if (gmem_flags & GUEST_MEMFD_FLAG_NO_DIRECT_MAP) { > + if (!ops->accessible && (gmem_flags & GUEST_MEMFD_FLAG_NO_DIRECT_MAP)) { > r = guest_memfd_folio_private(folio); > if (r) > goto out_err; > @@ -107,6 +109,82 @@ struct folio *guest_memfd_grab_folio(struct file *file, pgoff_t index, u32 flags > } > EXPORT_SYMBOL_GPL(guest_memfd_grab_folio); > > +int guest_memfd_make_inaccessible(struct file *file, struct folio *folio) > +{ > + unsigned long gmem_flags = (unsigned long)file->private_data; > + unsigned long i; > + int r; > + > + unmap_mapping_folio(folio); > + > + /** > + * We can't use the refcount. It might be elevated due to > + * guest/vcpu trying to access same folio as another vcpu > + * or because userspace is trying to access folio for same reason As discussed, that's insufficient. We really have to drive the refcount to 1 -- the single reference we expect. What is the exact problem you are running into here? Who can just grab a reference and maybe do nasty things with it? -- Cheers, David / dhildenb