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[99.254.144.39]) by smtp.gmail.com with ESMTPSA id k28-20020a05620a143c00b0075785052e97sm2992025qkj.95.2023.06.26.12.04.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Jun 2023 12:04:23 -0700 (PDT) Date: Mon, 26 Jun 2023 15:04:21 -0400 From: Peter Xu To: Jason Gunthorpe Cc: David Hildenbrand , "Kasireddy, Vivek" , "dri-devel@lists.freedesktop.org" , "linux-mm@kvack.org" , Mike Kravetz , Gerd Hoffmann , "Kim, Dongwon" , Andrew Morton , James Houghton , Jerome Marchand , "Chang, Junxiao" , "Kirill A . Shutemov" , "Hocko, Michal" , Muchun Song , John Hubbard Subject: Re: [PATCH v1 0/2] udmabuf: Add back support for mapping hugetlb pages Message-ID: References: <20230622072710.3707315-1-vivek.kasireddy@intel.com> <6e429fbc-e0e6-53c0-c545-2e2cbbe757de@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Queue-Id: 870A5180010 X-Rspam-User: X-Stat-Signature: mnbbzoeqakizwjj5x7o9qrb71acqog3i X-Rspamd-Server: rspam01 X-HE-Tag: 1687806268-279671 X-HE-Meta: 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 8AsKDIZm WokcoORugar/ahWVvSAyD1L7UuuW90rbRwrbc9TafRj0QQXHvRaAJXvuVrgEJskztXV++FAQVqqCGkDTdUs+VnYzT7+429JcEc3l55FzElg5wjm4GMDzPqC80gEmoH7JzGoZ6t9k9MSr/ZvxHyLn4oVyEe9rBSV8xePgKqOCEnO7VQkrFSbvLOg7AD3esIM2VVNpAMD0Ng68iylJGc43psF9WTDCPV2iN80auXk40+BrmMwxCFAzPR5eh/njcVO1QR0aQ3TRsHGjp7VxU+Ezq3lYKEqJJ5ErDCSYPdsjLAudPhT8hK3ip8KoVNv0SJ14c6UhOCP5bqkFkwdeXY2FgKk0txtpkHDn/bY62Y1nWwcreBmmNo4c514QqZaLZGdI9xd5t/8iTJ2lD/oUxzzg4+WXlbOf9rK82n/9xUTrDpmBonReoiYPy2zhfJw== 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: On Mon, Jun 26, 2023 at 03:18:48PM -0300, Jason Gunthorpe wrote: > On Mon, Jun 26, 2023 at 08:14:27PM +0200, David Hildenbrand wrote: > > > So we might have to implement the same page migration as gup does on > > FOLL_LONGTERM here ... maybe there are more such cases/drivers that actually > > require that handling when simply taking pages out of the memfd, believing > > they can hold on to them forever. > > In general I would like to see an interface to FOLL_LONGTERM pin pages > from a memfd. I would quite happily use that in iommufd as well. > > It solves some problems we have there with fork/exec/etc if the pages > are not linked to a mm_struct. Afaiu any fd based approach should mean it'll never work with private memories, while mm-based should be able to work on any kind. Maybe that's not a problem - I assume at least udmabuf should just only work with shared memories; not sure on iommufd, though. -- Peter Xu