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U2FsdGVkX1/brDPwslyoZA5pvS4Gm1KvjpyLHQLAdmnuMj5HCk4sNXNDZMdZ+pGgSyWcgrEx+vxZwN2Yt7eA7HUlyP83FeJAzWqa4+phLYGuufEmG0YqPyaqd4dAP5FwqYgdCr7Alt6b12zqdiz/OCX9vbODAE633DsDy9E3/MBT+tMirr6pTz4KgE0FfPQQSLsTQqkfpHzmxGrIhfrEoEkPoYmndylwDAb2Ws3UlNd9t5W0LLWhSp0EqdP6ZlE9pL2tGG6xiHpJ2w5vjA9tsmD619LAQylY1c/QEcHZT4Auu1oXVDd9FjiI3FMz3rhmo5j8UHzTT6s2QJ7duJC+d1946LVo57LrV0LBVu2V4Jgx9wktXGMOcBhxiK8GHVc02S6auCUgm+akoMQs6qWkJnkh555iI28U/BEf/YpwZ9KXfp93+adqLQ9y7NAIm6wGHSRe/47zInuTDs8nlZuI03HA9YeAK5oVqY7ZIyh9ulB6ZjeHDS6nzN9H6pSkEqUrrYjlw28YTANW5vFnxnowG3s6zWR53wd6gKxNDqyihk23AA0RkIcKmmBgWdu5rIEuoGN4QncJQ9b4Nn/HXHp9WQoXMVEsl0fMXiPJVZShBpiCzWcLiDgtls4KnJmhOMaFR7u0dRKApRaL1Ha6riHjcHAEiwgO/n+fqtAS72fwyXkcpXTHlWBm4l5fCoGUJt/jJokjrBOejWGob0xm3Lh5gDgMhrveWrnEA+qqEdc3tG3pO+uznTvJ1oOohST91BdvoG02fTsRzmYD+Kb3nusAS7h847jooEFusogYRlzgS1Xr0oHmDJfFba3XsXm9bB5rbBwbRMCooiZvrdtUXItSz17C6XxrOuIztDO9631GlsLUcV/mBzhwfVoxHTpq+RSguLRIUyz4exd9umo5o2sJHyQLO/5ZkcbIrYeeFxBtd7Do1SYyTLD2kmX18Yrdl1eY4m/fa+G+S8xRBmQojnb iR3+5Y3q baJRhY6eP0b0HYF0ZYACRFSYwc4VNulbQsAn6S+bFOboQeq9NV6GNN530X5A31LDMQ2yKzC29Zu9OrndUc9ZVOOAjRMVBeJo9Pa5U/W9V/b22loZnMKve+8Hov7r6/mVtL0OZ9aqxrgUicIGJ5ErrT/Ex0hAvNCgzL5adQm0qnKYFdFZr9XxOBGydYBSPdIThDqofrWjuvXEVPIJQXf2vkhjZMR1uI7klp5vo9WDafsd3mSp+fJW22ZLTUrkjFBrK/sMk34cBaJRttF8CGlJnPXTSFwNOyIU0xTfTPjyKPzInzHIPYO6TJHfWdNbItJbeF2XSH8lUcSwyKRND7/ySBhRoiU9zykMuuCWhmYdOWQCoT3XAbx8y1HBHmh//EY2CAJ9I7m4tQAh05pUYWJ3cV5rJYgYV3o92aJr//T+AeDKx0oSiAh43ArCQnQ== 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 Wed, Oct 22, 2025 at 12:10:35AM -0700, Christoph Hellwig wrote: > On Mon, Oct 20, 2025 at 09:58:54AM -0300, Jason Gunthorpe wrote: > > I explained it in detail in the message you are repling to. If > > something is not clear can you please be more specific?? > > > > Is it the mmap in VFIO perhaps that is causing these questions? > > > > VFIO uses a PFNMAP VMA, so you can't pin_user_page() it. It uses > > unmap_mapping_range() during its remove() path to get rid of the VMA > > PTEs. > > This all needs to g• into the explanation. > > > Instead the DMABUF FD is used to pass the MMIO pages between VFIO and > > another driver. DMABUF has a built in invalidation mechanism that VFIO > > triggers before remove(). The invalidation removes access from the > > other driver. > > > > This is different than NVMe which has no invalidation. NVMe does > > unmap_mapping_range() on the VMA and waits for all the short lived > > pgmap references to clear. We don't need anything like that because > > DMABUF invalidation is synchronous. > > Please add documentation for this model to the source tree. Okay, Lets see what we can come up with. I think explaining the dmabuf model with respect to the p2p provider in the new common dmabuf mapping API code would make sense. Jason