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Peter Anvin" , Jonathan Corbet , Shuah Khan Cc: David Woodhouse , Ackerley Tng , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Steffen Eiden , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvmarm@lists.linux.dev, iommu@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [RFC PATCH 0/9] mm: Memory providers for guest_memfd and iommufd In-Reply-To: <20261006183235.16576-1-griffoul@gmail.com> References: <20260720111259.122911-1-dwmw2@infradead.org> <20261006183235.16576-1-griffoul@gmail.com> Date: Sat, 10 Oct 2026 13:06:09 +0530 Message-ID: MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: D1941180005 X-Rspam-User: X-Stat-Signature: tpdrdc1rs6og3nuz1ijb9bmae9ztpoig X-HE-Tag: 1791617788-927106 X-HE-Meta: U2FsdGVkX1+0n2C8jJsqSeFRmQx1GwPBVaQRq4EjvKlfdGYx10cGrjHGWkzR5Xw5Ua2StTIr2xCbg0cRU7UFmaUH51coQDwyR+eKWDbftkLRv58XQmJY9Gj+OReZi8ie02Gybs0yBrIi8VBuHZq2eYnovHCi1HBcIoS98IVm0VbHfO2YA3V9BcJIO1oPHnlYYTTDqPE37b6Pd+PzdVMdV2Xl/iOJQzOM/6Ye4hIhLyZPJJk3FXMj/FeVwEgPCIImi9hDeKJvvnJN0pIj65K5QsPk7WvZ1Y6hRs/XDq6Z0Pq/o9eegHHWSfXPWpo7bKqQCPN4CQ0YXnEV+ds6++XRbYT7TU9rPQKyYGw4di/xC6J+W79X6J+83lEOpWjBlGtc0IXkIMVDjfOgUDC7hY90a8LKfPZKxO+EnzB3koCz8EEU2HzBW8GniG8LJX9i1KYYHuAAHcZZLoJYYtmMCGuyxUgBoRLoSzvOmEpwGlCrAbgGxMAYamSW/yvgGmH3OPfh0x010C7kzYM4fAjcqR7u07O/o6FQwZDky3ALlVTbpX69m/LM6+6iwJXzjsaJZC6ZHjR9vLmA3inqUqW06n1xgsCBsJ2u7QJSlLdKAKvS8VxBLYTISWC06NqmbsH89Ed/GIVGLNwHudUayDbnZTSJpu7L0AG2ZqYpkIcKFVilMEpt1MZh2XE0joBTJKxF/jaxUuR1C/9aHWod3dXLTLHEvsojtbp7k5J5Rw+ciR45fO1foLiLhbk4/MOUxWxhSPK8D2UWfTP6U7bkMjhi8ohP738eNwyEPwLCrLFWQgRWAjb/nCaPCdUoNqPYbGqHD6Pdh4ivnoWrVumxCaWJzxJgv6aGHm25mLizvr3jrSjp4wKRPGt5VrcVcpIyA1ZK27sQBifbGZ8Rq37G0riraWv9GJgnYioMXlLixaRYOp53YyoPhU6k5NkwThGoULRsukezvCyIR56eOYPTVOW10Zt L6EyqQaM zlT8hyZQebu3aFE4aCWFEZUaKP08aST5JGK8c5HYsz6RBjjwY0FgYhSsztq0lx0+6uJ1Y4tm5AjkKroCwNJZDvgKY//PLcjljp2zjt3qquBiLv267+z4Z6FeZ9diUPrDStQMwmEgmJVXAVS99LWBeAV1LUPEVT4guLShmc/zVAMyi9YuZFtdL9s4n5pP9oI9USeQ694W90QTAg6IGo6vLbL3atCRCDZENfQWJjs3I89PZResAJgQfkt67a4IFVCmf/enUmMHLZ+YljX2D4DSZvEGe+M1qdYLhetb3H9uOt6PKxgCa8FW7jwmxZc8mpBxTSokUJ4/YI6xoHVtUvcHYTu3xsAVAX7WoxAJiU4eINh3yC8lR00526XQ8Xvq3UIenCP0k1UfsPMhr5Qk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Fred Griffoul writes: > From: Fred Griffoul > > Some drivers manage RAM outside the page allocator: a carve-out, device > memory, or memory that a host component moves between VMs while they > run. This memory often has no struct page. The driver wants to lend > pages to a VM and to its devices, and to take any of them back later. > > David Woodhouse's series "KVM: Allow alternative providers of > guest_memfd backed by PFNMAP memory" lets such a driver back a > guest_memfd through struct kvm_gmem_ops: > > https://lore.kernel.org/kvm/20260720111259.122911-1-dwmw2@infradead.org/ > > That covers the guest, but not the VM's devices, which his cover > letter left as an open question. This series adds a small interface in > mm: the driver that owns the memory becomes a provider, and the code > that maps it attaches as a consumer. There are two consumers, a > guest_memfd backend and IOMMU_IOAS_MAP_FILE in iommufd. > > The series is on top of David's v2 (base 0e35b9b6ec0f). Patch 1 was > part of the earlier dma-buf RFC. The provider backend depends on it, so > this series carries it. > I have been working on something similar for confidential computing use cases. There is likely some overlap between this series and what I posted at [1]. I have not reviewed this series in detail yet, but I will compare the two approaches and identify what can be shared between the use cases. Please let me know how you would like to proceed. [1] https://lore.kernel.org/all/20261010072504.536230-1-aneesh.kumar@kernel.org/ -aneesh