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Fri, 24 Apr 2026 20:07:53 -0700 (PDT) Received: from [2a00:79e0:2eb0:8:a18f:54fc:a476:f72a] ([2a00:79e0:2eb0:8:a18f:54fc:a476:f72a]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3614186adddsm25961188a91.2.2026.04.24.20.07.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Apr 2026 20:07:52 -0700 (PDT) Date: Fri, 24 Apr 2026 20:07:51 -0700 (PDT) From: David Rientjes To: Alexander Graf , "Andersen, Tycho" , Anthony Yznaga , Baolu Lu , David Hildenbrand , David Matlack , "Heyne, Maximillian" , James Gowans , Jason Gunthorpe , Mike Rapoport , Pankaj Gupta , Pasha Tatashin , Pratyush Yadav , Praveen Kumar , Vipin Sharma , Vishal Annapurve , "Woodhouse, David" cc: linux-mm@kvack.org, kexec@lists.infradead.org Subject: [Hypervisor Live Update] Notes from April 20, 2026 Message-ID: <014fae14-28e1-ff32-c126-28bdffdff636@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Queue-Id: A45F5A0006 X-Rspamd-Server: rspam06 X-Stat-Signature: 6ifg9ym9smh5eafso8isbptk6hsdsd8f X-HE-Tag: 1777086475-847714 X-HE-Meta: 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 0S3qV5Vi 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi everybody, Here are the notes from the last Hypervisor Live Update call that happened on Monday, April 20. Thanks to everybody who was involved! These notes are intended to bring people up to speed who could not attend the call as well as keep the conversation going in between meetings. ----->o----- Pasha updated on systemd integration for LUO. He created a pull request for initial LUO support and that patch series is under review. In addition, the session limit was removed. Luca sent a patch series that allows finding the name for a session and logic to determine if this is a LUO session. Those patches are also under review. He also mentioned that Pratyush was working on boot time optimizations for KHO but were not in attendance at the meeting. Deferred struct page initialization v8 was sent out last Friday and all major comments have been addressed so we are hopeful these patches will be staged soon. For memblock improvements to automatically expand the scratch area, Pratyush is working on this and he'll likely send this series out soon. This will add a new data structure to find holes of 1GB or better to create separate radix tree for boot time allocations. ----->o----- David Matlack updated on VFIO and the roadmap going forward. He said that the series will be split into two with him taking the PCI core changes and iterate on those separately while Vipin Sharma takes the VFIO patches and selftests. While iterating on them independently, they will be tested together. v4 of the PCI core changes are prepped and ready but he's still cleaning them up for posting this week. Vipin updated on VFIO which will largely be based on the previous v3 patches and he is targeting sending these out before the next meeting. ----->o----- Samiullah updated on IOMMU persistence and said that it should be out by the end of this week for feedback. There was discussion upstream to preserve the minimum that is required to free the domain. He is planning on sharing a roadmap externally on the shared drive for discussion to keep the conversation going and to preview future thoughts. ----->o----- Maximilian Heyne joined us and noted that he is continuing Pratyush's work. Imagining a database or a process with a huge amount of cache or memory, all that memory is gone after updating to a new kernel. He wished to discuss how to preserve that memory over reboot or kexec. His idea is to take a process and dump its state to disk and then restore on the other side of the reboot. The problem is this takes a very long time so perhaps it would possible to leverage KHO to preserve the data in memfds. He is using splice to move pages from the process into the memfd and this seems very inefficient. He would like a solution where he can turn the process address space into a memfd to do the preservation directly. Pasha noted the limitation with CRIU was the snapshotting and restore that would make this difficult to do in place. He also pointed out existing APIs for preserving memory through DAX. He didn't think this would need to be an application level change but rather a CRIU snapshotting change. Pasha said the VM use case is different than CRIU because the guest memory is preserved but the data structures associated with it get recreated. Jason suggested the pathway would be equivalent to converting an anonymous VMA into a memfd so that CRIU can just use the memfd right away and that would likely be better as an upstream discussion including core MM developers. He thought that some amount of application enlightenment should be used for this, however, either through memfd or hugetlb. Pasha said an alternative may be to preserve random files in tmpfs. ----->o----- NOTE!!! The next meeting will be canceled due to LSF/MM/BPF 2026. Next meeting will be on Monday, May 18 at 8am PDT (UTC-7), everybody is welcome: https://meet.google.com/rjn-dmzu-hgq Topics for the next meeting: - systemd integration for LUO, patches from both Pasha and Luca - KHO optimizations for boot time performance including initialization of memblock list and deferred struct page initialization - HugeTLB preservation support including selftests and fallback allocation strategy - PCI core changes v4 and next round of VFIO patches including selftests - Vipin and David Matlack roadmap for PCI and VFIO changes to solicit upstream feedback - IOMMU persistence patch series status - Samiullah's roadmap for IOMMU persistence to share with stakeholders - Maximilian demo for persisting process memory across kexec - guest_memfd HugeTLB enlightenment: conversion support, HugeTLB support without restructuring, and HugeTLB support with restructuring - KHO support for Confidential VMs including page table preservation and pinning - later: versioning support for luod to negotiate - later: KHO enlightenment for ASI Please let me know if you'd like to propose additional topics for discussion, thank you!