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Sat, 29 Nov 2025 19:13:14 -0800 (PST) Received: from [2a00:79e0:2eb0:8:7b08:e467:32c2:1b3e] ([2a00:79e0:2eb0:8:7b08:e467:32c2:1b3e]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7d1520a03a3sm9410054b3a.29.2025.11.29.19.13.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 29 Nov 2025 19:13:12 -0800 (PST) Date: Sat, 29 Nov 2025 19:13:11 -0800 (PST) From: David Rientjes To: Alexander Graf , Anthony Yznaga , David Hildenbrand , David Matlack , 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 November 17, 2025 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: 2506D40012 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: d6o5f1p3z4bb8x8s4z1bfq6optwzws8q X-HE-Tag: 1764472395-818506 X-HE-Meta: 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 0bhQ9NVk jYgvVNbJ1UHnapZvzcaGcEQUfLEboR3UpZZ7kgrAKBrv96deJUXCitHBx30oTydlNPcYF0KnY7nvuFo3Eku2HitC3nZ5wqURGnfCi5AV/ckOWKvm7b66cy5NVJoCYxU6FDXG1ZHfBfrTEsMy7Fc6t0hxwllBVKlRN3/ceRbEGVsqOIllcaG4+EnCKbNOXGzipYHItIeOniRGQ3LBcIzK1gO/v3AFVGnM+KzQuL/sJ3AZL5EOjL0S7W2+X422Jp4BMkOZN2k1gawHbeRmhXTHVRInDLel+nUU6RmVDbYUxyvGMNh9oLWHhsQiQAK5UjrK6bZfJvTKiyD9RLU1nsU1WNiB57jNB7j0nae2Nqw/fQYaJOhoptz8cLhJ7YRI+/1jwzMHgaYs/sKXVc1ThjajzyPbvf260/twS7mSNjoLn1BGMpHw= 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: Hi everybody, Here are the notes from the last Hypervisor Live Update call that happened on Monday, November 17. 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 the status of the stateless KHO RFC: Jason Miu had sent an update of the patches but they need to be rebased on top of the latest KHO series. There were some simplification patches that had been sent for KHO that changed how the FDT was used. Thus, the stateless KHO patches need to be updated again as well as some splitting of the patches into finer grained patches. LUO v6 was sent the previous weekend. There were a number of comments received for LUO v5 in linux-next that were addressed in v6. Mike Rapoport was going through v6 and provided the most feedback. Pasha was planning on sending a v7 for the next merge window. ----->o----- David Matlack updated that he was going to be focused this week on the VFIO v2 patch series. His goal was to have it on the mailing list by the week of November 24. The goal was to be able to gather feedback prior to LPC and then leverage that conference to discuss the open questions for that series. Sami and David had discussed a minimal patch series for VFIO preservation as the next feature that could be merged on top of LUO, setting the stage for IOMMU preservation to build on that. ----->o----- Pratyush updated on his HugeTLB and 1GB page preservation series, he got this working internally for v5. It is not ready to post as an RFC yet, so the goal was to have this in a state ready to share over the next two weeks. This will also enable LPC discussions. ----->o----- Ackerley provided an update on guest memfd support for 1GB HugeTLB pages. He has an internal version working. There is no preservation support for it, just guest memfd with 1GB HugeTLB support. Pratyush had previously discussed with Ackerley and felt that the series were really independent from each other. Ackerley was planning his next posting to the mailing list after LPC. ----->o----- Pratyush discussed an idea about versioning for LUO: there will be different versions for different components like memfd, IOMMU, etc. He was thinking to have a mechanism to define different versions. This would be supported as an ELF header in the vmlinux. When you load the next kernel in preparation for kexec, luod would read this next vmlinux, see what version it supports and determine its compatibility with the currently running kernel. Jason suggested discussing the roadmap for FDT first, he wanted to ensure that the dependencies were sorted out fully before doing optimization. He wanted to see more infrastructure to support the versioning and wrote some thoughts on this on the mailing list previously. The ELF versioning could just auto-generate out of the aligned design. Pratyush proposed writing an RFC that could be used as the basis for further discussion. ----->o----- Next meeting will be on Monday, December 1 at 8am PST (UTC-8), everybody is welcome: https://meet.google.com/rjn-dmzu-hgq Topics for the next meeting: - update on the status of stateless KHO RFC patches that were being rebased on top of the KHO simplification - update on the the status of LUO v7 and its potential for merge in the next merge window - update for the VFIO v2 patch series intended to solicit feedback prior to LPC - next steps for iommu persistence to build upon the VFIO patch series once that is merged - status update for HugeTLB + 1GB page preservation support that should be ready to send out by the next meeting - continued discussion on versioning support for various components for luod to negotiate - determine plan for December 15 instance of the meeting since it's immediately after LPC - later, after LPC: update on status of guest_memfd support for 1GB HugeTLB pages - later: testing methodology to allow downstream consumers to qualify that live update works from one version to another - later: reducing blackout window during live update, including deferred struct page initialization Please let me know if you'd like to propose additional topics for discussion, thank you!