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[34.168.217.79]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a88b3eec76sm159008945ad.19.2026.02.02.14.45.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Feb 2026 14:45:52 -0800 (PST) Date: Mon, 2 Feb 2026 22:45:48 +0000 From: David Matlack To: Samiullah Khawaja Cc: Jason Gunthorpe , David Woodhouse , Lu Baolu , Joerg Roedel , Will Deacon , Pasha Tatashin , iommu@lists.linux.dev, Robin Murphy , Pratyush Yadav , Kevin Tian , Alex Williamson , linux-kernel@vger.kernel.org, Saeed Mahameed , Adithya Jayachandran , Parav Pandit , Leon Romanovsky , William Tu , Vipin Sharma , YiFei Zhu , Chris Li , praan@google.com Subject: Re: [RFC PATCH v2 00/32] Add live update state preservation Message-ID: References: <20251202230303.1017519-1-skhawaja@google.com> <20260128195943.GY1641016@ziepe.ca> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On 2026-01-28 05:11 PM, Samiullah Khawaja wrote: > On Wed, Jan 28, 2026 at 11:59 AM Jason Gunthorpe wrote: > > On Tue, Dec 02, 2025 at 11:02:30PM +0000, Samiullah Khawaja wrote: > > Start off by just making the successor kernel fail to accept any > > drivers at all because the iommu_domain was preserved. ie restore the > > domain and set it as the default_domain and then fail in > > iommu_device_use_default_domain() and related functions. > > Right. In this model, the device would remain unusable after > liveupdate as you cannot do session finish. So the only way to recover > would be to do a proper reboot. But I think this is a great > intermediate step. This will break the new selftest vfio_pci_liveupdate_kexec_test that is added in the vfio cdev series: https://lore.kernel.org/kvm/20260129212510.967611-19-dmatlack@google.com/ https://lore.kernel.org/kvm/20260129212510.967611-23-dmatlack@google.com/ And having to reboot a machine back to life after every Live Update will be a painful for everyone working on VFIO, PCI, and IOMMU Live Update support. I agree with wanting to do incremental steps, but can we target that the intial iommufd series supports an e2e scenario that doesn't leave the host (or its devices) in an unusable state?