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Fri, 10 Jul 2026 14:26:23 -0700 (PDT) Date: Fri, 10 Jul 2026 21:26:03 +0000 Mime-Version: 1.0 X-Mailer: git-send-email 2.55.0.795.g602f6c329a-goog Message-ID: <20260710212616.1351130-1-dmatlack@google.com> Subject: [PATCH v7 00/12] PCI: liveupdate: PCI core support for Live Update From: David Matlack To: kexec@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org Cc: Adithya Jayachandran , Alexander Graf , Alex Williamson , Bjorn Helgaas , Chris Li , David Matlack , David Rientjes , Jacob Pan , Jason Gunthorpe , Jonathan Corbet , Josh Hilke , Leon Romanovsky , Lukas Wunner , Mike Rapoport , Parav Pandit , Pasha Tatashin , Pranjal Shrivastava , Pratyush Yadav , Saeed Mahameed , Samiullah Khawaja , Shuah Khan , Vipin Sharma , William Tu , Yi Liu Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260710_142625_181286_10AB4DE1 X-CRM114-Status: GOOD ( 19.05 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org This series can be found on GitHub: https://github.com/dmatlack/linux/tree/liveupdate/pci/base/v7 This series introduces initial support in the PCI core for Live Update, enabling drivers to preserve PCI devices across a kexec-based kernel update without interrupting the device. This functionality is critical for minimizing downtime in environments where PCI devices (e.g., those assigned to VMs via VFIO) must continue operating or maintain state across a host kernel upgrade. Specifically, this series allows preserved PCI devices to perform uninterrupted memory transactions (DMA) to/from system memory across a Live Update. These devices can be behind a bridge but must not be VFs. Support for P2P and VF preservation will be addressed in future series. Series Overview --------------- This series implements the following to support PCI device preservation across Live Update: 1. Set up a File-Lifecycle-Bound (FLB) handler to track and preserve PCI-specific state (struct pci_ser) across Live Update using Kexec Handover (KHO). 2. Add APIs for drivers to register devices for preservation (outgoing) and for the PCI core to identify preserved devices during enumeration (incoming) 3. Automatically preserve all upstream bridges for any preserved endpoint. Use reference counting to ensure bridges remain preserved as long as any downstream device is preserved. 4. Guarantee that preserved devices retain the same RequesterID (bus, device, function) for the duration of their preservation by inheriting secondary bus numbers, subordinate bus numbers, and ARI Forwarding Enable on preserved bridges. 5. Guarantee that memory transactions to/from preserved devices are routed consistently by inheriting Access Control Services (ACS) flags across a Live Update, from the endpoint up to the root port. 6. Modify the PCI shutdown path to avoid disabling bus mastering on preserved devices, thereby allowing preserved devices to perform uninterrupted during kexec for Live Update. 7. Provide comprehensive documentation for the FLB API, device tracking mechanisms, and the division of responsibilities between the PCI core, drivers, and userspace. Dependencies ------------ This series is built on top of the next branch of the liveupdate.git tree: https://git.kernel.org/pub/scm/linux/kernel/git/liveupdate/linux.git/log/?h=next Testing ------- This series was tested in conjunction with v4 of the VFIO PCI driver series: https://lore.kernel.org/kvm/20260511234802.2280368-1-vipinsh@google.com/ The full set of patches used for testing can be found on GitHub. Some conflict resolution was required to rebase VFIO v4 patchs on top of the 7.2-rc1 base. https://github.com/dmatlack/linux/tree/liveupdate/pci/base/v7-with-vfio Testing was performed using the new VFIO selftests: - vfio_pci_liveupdate_uapi_test - vfio_pci_liveupdate_kexec_test Both tests were run in a QEMU-based VM environment (using a single virtio-net PCIe device connected to a root port to exercise bridge support) and on bare metal using an Intel EMR server with 8x Intel DSA PCIe devices and 1x NVMe device. Future Work ----------- Following this series, we expect to make further improvements to the PCI core support for Live Update: - Allow P2P across Live Update by avoiding resizing or moving preserved device BARs and preserving all upstream bridge windows. - Support preserving Virtual Functions by preserving SR-IOV configuration on PFs and enumerating VFs after Live Update. Changelog --------- v7: - Use kho_block_set for dynamic device preservation, redefining ABI struct pci_ser to use a physical address instead of a fixed-size flexible array (Pasha Tatashin) - Add kernel-doc comments for pci_liveupdate_scan_bridge_begin() and pci_liveupdate_scan_bridge_end() (Pasha Tatashin) - Move refcount to patch 1 and adjust KHO ABI versioning progression accordingly (Pasha Tatashin) - Sphinx documentation improvements: add _luo and _flb labels and use acronyms with :ref: links (Pasha Tatashin) - Panic on failure to retrieve incoming PCI FLB data to avoid ongoing DMA from preserved devices causing memory corruption (Sashiko, Samiullah Khawaja) - Clarify comment about device-specific ACS quirks in incoming kernel (Pranjal Shrivastava) - Sort includes alphabetically in liveupdate.c (Pasha Tatashin) v6: https://lore.kernel.org/linux-pci/20260522202410.3104264-1-dmatlack@google.com/ v5: https://lore.kernel.org/linux-pci/20260512184846.119396-1-dmatlack@google.com/ v4: https://lore.kernel.org/linux-pci/20260423212316.3431746-1-dmatlack@google.com/ v3: https://lore.kernel.org/kvm/20260323235817.1960573-1-dmatlack@google.com/ v2: https://lore.kernel.org/kvm/20260129212510.967611-1-dmatlack@google.com/ v1: https://lore.kernel.org/kvm/20251126193608.2678510-1-dmatlack@google.com/ rfc: https://lore.kernel.org/kvm/20251018000713.677779-1-vipinsh@google.com/ David Matlack (12): PCI: liveupdate: Set up FLB handler for the PCI core PCI: liveupdate: Track outgoing preserved PCI devices PCI: liveupdate: Track incoming preserved PCI devices PCI: liveupdate: Document driver binding responsibilities PCI: liveupdate: Keep bus numbers constant during Live Update PCI: liveupdate: Auto-preserve upstream bridges across Live Update PCI: Refactor matching logic for pci_dev_acs_ops PCI: liveupdate: Inherit ACS flags in incoming preserved devices PCI: liveupdate: Inherit ARI Forwarding Enable on preserved bridges PCI: liveupdate: Freeze preservation status during shutdown PCI: liveupdate: Do not disable bus mastering on preserved devices during kexec Documentation: PCI: Add documentation for Live Update Documentation/PCI/index.rst | 1 + Documentation/PCI/liveupdate.rst | 29 + .../admin-guide/kernel-parameters.txt | 6 +- Documentation/core-api/liveupdate.rst | 5 + MAINTAINERS | 15 + drivers/pci/Kconfig | 15 + drivers/pci/Makefile | 1 + drivers/pci/liveupdate.c | 910 ++++++++++++++++++ drivers/pci/liveupdate.h | 68 ++ drivers/pci/pci-driver.c | 9 +- drivers/pci/pci.c | 14 +- drivers/pci/pci.h | 5 + drivers/pci/probe.c | 22 +- drivers/pci/quirks.c | 58 +- include/linux/kho/abi/pci.h | 59 ++ include/linux/pci.h | 4 + include/linux/pci_liveupdate.h | 77 ++ 17 files changed, 1260 insertions(+), 38 deletions(-) create mode 100644 Documentation/PCI/liveupdate.rst create mode 100644 drivers/pci/liveupdate.c create mode 100644 drivers/pci/liveupdate.h create mode 100644 include/linux/kho/abi/pci.h create mode 100644 include/linux/pci_liveupdate.h base-commit: 1354afac14579ad38279f12d660df961b5f20246 -- 2.55.0.795.g602f6c329a-goog