From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5BD3D3B95F9 for ; Fri, 10 Jul 2026 21:26:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783718788; cv=none; b=D1qs5/9hpmkgYXLAcEg840Zr4aw0KrmoVoRfrULOpzUK6fppW5UIyKmfMKnNHXYBNvSWmyonIYjK7BtW7TabNr3ty/1PMsVxqCOmv/ywYy7g39N5b/O5XaOYbZ39r8mm+v2g+ri2JLiqWfdhm1SrjZSHmdUQBj0dpGoavd5WHoc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783718788; c=relaxed/simple; bh=1aHgjBy7B5CxJBu4ZKVWz0/EFWhYHP/gU/x++i2l4Gs=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=NjWUpeS033kiqvdTRVqTFVDvrkMwNgikpTXxMfTlCb7ZHfV4XXa+m0EmEggvbvwFSRZqpRwir/5C85PxCXddhb3xXIaZ+odkrn+35D4i6vGnsb6nXScrs+Gc/0nFXRSHGdJuVb/r3L38RzKyXK0vPYwUSebuarFKQiF/UMna0r4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--dmatlack.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=hZ38aPit; arc=none smtp.client-ip=209.85.210.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--dmatlack.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="hZ38aPit" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-8484ba00601so1449657b3a.1 for ; Fri, 10 Jul 2026 14:26:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1783718783; x=1784323583; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:mime-version:date:from :to:cc:subject:date:message-id:reply-to:content-type; bh=he4LlVclK6dw2y5zUcgVn+6YxGRxdITg+d/Le4uVaLE=; b=hZ38aPitmeqOJBbteG1aSNiMhcbmq/k0vyRSNG/G4qkMw59dBeTru1NizEu0G0zByh FNi43/mDatKbD6gwKzujOntTpIusDwk/wdzn2WHTVeG+/6H0yZKRC66zi04CiBi3wWmH eFRVUdRD4YNT15RTwlzClekqnWv8gNvQ6cnp+3XSv+xuWfoA3i/lUCS70w/KK4mrBxxq HbDtaE8iKiGSe1OP1tzzhyqUprrQTt1CaDrsR6dKWQerEIDEDavADPIJt1RDCckW4puP 2LCAE+Ym7Os80N74iKRy9DWd5TfDGvelUx8+Q0zDOK6r2JWREstJI/uz9p0SkT4yIWi+ aBJg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783718783; x=1784323583; h=content-type:cc:to:from:subject:message-id:mime-version:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=he4LlVclK6dw2y5zUcgVn+6YxGRxdITg+d/Le4uVaLE=; b=LWe8CcAN9U4iWdxyydGaAEzOhHDKvS+DxJcZ7on7m47wJiHDYX5okq19AMeZ+pc1Dj TlCtkORIF6hsTAyBWUssQTK7MuHHl+CBEyiwx0j6C3X+UAxttjjt8vidus5zGqHzxTWc S57Q/5+bVQqgnZ4a/JFpd079qi3hPa6WIm2frHmnTEwqxZ1yb7/CO+AkQg7iulao5YMq bumcq2z3G4Xbqn2YkuzJjA0oAXh+auQqHar9mpcQkviuJys1XMkQmchD2G5aMYvxG5Ic VphnkCyNpBfm2QFeWqz7i7qDVYYXllefpEiBmlBXW8TC7kjy0/ntDrn8CHzuzw4JTsmF nY/w== X-Forwarded-Encrypted: i=1; AHgh+Rrcy+GDiCfKFXvkTCg82SJveu3D4q0Z5pdSHzVTUJaBj52WzqCSc5pyj2HpGot9uf1W9hrXApZbqXgvA1k=@vger.kernel.org X-Gm-Message-State: AOJu0YzF3Q5Ijhz5fss2Mt33WtLO7zIExJncVuop8VIGDrnTvTQ3Ue1f On4XS4ao2nDwMowqFB5U7D2a1clN6LHkRrL3kI16Mbk3SOVLk4G4XZMkOlMM4H0dogHgOb1VoZR C8SCpnA9k6MgKsA== X-Received: from pfud15.prod.google.com ([2002:a05:6a00:10cf:b0:847:9be8:84d5]) (user=dmatlack job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:228e:b0:82c:e9cc:f61d with SMTP id d2e1a72fcca58-848896c39e2mr550236b3a.9.1783718783127; Fri, 10 Jul 2026 14:26:23 -0700 (PDT) Date: Fri, 10 Jul 2026 21:26:03 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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" 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