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[34.83.236.195]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-834daf7f43bsm3432664b3a.58.2026.04.28.10.35.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Apr 2026 10:35:56 -0700 (PDT) Date: Tue, 28 Apr 2026 17:35:52 +0000 From: Samiullah Khawaja To: David Matlack Cc: iommu@lists.linux.dev, kexec@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, Adithya Jayachandran , Alexander Graf , Alex Williamson , Bjorn Helgaas , Chris Li , David Rientjes , Jacob Pan , Jason Gunthorpe , Joerg Roedel , Jonathan Corbet , Josh Hilke , Leon Romanovsky , Lukas Wunner , Mike Rapoport , Parav Pandit , Pasha Tatashin , Pranjal Shrivastava , Pratyush Yadav , Robin Murphy , Saeed Mahameed , Shuah Khan , Will Deacon , William Tu , Yi Liu Subject: Re: [PATCH v4 02/11] PCI: liveupdate: Track outgoing preserved PCI devices Message-ID: References: <20260423212316.3431746-1-dmatlack@google.com> <20260423212316.3431746-3-dmatlack@google.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: On Tue, Apr 28, 2026 at 05:24:53PM +0000, Samiullah Khawaja wrote: >On Thu, Apr 23, 2026 at 09:23:06PM +0000, David Matlack wrote: >>Add APIs to allow drivers to notify the PCI core of which devices are >>being preserved across a Live Update for the next kernel, i.e. >>"outgoing" devices. >> >>Drivers must notify the PCI core when devices are preserved so that the >>PCI core can update its FLB data (struct pci_ser) and track the list of >>outgoing devices. pci_liveupdate_preserve() notifies the PCI core that a >>device must be preserved across Live Update. pci_liveupdate_unpreserve() >>reverses this (cancels the preservation of the device). >> >>This tracking ensures the PCI core is fully aware of which devices may >>need special handling during shutdown and kexec, and so that it can be >>handed off to the next kernel. >> >>Signed-off-by: David Matlack >>--- >>drivers/pci/liveupdate.c | 101 ++++++++++++++++++++++++++++++++++++ >>include/linux/kho/abi/pci.h | 7 +-- >>include/linux/pci.h | 26 ++++++++++ >>3 files changed, 131 insertions(+), 3 deletions(-) >> >>diff --git a/include/linux/kho/abi/pci.h b/include/linux/kho/abi/pci.h >>index 5c0e92588c00..5b4c8d9e462c 100644 >>--- a/include/linux/kho/abi/pci.h >>+++ b/include/linux/kho/abi/pci.h >>@@ -23,19 +23,20 @@ >> * incrementing the version number in the PCI_LUO_FLB_COMPATIBLE string. >> */ >> >>-#define PCI_LUO_FLB_COMPATIBLE "pci-v1" >>+#define PCI_LUO_FLB_COMPATIBLE "pci-v2" >> >>/** >> * struct pci_dev_ser - Serialized state about a single PCI device. >> * >> * @domain: The device's PCI domain number (segment). >> * @bdf: The device's PCI bus, device, and function number. >>- * @reserved: Reserved (to naturally align struct pci_dev_ser). >>+ * @refcount: Reference count used by the PCI core to keep track of whether it >>+ * is done using a device's struct pci_dev_ser. nit: I was wondering why is this named refcount and why it is needed. It seems you are using it to track the preservation dependency between parent devices and leaf. Maybe add a comment to clarify that. >> */ >>struct pci_dev_ser { >> u32 domain; >> u16 bdf; >>- u16 reserved; >>+ u16 refcount; >>} __packed; >> >>/** Sami