Merge branch 'lu-pci-preservation' into next

3 files changed, 175 insertions, 0 deletions

diff --git a/include/linux/kho/abi/pci.h b/include/linux/kho/abi/pci.h
new file mode 100644
index 000000000000..c2e3a5949f73
--- /dev/null
+++ b/include/linux/kho/abi/pci.h
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright (c) 2026, Google LLC.
+ * David Matlack <dmatlack@google.com>
+ */
+
+#ifndef _LINUX_KHO_ABI_PCI_H
+#define _LINUX_KHO_ABI_PCI_H
+
+#include <linux/bug.h>
+#include <linux/compiler.h>
+#include <linux/stddef.h>
+#include <linux/types.h>
+
+/**
+ * DOC: PCI File-Lifecycle Bound (FLB) Live Update ABI
+ *
+ * The PCI core preserves its state across kexec as Live Update
+ * File-Lifecycle Bound (FLB) data, identified by the compatible string
+ * ``"pci"`` and laid out as described by the structs below.
+ *
+ * This layout is a contract between kernels. Rather than being versioned, it
+ * is extended according to the following rules:
+ *
+ *  * Existing fields must never be moved, resized, removed, or have their
+ *    meaning changed. New fields may only be appended to the end of a struct.
+ *
+ *  * A bit set in ``pci_ser.required_flags`` marks a feature that the next
+ *    kernel must understand to safely take over the preserved devices. The
+ *    next kernel panics if it finds a bit it does not know how to handle.
+ *
+ *  * A bit set in ``pci_ser.optional_flags`` marks a feature that the next
+ *    kernel can safely ignore if it does not understand it.
+ *
+ *  * Fields appended to struct pci_ser must be accompanied by a flag that
+ *    indicates they are present, since the size of struct pci_ser is not
+ *    recorded.
+ *
+ *  * The size of each struct pci_dev_ser is recorded in
+ *    ``pci_ser.dev_ser_size`` and is never smaller than
+ *    ``PCI_DEV_SER_MIN_SIZE``. The next kernel ignores any fields beyond the
+ *    ones it knows about, and must handle entries that are smaller than its
+ *    own struct pci_dev_ser.
+ */
+
+#define PCI_LUO_FLB_COMPATIBLE "pci"
+
+/**
+ * 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.
+ * @refcount: Reference count used by the PCI core to keep track of whether it
+ *            is done using a device's struct pci_dev_ser. The value of the
+ *            reference count is equal to the number of preserved devices at or
+ *            below it in the PCI hierarchy when the struct pci_dev_ser is in
+ *            use, and 0 otherwise.
+ */
+struct pci_dev_ser {
+	u32 domain;
+	u16 bdf;
+	u16 refcount;
+} __packed;
+
+/*
+ * The size of struct pci_dev_ser when this ABI was introduced. Since fields
+ * can only be appended, every struct pci_dev_ser is at least this large.
+ */
+#define PCI_DEV_SER_MIN_SIZE offsetofend(struct pci_dev_ser, refcount)
+
+/**
+ * struct pci_ser - PCI Subsystem Live Update State
+ *
+ * This struct tracks state about all devices that are being preserved across
+ * a Live Update for the next kernel. It contains only state owned by the PCI
+ * core; the state a driver needs to resume its device is preserved separately
+ * by that driver.
+ *
+ * @required_flags: Features that the next kernel must support to take over
+ *                  the preserved devices. No flags are currently defined.
+ * @optional_flags: Features that the next kernel may ignore if it does not
+ *                  support them. No flags are currently defined.
+ * @dev_ser_size: The size in bytes of each struct pci_dev_ser in @devices.
+ * @nr_devices: The number of devices that were preserved.
+ * @devices: Physical address of the first KHO block containing pci_dev_ser.
+ */
+struct pci_ser {
+	u64 required_flags;
+	u64 optional_flags;
+	u32 dev_ser_size;
+	u32 nr_devices;
+	u64 devices;
+} __packed;
+
+#endif /* _LINUX_KHO_ABI_PCI_H */
diff --git a/include/linux/pci.h b/include/linux/pci.h
index aa3765a20a96..6482549a8417 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -43,6 +43,7 @@
 #include <uapi/linux/pci.h>
 
 #include <linux/pci_ids.h>
+#include <linux/pci_liveupdate.h>
 
 #define PCI_STATUS_ERROR_BITS (PCI_STATUS_DETECTED_PARITY  | \
 			       PCI_STATUS_SIG_SYSTEM_ERROR | \
@@ -599,6 +600,9 @@ struct pci_dev {
 	u8		tph_mode;	/* TPH mode */
 	u8		tph_req_type;	/* TPH requester type */
 #endif
+#ifdef CONFIG_PCI_LIVEUPDATE
+	struct pci_liveupdate liveupdate;
+#endif
 };
 
 static inline struct pci_dev *pci_physfn(struct pci_dev *dev)
@@ -836,6 +840,9 @@ static inline struct pci_dev *pci_upstream_bridge(struct pci_dev *dev)
 	return dev->bus->self;
 }
 
+#define for_each_pci_dev_in_path(dev) \
+	for (; dev; dev = pci_upstream_bridge(dev))
+
 #ifdef CONFIG_PCI_MSI
 static inline bool pci_dev_msi_enabled(struct pci_dev *pci_dev)
 {
diff --git a/include/linux/pci_liveupdate.h b/include/linux/pci_liveupdate.h
new file mode 100644
index 000000000000..bb79348769b7
--- /dev/null
+++ b/include/linux/pci_liveupdate.h
@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * PCI Live Update support (Public/Driver API)
+ *
+ * Copyright (c) 2026, Google LLC.
+ * David Matlack <dmatlack@google.com>
+ */
+#ifndef LINUX_PCI_LIVEUPDATE_H
+#define LINUX_PCI_LIVEUPDATE_H
+
+#include <linux/kho/abi/pci.h>
+#include <linux/liveupdate.h>
+#include <linux/spinlock_types.h>
+#include <linux/types.h>
+
+/**
+ * struct pci_liveupdate - PCI Live Update state for a struct pci_dev
+ * @outgoing: State preserved for the next kernel.
+ * @incoming: State preserved by the previous kernel.
+ * @was_incoming: True if this struct pci_dev was incoming-preserved when it was
+ *                set up, i.e. it was matched to state preserved by the previous
+ *                kernel. Unlike @incoming, this is never cleared, so it stays
+ *                true after the device finishes participating in Live Update.
+ * @frozen: True if the outgoing preservation status of this device is frozen
+ *          and thus cannot be changed.
+ */
+struct pci_liveupdate {
+	struct pci_dev_ser *outgoing;
+	struct pci_dev_ser *incoming;
+	bool was_incoming;
+	bool frozen;
+};
+
+struct pci_dev;
+
+#ifdef CONFIG_PCI_LIVEUPDATE
+int pci_liveupdate_register_flb(struct liveupdate_file_handler *fh);
+void pci_liveupdate_unregister_flb(struct liveupdate_file_handler *fh);
+int pci_liveupdate_preserve(struct pci_dev *dev);
+void pci_liveupdate_unpreserve(struct pci_dev *dev);
+void pci_liveupdate_finish(struct pci_dev *dev);
+bool pci_liveupdate_is_incoming(struct pci_dev *dev);
+#else
+static inline int pci_liveupdate_register_flb(struct liveupdate_file_handler *fh)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void pci_liveupdate_unregister_flb(struct liveupdate_file_handler *fh)
+{
+}
+
+static inline int pci_liveupdate_preserve(struct pci_dev *dev)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void pci_liveupdate_unpreserve(struct pci_dev *dev)
+{
+}
+
+static inline void pci_liveupdate_finish(struct pci_dev *dev)
+{
+}
+
+static inline bool pci_liveupdate_is_incoming(struct pci_dev *dev)
+{
+	return false;
+}
+#endif
+
+#endif /* LINUX_PCI_LIVEUPDATE_H */