linux-kernel - [RFC PATCH 05/21] vfio/pci: Register VFIO live update file handler to Live Update Orchestrator

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Message-ID: <20251018000713.677779-6-vipinsh@google.com>
Date: Fri, 17 Oct 2025 17:06:57 -0700
From: Vipin Sharma <vipinsh@...gle.com>
To: bhelgaas@...gle.com, alex.williamson@...hat.com, pasha.tatashin@...een.com, 
	dmatlack@...gle.com, jgg@...pe.ca, graf@...zon.com
Cc: pratyush@...nel.org, gregkh@...uxfoundation.org, chrisl@...nel.org, 
	rppt@...nel.org, skhawaja@...gle.com, parav@...dia.com, saeedm@...dia.com, 
	kevin.tian@...el.com, jrhilke@...gle.com, david@...hat.com, 
	jgowans@...zon.com, dwmw2@...radead.org, epetron@...zon.de, 
	junaids@...gle.com, linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, 
	kvm@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	Vipin Sharma <vipinsh@...gle.com>
Subject: [RFC PATCH 05/21] vfio/pci: Register VFIO live update file handler to
 Live Update Orchestrator

Register VFIO live update file handler to Live Update Orchestrator.
Provide stub implementation of the handler callbacks.

Adding live update support in VFIO will enable a VFIO PCI device to work
uninterrupted while the host kernel is being updated through a kexec
reboot.

Signed-off-by: Vipin Sharma <vipinsh@...gle.com>
---
 drivers/vfio/pci/Makefile              |  1 +
 drivers/vfio/pci/vfio_pci_core.c       |  1 +
 drivers/vfio/pci/vfio_pci_liveupdate.c | 44 ++++++++++++++++++++++++++
 drivers/vfio/pci/vfio_pci_priv.h       |  6 ++++
 4 files changed, 52 insertions(+)
 create mode 100644 drivers/vfio/pci/vfio_pci_liveupdate.c

diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
index cf00c0a7e55c..929df22c079b 100644
--- a/drivers/vfio/pci/Makefile
+++ b/drivers/vfio/pci/Makefile
@@ -2,6 +2,7 @@
 
 vfio-pci-core-y := vfio_pci_core.o vfio_pci_intrs.o vfio_pci_rdwr.o vfio_pci_config.o
 vfio-pci-core-$(CONFIG_VFIO_PCI_ZDEV_KVM) += vfio_pci_zdev.o
+vfio-pci-core-$(CONFIG_LIVEUPDATE) += vfio_pci_liveupdate.o
 obj-$(CONFIG_VFIO_PCI_CORE) += vfio-pci-core.o
 
 vfio-pci-y := vfio_pci.o
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 7dcf5439dedc..0894673a9262 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -2568,6 +2568,7 @@ static void vfio_pci_core_cleanup(void)
 static int __init vfio_pci_core_init(void)
 {
 	/* Allocate shared config space permission data used by all devices */
+	vfio_pci_liveupdate_init();
 	return vfio_pci_init_perm_bits();
 }
 
diff --git a/drivers/vfio/pci/vfio_pci_liveupdate.c b/drivers/vfio/pci/vfio_pci_liveupdate.c
new file mode 100644
index 000000000000..088f7698a72c
--- /dev/null
+++ b/drivers/vfio/pci/vfio_pci_liveupdate.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Liveupdate support for VFIO devices.
+ *
+ * Copyright (c) 2025, Google LLC.
+ * Vipin Sharma <vipinsh@...gle.com>
+ */
+
+#include <linux/liveupdate.h>
+#include <linux/errno.h>
+
+#include "vfio_pci_priv.h"
+
+static int vfio_pci_liveupdate_retrieve(struct liveupdate_file_handler *handler,
+					u64 data, struct file **file)
+{
+	return -EOPNOTSUPP;
+}
+
+static bool vfio_pci_liveupdate_can_preserve(struct liveupdate_file_handler *handler,
+					     struct file *file)
+{
+	return -EOPNOTSUPP;
+}
+
+static const struct liveupdate_file_ops vfio_pci_luo_fops = {
+	.retrieve = vfio_pci_liveupdate_retrieve,
+	.can_preserve = vfio_pci_liveupdate_can_preserve,
+	.owner = THIS_MODULE,
+};
+
+static struct liveupdate_file_handler vfio_pci_luo_handler = {
+	.ops = &vfio_pci_luo_fops,
+	.compatible = "vfio-v1",
+};
+
+void __init vfio_pci_liveupdate_init(void)
+{
+	int err = liveupdate_register_file_handler(&vfio_pci_luo_handler);
+
+	if (err)
+		pr_err("VFIO PCI liveupdate file handler register failed, error %d.\n", err);
+}
diff --git a/drivers/vfio/pci/vfio_pci_priv.h b/drivers/vfio/pci/vfio_pci_priv.h
index a9972eacb293..7779fd744ff5 100644
--- a/drivers/vfio/pci/vfio_pci_priv.h
+++ b/drivers/vfio/pci/vfio_pci_priv.h
@@ -107,4 +107,10 @@ static inline bool vfio_pci_is_vga(struct pci_dev *pdev)
 	return (pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA;
 }
 
+#ifdef CONFIG_LIVEUPDATE
+void vfio_pci_liveupdate_init(void);
+#else
+static inline void vfio_pci_liveupdate_init(void) { }
+#endif /* CONFIG_LIVEUPDATE */
+
 #endif
-- 
2.51.0.858.gf9c4a03a3a-goog