[PATCH v4 08/27] vfio/cxl: Add the vfio-cxl module skeleton

[<mhonap@nvidia.com>]

From: Manish Honap <mhonap@nvidia.com>

Add the vfio-cxl module that vfio-pci loads on demand for CXL Type-2
devices. It registers a set of callbacks with vfio-pci-core at
module_init and drops them at exit; the callbacks are stubs here and
are filled in by later patches.

VFIO_CXL depends on CXL_BUS and builds as vfio-cxl.ko, which
request_module("vfio-cxl") resolves through MODULE_ALIAS.

Signed-off-by: Manish Honap <mhonap@nvidia.com>
---
 MAINTAINERS                          |  7 +++++
 drivers/vfio/pci/Kconfig             |  2 ++
 drivers/vfio/pci/Makefile            |  2 ++
 drivers/vfio/pci/cxl/Kconfig         | 11 ++++++++
 drivers/vfio/pci/cxl/Makefile        |  3 ++
 drivers/vfio/pci/cxl/vfio_cxl_core.c | 41 ++++++++++++++++++++++++++++
 6 files changed, 66 insertions(+)
 create mode 100644 drivers/vfio/pci/cxl/Kconfig
 create mode 100644 drivers/vfio/pci/cxl/Makefile
 create mode 100644 drivers/vfio/pci/cxl/vfio_cxl_core.c

diff --git a/MAINTAINERS b/MAINTAINERS
index c665bf8f1a28..aa8cecbc4cf2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -28312,6 +28312,13 @@ L:	kvm@vger.kernel.org
 S:	Maintained
 F:	drivers/vfio/cdx/*
 
+VFIO CXL DRIVER
+M:	Manish Honap <mhonap@nvidia.com>
+L:	kvm@vger.kernel.org
+L:	linux-cxl@vger.kernel.org
+S:	Supported
+F:	drivers/vfio/pci/cxl/
+
 VFIO DRIVER
 M:	Alex Williamson <alex@shazbot.org>
 L:	kvm@vger.kernel.org
diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
index 296bf01e185e..c3f54fc8ccc0 100644
--- a/drivers/vfio/pci/Kconfig
+++ b/drivers/vfio/pci/Kconfig
@@ -70,6 +70,8 @@ source "drivers/vfio/pci/virtio/Kconfig"
 
 source "drivers/vfio/pci/nvgrace-gpu/Kconfig"
 
+source "drivers/vfio/pci/cxl/Kconfig"
+
 source "drivers/vfio/pci/qat/Kconfig"
 
 source "drivers/vfio/pci/xe/Kconfig"
diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
index 6138f1bf241d..c3031070a1f3 100644
--- a/drivers/vfio/pci/Makefile
+++ b/drivers/vfio/pci/Makefile
@@ -21,6 +21,8 @@ obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio/
 
 obj-$(CONFIG_NVGRACE_GPU_VFIO_PCI) += nvgrace-gpu/
 
+obj-$(CONFIG_VFIO_CXL) += cxl/
+
 obj-$(CONFIG_QAT_VFIO_PCI) += qat/
 
 obj-$(CONFIG_XE_VFIO_PCI) += xe/
diff --git a/drivers/vfio/pci/cxl/Kconfig b/drivers/vfio/pci/cxl/Kconfig
new file mode 100644
index 000000000000..1392fa4ed15d
--- /dev/null
+++ b/drivers/vfio/pci/cxl/Kconfig
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config VFIO_CXL
+	tristate "VFIO support for CXL Type-2 devices"
+	depends on CXL_BUS && CXL_MEM
+	select VFIO_PCI_CORE
+	help
+	  Add CXL HDM handling to vfio-pci so a CXL Type-2 device, such as a
+	  CXL-attached accelerator, can be assigned to a virtual machine.
+	  vfio-pci loads this module on demand when it binds a CXL device.
+
+	  If you don't know what to do here, say N.
diff --git a/drivers/vfio/pci/cxl/Makefile b/drivers/vfio/pci/cxl/Makefile
new file mode 100644
index 000000000000..8501bf626108
--- /dev/null
+++ b/drivers/vfio/pci/cxl/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_VFIO_CXL) += vfio-cxl.o
+vfio-cxl-y := vfio_cxl_core.o
diff --git a/drivers/vfio/pci/cxl/vfio_cxl_core.c b/drivers/vfio/pci/cxl/vfio_cxl_core.c
new file mode 100644
index 000000000000..cbec7319452c
--- /dev/null
+++ b/drivers/vfio/pci/cxl/vfio_cxl_core.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * VFIO support for CXL Type-2 devices.
+ *
+ * Copyright (c) 2026 NVIDIA Corporation & Affiliates
+ */
+
+#include <linux/module.h>
+#include <linux/vfio_pci_core.h>
+
+static int vfio_cxl_init_device(struct vfio_pci_core_device *vdev)
+{
+	return 0;
+}
+
+static void vfio_cxl_release_device(struct vfio_pci_core_device *vdev)
+{
+}
+
+static const struct vfio_cxl_ops vfio_cxl_ops = {
+	.init_device	= vfio_cxl_init_device,
+	.release_device	= vfio_cxl_release_device,
+	.owner		= THIS_MODULE,
+};
+
+static int __init vfio_cxl_init(void)
+{
+	return vfio_pci_core_register_cxl_ops(&vfio_cxl_ops);
+}
+
+static void __exit vfio_cxl_exit(void)
+{
+	vfio_pci_core_unregister_cxl_ops(&vfio_cxl_ops);
+}
+
+module_init(vfio_cxl_init);
+module_exit(vfio_cxl_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("VFIO support for CXL Type-2 devices");
+MODULE_ALIAS("vfio-cxl");
-- 
2.25.1