From: Manish Honap Add an opt-out so users can keep vfio-pci's CXL extensions out of the path for individual devices or for an entire vfio-pci instance. The runtime gates are: - Module parameter vfio_pci.disable_cxl (bool, 0444). Setting disable_cxl=1 at modprobe time makes vfio_pci_probe() set vdev->disable_cxl on every device it binds. - Variant drivers (nvgrace, mlx5, and others) may set vdev->disable_cxl in their own probe for per-device control without the module parameter. The bit lives on struct vfio_pci_core_device so it is reachable from any variant. vfio_pci_core_init_dev() consults vdev->disable_cxl before it probes for a CXL device, so a device that opts out is driven as plain vfio-pci: vfio-cxl is not loaded, init_device() never runs, and the device gets no VFIO_DEVICE_FLAGS_CXL, no HDM or component-register regions, and no DVSEC virtualization. The module parameter is built only when CONFIG_VFIO_CXL is enabled; the disable_cxl bit itself is unconditional so a variant driver can set it regardless. This mirrors the long-standing disable_denylist opt-out. Signed-off-by: Manish Honap --- drivers/vfio/pci/vfio_pci.c | 9 +++++++++ drivers/vfio/pci/vfio_pci_core.c | 8 +++++--- include/linux/vfio_pci_core.h | 1 + 3 files changed, 15 insertions(+), 3 deletions(-) diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c index 830369ff878d..0ad041fffe48 100644 --- a/drivers/vfio/pci/vfio_pci.c +++ b/drivers/vfio/pci/vfio_pci.c @@ -60,6 +60,12 @@ static bool disable_denylist; module_param(disable_denylist, bool, 0444); MODULE_PARM_DESC(disable_denylist, "Disable use of device denylist. Disabling the denylist allows binding to devices with known errata that may lead to exploitable stability or security issues when accessed by untrusted users."); +#if IS_ENABLED(CONFIG_VFIO_CXL) +static bool disable_cxl; +module_param(disable_cxl, bool, 0444); +MODULE_PARM_DESC(disable_cxl, "Disable CXL Type-2 extensions for all devices bound to vfio-pci. A variant driver may instead set vdev->disable_cxl in its own .init callback."); +#endif + static bool vfio_pci_dev_in_denylist(struct pci_dev *pdev) { switch (pdev->vendor) { @@ -142,6 +148,9 @@ static int vfio_pci_init_dev(struct vfio_device *core_vdev) #ifdef CONFIG_VFIO_PCI_VGA vdev->disable_vga = disable_vga; #endif +#if IS_ENABLED(CONFIG_VFIO_CXL) + vdev->disable_cxl = disable_cxl; +#endif return vfio_pci_core_init_dev(core_vdev); } diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index 0fed8e00bc1d..4b51a0f1e847 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -2423,10 +2423,12 @@ int vfio_pci_core_init_dev(struct vfio_device *core_vdev) xa_init(&vdev->ctx); /* - * Load vfio-cxl on demand for a CXL device. If it is absent, drive the - * device as plain vfio-pci rather than failing the bind. + * Load vfio-cxl on demand for a CXL device unless the user opted out. + * If it is opted out or absent, drive the device as plain vfio-pci + * rather than failing the bind. */ - if (pcie_is_cxl(vdev->pdev) && vfio_pci_is_cxl_type2(vdev->pdev)) { + if (!vdev->disable_cxl && pcie_is_cxl(vdev->pdev) && + vfio_pci_is_cxl_type2(vdev->pdev)) { const struct vfio_cxl_ops *ops; request_module("vfio-cxl"); diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h index 18e206a35d8c..8e3723a55c17 100644 --- a/include/linux/vfio_pci_core.h +++ b/include/linux/vfio_pci_core.h @@ -158,6 +158,7 @@ struct vfio_pci_core_device { bool disable_idle_d3:1; bool nointxmask:1; bool disable_vga:1; + bool disable_cxl:1; /* Flags modified at runtime - dedicated storage unit */ bool needs_reset; bool pm_intx_masked; -- 2.25.1