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 build-time gate is CONFIG_VFIO_PCI_CXL; 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 (mlx5, pds, hisi, nvgrace, xe, etc.) may set vdev->disable_cxl=true in their own probe for per-device control without needing the module parameter. The bit lives on struct vfio_pci_core_device so it's reachable from any variant. vfio_pci_cxl_acquire() consults vdev->disable_cxl as the very first check and returns -ENODEV when set, which makes vfio-pci-core treat the device as a plain (non-CXL) PCI passthrough — no CAP_CXL, no HDM or COMP_REGS VFIO regions, no DVSEC clipping shim. This mirrors the long-standing disable_denylist opt-out shape. Signed-off-by: Manish Honap --- drivers/vfio/pci/cxl/vfio_cxl_core.c | 9 +++++++++ drivers/vfio/pci/vfio_pci.c | 9 +++++++++ include/linux/vfio_pci_core.h | 1 + 3 files changed, 19 insertions(+) diff --git a/drivers/vfio/pci/cxl/vfio_cxl_core.c b/drivers/vfio/pci/cxl/vfio_cxl_core.c index 8a00b776d7c7..905f74f4e725 100644 --- a/drivers/vfio/pci/cxl/vfio_cxl_core.c +++ b/drivers/vfio/pci/cxl/vfio_cxl_core.c @@ -234,6 +234,15 @@ int vfio_pci_cxl_acquire(struct vfio_pci_core_device *vdev) u16 dvsec; int rc; + /* + * Honour the per-device opt-out (set by vfio-pci's module + * parameter disable_cxl, or by a variant driver before + * registration). Returning -ENODEV here makes the caller + * treat this device as plain vfio-pci. + */ + if (vdev->disable_cxl) + return -ENODEV; + if (!pcie_is_cxl(pdev)) return -ENODEV; diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c index 0c771064c0b8..fd226cb65d8b 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_PCI_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. Variant drivers may instead set vdev->disable_cxl in their probe for per-device control without needing this parameter."); +#endif + static bool vfio_pci_dev_in_denylist(struct pci_dev *pdev) { switch (pdev->vendor) { @@ -166,6 +172,9 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id) return PTR_ERR(vdev); dev_set_drvdata(&pdev->dev, vdev); +#if IS_ENABLED(CONFIG_VFIO_PCI_CXL) + vdev->disable_cxl = disable_cxl; +#endif vdev->pci_ops = &vfio_pci_dev_ops; ret = vfio_pci_core_register_device(vdev); if (ret) diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h index 541c1911e090..20e9599b3bd7 100644 --- a/include/linux/vfio_pci_core.h +++ b/include/linux/vfio_pci_core.h @@ -127,6 +127,7 @@ struct vfio_pci_core_device { bool needs_pm_restore:1; bool pm_intx_masked:1; bool pm_runtime_engaged:1; + bool disable_cxl:1; struct pci_saved_state *pci_saved_state; struct pci_saved_state *pm_save; int ioeventfds_nr; -- 2.25.1