From: Manish Honap <[email protected]> A CXL device needs the vfio-cxl callbacks, but pulling vfio-cxl and the CXL core in unconditionally would bloat every vfio-pci setup. Detect a CXL Type-2 device at bind and request_module("vfio-cxl") only then, then hand the device to the registered ops.
Each bound CXL device pins the provider through vfio_pci_get_cxl_ops() (try_module_get) and drops it with vfio_pci_put_cxl_ops() at release, so vfio-cxl can unload once no CXL device is bound. If the provider is absent the device is driven as plain vfio-pci. A built-in provider whose initcall has not run yet is waited for with -EPROBE_DEFER; the deferred-probe machinery will retry the bind once the provider registers. Assisted-by: LLM Signed-off-by: Manish Honap <[email protected]> --- drivers/vfio/pci/vfio_pci_core.c | 84 ++++++++++++++++++++++++++++++++ include/linux/vfio_pci_core.h | 3 ++ 2 files changed, 87 insertions(+) diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index 2cc5dd20396c..9eede1e56ab5 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -2202,6 +2202,84 @@ void vfio_pci_core_unregister_cxl_ops(const struct vfio_cxl_ops *ops) } EXPORT_SYMBOL_GPL(vfio_pci_core_unregister_cxl_ops); +static const struct vfio_cxl_ops *vfio_pci_get_cxl_ops(void) +{ + guard(rwsem_read)(&vfio_pci_cxl_ops_rwsem); + + if (vfio_pci_cxl_ops && try_module_get(vfio_pci_cxl_ops->owner)) + return vfio_pci_cxl_ops; + + return NULL; +} + +static void vfio_pci_put_cxl_ops(const struct vfio_cxl_ops *ops) +{ + module_put(ops->owner); +} + +/* + * A CXL Type-2 device advertises both CXL.cache and CXL.mem in its CXL DVSEC. + * pcie_is_cxl() is also true for Type-1 (cache only) and Type-3 (mem only) + * devices, which the vfio-cxl provider does not handle, so confirm the Type-2 + * identity before engaging it. + */ +static bool vfio_pci_is_cxl_type2(struct pci_dev *pdev) +{ + u16 dvsec, cap; + + if (!pcie_is_cxl(pdev)) + return false; + + dvsec = pci_find_dvsec_capability(pdev, PCI_VENDOR_ID_CXL, + PCI_DVSEC_CXL_DEVICE); + if (!dvsec) + return false; + + if (pci_read_config_word(pdev, dvsec + PCI_DVSEC_CXL_CAP, &cap)) + return false; + + return (cap & PCI_DVSEC_CXL_CACHE_CAPABLE) && + (cap & PCI_DVSEC_CXL_MEM_CAPABLE); +} + +/* + * Load vfio-cxl on demand for a CXL Type-2 device and hand the device to its + * ops. If the provider is absent the device is driven as plain vfio-pci; a + * built-in provider whose initcall has not run yet is waited for with + * -EPROBE_DEFER. + */ +static int vfio_pci_core_cxl_init(struct vfio_pci_core_device *vdev) +{ + const struct vfio_cxl_ops *ops; + int ret; + + if (!vfio_pci_is_cxl_type2(vdev->pdev)) + return 0; + + request_module("vfio-cxl"); + ops = vfio_pci_get_cxl_ops(); + if (!ops) + return IS_BUILTIN(CONFIG_VFIO_CXL) ? -EPROBE_DEFER : 0; + + ret = ops->init(vdev); + if (ret) { + vfio_pci_put_cxl_ops(ops); + return ret; + } + + vdev->cxl_ops = ops; + return 0; +} + +static void vfio_pci_core_cxl_release(struct vfio_pci_core_device *vdev) +{ + if (!vdev->cxl_ops) + return; + + vdev->cxl_ops->release(vdev); + vfio_pci_put_cxl_ops(vdev->cxl_ops); +} + int vfio_pci_core_init_dev(struct vfio_device *core_vdev) { struct vfio_pci_core_device *vdev = @@ -2223,6 +2301,10 @@ int vfio_pci_core_init_dev(struct vfio_device *core_vdev) init_rwsem(&vdev->memory_lock); xa_init(&vdev->ctx); + ret = vfio_pci_core_cxl_init(vdev); + if (ret) + return ret; + return 0; } EXPORT_SYMBOL_GPL(vfio_pci_core_init_dev); @@ -2232,6 +2314,8 @@ void vfio_pci_core_release_dev(struct vfio_device *core_vdev) struct vfio_pci_core_device *vdev = container_of(core_vdev, struct vfio_pci_core_device, vdev); + vfio_pci_core_cxl_release(vdev); + mutex_destroy(&vdev->igate); mutex_destroy(&vdev->ioeventfds_lock); kfree(vdev->region); diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h index 9fe0d1a3a370..7f3a2bcb5830 100644 --- a/include/linux/vfio_pci_core.h +++ b/include/linux/vfio_pci_core.h @@ -29,6 +29,7 @@ struct vfio_pci_core_device; struct vfio_pci_region; struct p2pdma_provider; struct dma_buf_attachment; +struct vfio_cxl_state; struct vfio_pci_eventfd { struct eventfd_ctx *ctx; @@ -109,6 +110,8 @@ struct vfio_pci_core_device { struct vfio_device vdev; struct pci_dev *pdev; const struct vfio_pci_device_ops *pci_ops; + const struct vfio_cxl_ops *cxl_ops; + struct vfio_cxl_state *cxl; void __iomem *barmap[PCI_STD_NUM_BARS]; bool bar_mmap_supported[PCI_STD_NUM_BARS]; /* Flags modified at runtime - dedicated storage unit */ -- 2.25.1
