On Thu, 13 Aug 2026 15:06:13 +0530
<[email protected]> wrote:
> From: Manish Honap <[email protected]>
>
> Read the HDM region size from decoder 0, cached in pdev->hdm at
> enumeration, and use it to size the accelerator device state. A Type-2
> accelerator has no mailbox, so cxl_set_capacity() establishes the
> capacity that devm_cxl_probe_mem() then uses to join the device to the
> CXL topology and resolve the host physical range.
>
> Everything here is devm-scoped to the PCI device, so it is unwound when
> vfio-pci unbinds. If pdev->hdm is not populated yet, defer the bind.
>
> Signed-off-by: Manish Honap <[email protected]>
> ---
> drivers/vfio/pci/cxl/vfio_cxl_core.c | 53 ++++++++++++++++++++++++++++
> 1 file changed, 53 insertions(+)
>
> diff --git a/drivers/vfio/pci/cxl/vfio_cxl_core.c
> b/drivers/vfio/pci/cxl/vfio_cxl_core.c
> index cbec7319452c..125e11354a46 100644
> --- a/drivers/vfio/pci/cxl/vfio_cxl_core.c
> +++ b/drivers/vfio/pci/cxl/vfio_cxl_core.c
> @@ -6,15 +6,67 @@
> */
>
> #include <linux/module.h>
> +#include <linux/pci.h>
> +#include <linux/range.h>
> #include <linux/vfio_pci_core.h>
> +#include <cxl/cxl.h>
> +
> +/**
> + * struct vfio_cxl_state - per-device state for a vfio-cxl device
> + * @cxlds: CXL device state; kept first for devm_cxl_dev_state_create()
> + * @cxlmd: memory device joined to the CXL topology at bind
> + * @hpa_range: host physical range of the HDM region
> + */
> +struct vfio_cxl_state {
> + struct cxl_dev_state cxlds;
> + struct cxl_memdev *cxlmd;
> + struct range hpa_range;
> +};
>
> static int vfio_cxl_init_device(struct vfio_pci_core_device *vdev)
> {
> + struct pci_dev *pdev = vdev->pdev;
> + struct vfio_cxl_state *cxl;
> + struct cxl_memdev *cxlmd;
> + u64 hdm_size, serial;
> + u16 dvsec;
> + int ret;
> +
> + /* pdev->hdm is populated at PCI enumeration; defer until it is. */
> + if (!pdev->hdm)
> + return -EPROBE_DEFER;
How would a device get to a PCI driver probe function without being
enumerated by the PCI core? This also looks like an infinite loop; if
there's an error setting the hdm pointer, this is forever deferred.
> +
> + hdm_size = range_len(&pdev->hdm->settings[0].hpa_range);
We don't validate the number of hdm ranges until the next patch.
> + if (!hdm_size)
> + return -ENXIO;
> +
> + dvsec = pci_find_dvsec_capability(pdev, PCI_VENDOR_ID_CXL,
> + PCI_DVSEC_CXL_DEVICE);
> + serial = pci_get_dsn(pdev);
> +
> + cxl = devm_cxl_dev_state_create(&pdev->dev, CXL_DEVTYPE_DEVMEM, serial,
> + dvsec, struct vfio_cxl_state, cxlds,
> + false);
> + if (!cxl)
> + return -ENOMEM;
> +
> + ret = cxl_set_capacity(&cxl->cxlds, hdm_size);
> + if (ret)
> + return ret;
> +
> + cxlmd = devm_cxl_probe_mem(&cxl->cxlds, &cxl->hpa_range);
> + if (IS_ERR(cxlmd))
> + return PTR_ERR(cxlmd);
> +
> + cxl->cxlmd = cxlmd;
> + vdev->cxl = cxl;
> +
> return 0;
> }
>
> static void vfio_cxl_release_device(struct vfio_pci_core_device *vdev)
> {
> + vdev->cxl = NULL;
> }
>
> static const struct vfio_cxl_ops vfio_cxl_ops = {
> @@ -39,3 +91,4 @@ module_exit(vfio_cxl_exit);
> MODULE_LICENSE("GPL");
> MODULE_DESCRIPTION("VFIO support for CXL Type-2 devices");
> MODULE_ALIAS("vfio-cxl");
I missed commenting on this in the previous patch, but why do we need to
declare an alias to the name the module already has? AIUI this is for
providing an alternate name for the actual name of the module. Thanks,
Alex
> +MODULE_IMPORT_NS("CXL");
