Re: [PATCH v5 11/27] vfio/pci: Virtualize the CXL DVSEC in vfio_pci_config.c

[Alex Williamson <alex@shazbot.org>]

On Thu, 17 Sep 2026 00:05:24 +0530
<mhonap@nvidia.com> wrote:
> +/* Virtualize the CXL DVSEC so a guest cannot reprogram the device through it. */
> +static int vfio_cxl_dvsec_init(struct vfio_pci_core_device *vdev)
> +{
> +	struct pci_dev *pdev = vdev->pdev;
> +	u32 dword;
> +	u16 dvsec;
> +	int len, ret;
> +
> +	dvsec = pci_find_dvsec_capability(pdev, PCI_VENDOR_ID_CXL,
> +					  PCI_DVSEC_CXL_DEVICE);
> +	if (!dvsec)
> +		return 0;
> +
> +	ret = pci_read_config_dword(pdev, dvsec + PCI_DVSEC_HEADER1, &dword);
> +	if (ret)
> +		return pcibios_err_to_errno(ret);
> +	len = PCI_DVSEC_HEADER1_LEN(dword);
> +
> +	/*
> +	 * The virtualization writes fixed DVSEC offsets up to Status2 (the reset
> +	 * doorbell stamps it). A device that reports a shorter DVSEC is not a
> +	 * usable Type-2 function; leave it as plain vfio-pci rather than index the
> +	 * device-length-sized perm allocation past its end.
> +	 */
> +	if (len < PCI_DVSEC_CXL_STATUS2 + 2)
> +		return 0;
> +
> +	vdev->cxl_perm = kmalloc_obj(struct perm_bits, GFP_KERNEL_ACCOUNT);
> +	if (!vdev->cxl_perm)
> +		return -ENOMEM;
> +
> +	ret = init_cxl_dvsec_perm(vdev->cxl_perm, len);
> +	if (ret) {
> +		kfree(vdev->cxl_perm);
> +		vdev->cxl_perm = NULL;
> +		return ret;
> +	}
> +
> +	vdev->cxl_dvsec = dvsec;
> +	vdev->cxl_dvsec_len = len;

cxl_dvsec_len is never used here or elsewhere in the series.  Thanks,

Alex

> +
> +	return 0;
> +}
> +