From: Manish Honap <[email protected]> The HDM decoder register block lives in the component BAR that vfio-pci owns. The guest reads the decoder only through the trapped, read-only decoder region; it must not reach the physical registers through the BAR directly, and a host read of the range through a kernel mapping could abort as a fatal host SError.
Add the block to the generic excluded-range list with VFIO_PCI_EXCLUDE_MMAP | VFIO_PCI_EXCLUDE_READ | VFIO_PCI_EXCLUDE_WRITE similar to the MSI-X exclusion. Assisted-by: LLM Signed-off-by: Manish Honap <[email protected]> --- drivers/vfio/pci/cxl/vfio_cxl_core.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/drivers/vfio/pci/cxl/vfio_cxl_core.c b/drivers/vfio/pci/cxl/vfio_cxl_core.c index da04776356e4..37e8a3b54cfb 100644 --- a/drivers/vfio/pci/cxl/vfio_cxl_core.c +++ b/drivers/vfio/pci/cxl/vfio_cxl_core.c @@ -435,8 +435,25 @@ static int vfio_cxl_add_region(struct vfio_pci_core_device *vdev, u32 subtype, static int vfio_cxl_open_device(struct vfio_pci_core_device *vdev) { struct vfio_cxl_state *cxl = vdev->cxl; + struct pci_dev *pdev = vdev->pdev; int ret; + /* + * Keep the HDM decoder block out of the guest's direct BAR access: the + * guest reaches it only through the trapped decoder region, and a host + * read of the range through a kernel mapping could abort as an SError. + * Exclude it from mmap, fill reads with -1 and drop writes. The list is + * cleared on close, so re-add it per open. + */ + ret = vfio_pci_core_add_excluded_range(vdev, pdev->hdm->hdm_bar, + pdev->hdm->hdm_offset, + cxl->hdm_len, + VFIO_PCI_EXCLUDE_MMAP | + VFIO_PCI_EXCLUDE_READ | + VFIO_PCI_EXCLUDE_WRITE); + if (ret) + return ret; + /* * vfio_pci_core_disable() frees all dynamic regions on close, so register * them here per open rather than at bind. A failed first open never -- 2.25.1
