On Thu, Sep 17, 2026 at 12:05:34AM +0800, [email protected] wrote: > 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. >
Hi Manish, I think we need to block eventfd write and BAR DMA as well ? Have some comments below. > 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); This adds the HDM reg to the exclusion list, but the eventfd and BAR DMA path doesn't check that. Maybe we need to block those 2 path as well ? Best regards, Richard Cheng. > + 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 > >
