Re: [RFC PATCH v3 5/5] vfio-pci: Allow to mmap MSI-X table if host bridge supports filtering of MSIs

[Alex Williamson]

On Fri, 2016-01-15 at 15:06 +0800, Yongji Xie wrote:
> Current vfio-pci implementation disallows to mmap MSI-X
> table in case that user get to touch this directly.
>Â
> But we should allow to mmap these MSI-X tables if the PCI
> host bridge supports filtering of MSIs.
>Â
> Signed-off-by: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
> ---
> Âdrivers/vfio/pci/vfio_pci.c |ÂÂÂÂ6 ++++--
> Â1 file changed, 4 insertions(+), 2 deletions(-)
>Â
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index 11fd0f0..4d68f6a 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -555,7 +555,8 @@ static long vfio_pci_ioctl(void *device_data,
> Â			ÂÂÂÂIORESOURCE_MEM && !pci_resources_share_page(pdev,
> Â			ÂÂÂÂinfo.index)) {
> Â				info.flags |= VFIO_REGION_INFO_FLAG_MMAP;
> -				if (info.index == vdev->msix_bar) {
> +				if (!pci_host_bridge_msi_filtered_enabled(pdev) &&
> +				ÂÂÂÂinfo.index == vdev->msix_bar) {
> Â					ret = msix_sparse_mmap_cap(vdev, &caps);
> Â					if (ret)
> Â						return ret;
> @@ -967,7 +968,8 @@ static int vfio_pci_mmap(void *device_data, struct vm_area_struct *vma)
> Â	if (phys_len < PAGE_SIZE || req_start + req_len > phys_len)
> Â		return -EINVAL;
> Â
> -	if (index == vdev->msix_bar) {
> +	if (!pci_host_bridge_msi_filtered_enabled(pdev) &&
> +	ÂÂÂÂindex == vdev->msix_bar) {
> Â		/*
> Â		Â* Disallow mmaps overlapping the MSI-X table; users don't
> Â		Â* get to touch this directly.ÂÂWe could find somewhere

What about read()/write() access, why would we allow mmap() but not
those?