[PATCH kernel 3/3] vfio-pci: Allow to expose MSI-X table to userspace if interrupt remapping is enabled

[Alexey Kardashevskiy]

From: Yongji Xie <elohi...@gmail.com>

This patch tries to expose MSI-X tables to userspace if hardware
enables interrupt remapping which can ensure that a given PCI
device can only shoot the MSIs assigned for it. So we could
never worry that userspace driver can hurt other devices by
writing to the exposed MSI-X table directly.

Signed-off-by: Yongji Xie <xyj...@linux.vnet.ibm.com>
Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
---
 drivers/vfio/pci/vfio_pci.c      | 18 +++++++++++++++---
 drivers/vfio/pci/vfio_pci_rdwr.c |  3 ++-
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 324c52e3a1a4..700e9d04dab5 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -564,8 +564,12 @@ static int msix_sparse_mmap_cap(struct vfio_pci_device 
*vdev,
 
        end = pci_resource_len(vdev->pdev, vdev->msix_bar);
 
-       /* If MSI-X table is aligned to the start or end, only one area */
-       if (((vdev->msix_offset & PAGE_MASK) == 0) ||
+       /*
+        * If MSI-X table is allowed to mmap because of the capability
+        * of IRQ remapping or aligned to the start or end, only one area
+        */
+       if ((vdev->pdev->bus->bus_flags & PCI_BUS_FLAGS_MSI_REMAP) ||
+           ((vdev->msix_offset & PAGE_MASK) == 0) ||
            (PAGE_ALIGN(vdev->msix_offset + vdev->msix_size) >= end))
                nr_areas = 1;
 
@@ -577,6 +581,12 @@ static int msix_sparse_mmap_cap(struct vfio_pci_device 
*vdev,
 
        sparse->nr_areas = nr_areas;
 
+       if (vdev->pdev->bus->bus_flags & PCI_BUS_FLAGS_MSI_REMAP) {
+               sparse->areas[i].offset = 0;
+               sparse->areas[i].size = end;
+               goto out;
+       }
+
        if (vdev->msix_offset & PAGE_MASK) {
                sparse->areas[i].offset = 0;
                sparse->areas[i].size = vdev->msix_offset & PAGE_MASK;
@@ -590,6 +600,7 @@ static int msix_sparse_mmap_cap(struct vfio_pci_device 
*vdev,
                i++;
        }
 
+out:
        ret = vfio_info_add_capability(caps, VFIO_REGION_INFO_CAP_SPARSE_MMAP,
                                       sparse);
        kfree(sparse);
@@ -1115,7 +1126,8 @@ static int vfio_pci_mmap(void *device_data, struct 
vm_area_struct *vma)
        if (req_start + req_len > phys_len)
                return -EINVAL;
 
-       if (index == vdev->msix_bar) {
+       if (index == vdev->msix_bar &&
+               !(pdev->bus->bus_flags & PCI_BUS_FLAGS_MSI_REMAP)) {
                /*
                 * Disallow mmaps overlapping the MSI-X table; users don't
                 * get to touch this directly.  We could find somewhere
diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
index 357243d76f10..5378f2c3ac8e 100644
--- a/drivers/vfio/pci/vfio_pci_rdwr.c
+++ b/drivers/vfio/pci/vfio_pci_rdwr.c
@@ -164,7 +164,8 @@ ssize_t vfio_pci_bar_rw(struct vfio_pci_device *vdev, char 
__user *buf,
        } else
                io = vdev->barmap[bar];
 
-       if (bar == vdev->msix_bar) {
+       if (bar == vdev->msix_bar &&
+               !(pdev->bus->bus_flags & PCI_BUS_FLAGS_MSI_REMAP)) {
                x_start = vdev->msix_offset;
                x_end = vdev->msix_offset + vdev->msix_size;
        }
-- 
2.11.0