Current vfio-pci implementation disallows to mmap MSI-X
table in case that user get to touch this directly.

But we should allow to mmap these MSI-X tables if IOMMU
supports interrupt remapping which can ensure that a
given pci device can only shoot the MSIs assigned for it.

Signed-off-by: Yongji Xie <xyj...@linux.vnet.ibm.com>
---
 drivers/vfio/pci/vfio_pci.c      |    8 +++++---
 drivers/vfio/pci/vfio_pci_rdwr.c |    4 +++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 49d7a69..d6f4788 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -592,13 +592,14 @@ static long vfio_pci_ioctl(void *device_data,
                            IORESOURCE_MEM && !pci_resources_share_page(pdev,
                            info.index)) {
                                info.flags |= VFIO_REGION_INFO_FLAG_MMAP;
-                               if (info.index == vdev->msix_bar) {
+                               if (!iommu_capable(pdev->dev.bus,
+                                       IOMMU_CAP_INTR_REMAP) &&
+                                       info.index == vdev->msix_bar) {
                                        ret = msix_sparse_mmap_cap(vdev, &caps);
                                        if (ret)
                                                return ret;
                                }
                        }
-
                        break;
                case VFIO_PCI_ROM_REGION_INDEX:
                {
@@ -1029,7 +1030,8 @@ static int vfio_pci_mmap(void *device_data, struct 
vm_area_struct *vma)
        if (phys_len < PAGE_SIZE || req_start + req_len > phys_len)
                return -EINVAL;
 
-       if (index == vdev->msix_bar) {
+       if (!iommu_capable(pdev->dev.bus, IOMMU_CAP_INTR_REMAP) &&
+               index == vdev->msix_bar) {
                /*
                 * 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 5ffd1d9..1c46c29 100644
--- a/drivers/vfio/pci/vfio_pci_rdwr.c
+++ b/drivers/vfio/pci/vfio_pci_rdwr.c
@@ -18,6 +18,7 @@
 #include <linux/uaccess.h>
 #include <linux/io.h>
 #include <linux/vgaarb.h>
+#include <linux/iommu.h>
 
 #include "vfio_pci_private.h"
 
@@ -164,7 +165,8 @@ 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 (!iommu_capable(pdev->dev.bus, IOMMU_CAP_INTR_REMAP) &&
+               bar == vdev->msix_bar) {
                x_start = vdev->msix_offset;
                x_end = vdev->msix_offset + vdev->msix_size;
        }
-- 
1.7.9.5

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