[v5][PATCH 15/16] xen/vtd: prevent from assign the device with shared rmrr

[Tiejun Chen <tiejun.chen@intel.com>]

Currently we're intending to cover this kind of devices
with shared RMRR simply since the case of shared RMRR is
a rare case according to our previous experiences. But
late we can group these devices which shared rmrr, and
then allow all devices within a group to be assigned to
same domain.

CC: Yang Zhang <yang.z.zhang@intel.com>
CC: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>
---
v5:
 
* Nothing is changed.

v4:

* Refine one code comment.

 xen/drivers/passthrough/vtd/iommu.c | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
index c833290..095fb1d 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2297,13 +2297,39 @@ static int intel_iommu_assign_device(
     if ( list_empty(&acpi_drhd_units) )
         return -ENODEV;
 
+    seg = pdev->seg;
+    bus = pdev->bus;
+    /*
+     * In rare cases one given rmrr is shared by multiple devices but
+     * obviously this would put the security of a system at risk. So
+     * we should prevent from this sort of device assignment.
+     *
+     * TODO: in the future we can introduce group device assignment
+     * interface to make sure devices sharing RMRR are assigned to the
+     * same domain together.
+     */
+    for_each_rmrr_device( rmrr, bdf, i )
+    {
+        if ( rmrr->segment == seg &&
+             PCI_BUS(bdf) == bus &&
+             PCI_DEVFN2(bdf) == devfn )
+        {
+            if ( rmrr->scope.devices_cnt > 1 )
+            {
+                printk(XENLOG_G_ERR VTDPREFIX
+                       " cannot assign %04x:%02x:%02x.%u"
+                       " with shared RMRR for Dom%d.\n",
+                       seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn),
+                       d->domain_id);
+                return -EPERM;
+            }
+        }
+    }
+
     ret = reassign_device_ownership(hardware_domain, d, devfn, pdev);
     if ( ret )
         return ret;
 
-    seg = pdev->seg;
-    bus = pdev->bus;
-
     /* Setup rmrr identity mapping */
     for_each_rmrr_device( rmrr, bdf, i )
     {
-- 
1.9.1