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Re: [Xen-devel] [v3][PATCH 16/16] xen/vtd: prevent from assign the device with shared rmrr



On 2015/6/17 18:28, Jan Beulich wrote:
On 11.06.15 at 03:15, <tiejun.chen@xxxxxxxxx> wrote:
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2277,13 +2277,37 @@ 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: actually we can group these devices which shared rmrr, and
+     * then allow all devices within a group to be assigned to same domain.
+     */
+    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 )
+            {
+                ret = -EPERM;
+                printk(XENLOG_G_ERR VTDPREFIX
+                       " cannot assign this device with shared RMRR for Dom%d 
(%d)\n",
+                       d->domain_id, ret);
+                return ret;

return -EPERM. No need to assign the value to ret, and no need to
add the constant error code to the log entry. What's missing otoh
is what "this device" is - you should print SBDF instead.


Right.

                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;


Thanks
Tiejun

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