VT-d: relax source qualifier for MSI of phantom functions

With ordinary requests allowed to come from phantom functions, the
remapping tables ought to be set up to allow for MSI triggers to come
from other than the "real" device too.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>

--- a/xen/drivers/passthrough/vtd/intremap.c
+++ b/xen/drivers/passthrough/vtd/intremap.c
@@ -442,13 +442,22 @@ static void set_msi_source_id(struct pci
     devfn = pdev->devfn;
     switch ( pdev->type )
     {
+        unsigned int sq;
+
     case DEV_TYPE_PCIe_BRIDGE:
     case DEV_TYPE_PCIe2PCI_BRIDGE:
     case DEV_TYPE_LEGACY_PCI_BRIDGE:
         break;
 
     case DEV_TYPE_PCIe_ENDPOINT:
-        set_ire_sid(ire, SVT_VERIFY_SID_SQ, SQ_ALL_16, PCI_BDF2(bus, devfn));
+        switch ( pdev->phantom_stride )
+        {
+        case 1: sq = SQ_13_IGNORE_3; break;
+        case 2: sq = SQ_13_IGNORE_2; break;
+        case 4: sq = SQ_13_IGNORE_1; break;
+        default: sq = SQ_ALL_16; break;
+        }
+        set_ire_sid(ire, SVT_VERIFY_SID_SQ, sq, PCI_BDF2(bus, devfn));
         break;
 
     case DEV_TYPE_PCI: