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[Xen-devel] [PATCH] qemu-xen: if pirq == 0 fall back to emulated MSIs



If the pirq requested is 0, it probably means that the guest is
misconfigured, so fall back to the emulated code path.

This patch depends on "qemu-xen: support PV on HVM MSIX remapping" that
is currently not applied.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

diff --git a/hw/pt-msi.c b/hw/pt-msi.c
index b01744e..71fa6f0 100644
--- a/hw/pt-msi.c
+++ b/hw/pt-msi.c
@@ -79,7 +79,12 @@ int pt_msi_setup(struct pt_dev *dev)
          * is passed as dest_id */
         pirq = (dev->msi->addr_hi & 0xffffff00) |
                ((dev->msi->addr_lo >> MSI_TARGET_CPU_SHIFT) & 0xff);
-        PT_LOG("pt_msi_setup requested pirq = %d\n", pirq);
+        if (!pirq)
+            /* this probably identifies an misconfiguration of the guest,
+             * try the emulated path */
+            pirq = -1;
+        else
+            PT_LOG("pt_msi_setup requested pirq = %d\n", pirq);
     }
 
     if ( xc_physdev_map_pirq_msi(xc_handle, domid, AUTO_ASSIGN, &pirq,
@@ -305,7 +310,12 @@ static int pt_msix_update_one(struct pt_dev *dev, int 
entry_nr)
          * is passed as dest_id */
         pirq = ((gaddr >> 32) & 0xffffff00) |
                (((gaddr & 0xffffffff) >> MSI_TARGET_CPU_SHIFT) & 0xff);
-        PT_LOG("pt_msix_update_one requested pirq = %d\n", pirq);
+        if (!pirq)
+            /* this probably identifies an misconfiguration of the guest,
+             * try the emulated path */
+            pirq = -1;
+        else
+            PT_LOG("pt_msix_update_one requested pirq = %d\n", pirq);
     }
 
     /* Check if this entry is already mapped */

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