[Qemu-devel] [PATCH] xen/pass-through: fold host PCI command register writes

["Jan Beulich" <JBeulich@suse.com>]

The code introduced to address XSA-126 allows simplification of other
code in xen_pt_initfn(): All we need to do is update "cmd" suitably,
as it'll be written back to the host register near the end of the
function anyway.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/hw/xen/xen_pt.c
+++ b/hw/xen/xen_pt.c
@@ -698,10 +698,7 @@ static int xen_pt_initfn(PCIDevice *d)
                    machine_irq, pirq, rc);
 
         /* Disable PCI intx assertion (turn on bit10 of devctl) */
-        xen_host_pci_set_word(&s->real_device,
-                              PCI_COMMAND,
-                              pci_get_word(s->dev.config + PCI_COMMAND)
-                              | PCI_COMMAND_INTX_DISABLE);
+        cmd |= PCI_COMMAND_INTX_DISABLE;
         machine_irq = 0;
         s->machine_irq = 0;
     } else {
@@ -723,9 +720,7 @@ static int xen_pt_initfn(PCIDevice *d)
                        e_intx, rc);
 
             /* Disable PCI intx assertion (turn on bit10 of devctl) */
-            xen_host_pci_set_word(&s->real_device, PCI_COMMAND,
-                                  *(uint16_t *)(&s->dev.config[PCI_COMMAND])
-                                  | PCI_COMMAND_INTX_DISABLE);
+            cmd |= PCI_COMMAND_INTX_DISABLE;
             xen_pt_mapped_machine_irq[machine_irq]--;
 
             if (xen_pt_mapped_machine_irq[machine_irq] == 0) {