spapr_pci: Fix config space corruption

When disabling MSI/MSIX via "ibm,change-msi" RTAS call, no check was made
if MSI or MSIX is actually supported and the MSI message was reset
unconditionally. If this happened on a device which does not support MSI
(but does support MSIX, otherwise "ibm,change-msi" would not be called),
this device would have PCIDevice::msi_cap field (MSI capability offset)
set to zero and writing a vector would actually clear PCI status.

This clears MSI message only if MSI or MSIX is present on a device.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Alexander Graf <agraf@suse.de>

hw/ppc/spapr_pci.c

@@ -262,7 +262,6 @@ static void rtas_ibm_change_msi(PowerPCCPU *cpu, sPAPREnvironment *spapr,
     unsigned int irq, max_irqs = 0, num = 0;
     sPAPRPHBState *phb = NULL;
     PCIDevice *pdev = NULL;
-    bool msix = false;
     spapr_pci_msi *msi;
     int *config_addr_key;
 
@@ -300,7 +299,12 @@ static void rtas_ibm_change_msi(PowerPCCPU *cpu, sPAPREnvironment *spapr,
         }
 
         xics_free(spapr->icp, msi->first_irq, msi->num);
-        spapr_msi_setmsg(pdev, 0, msix, 0, num);
+        if (msi_present(pdev)) {
+            spapr_msi_setmsg(pdev, 0, false, 0, num);
+        }
+        if (msix_present(pdev)) {
+            spapr_msi_setmsg(pdev, 0, true, 0, num);
+        }
         g_hash_table_remove(phb->msi, &config_addr);
 
         trace_spapr_pci_msi("Released MSIs", config_addr);