xics: report errors with the QEMU Error API

Using the return value to report errors is error prone:
- xics_alloc() returns -1 on error but spapr_vio_busdev_realize() errors
  on 0
- xics_alloc_block() returns the unclear value of ics->offset - 1 on error
  but both rtas_ibm_change_msi() and spapr_phb_realize() error on 0

This patch adds an errp argument to xics_alloc() and xics_alloc_block() to
report errors. The return value of these functions is a valid IRQ number
if errp is NULL. It is undefined otherwise.

The corresponding error traces get promotted to error messages. Note that
the "can't allocate IRQ" error message in spapr_vio_busdev_realize() also
moves to xics_alloc(). Similar error message consolidation isn't really
applicable to xics_alloc_block() because callers have extra context (device
config address, MSI or MSIX).

This fixes the issues mentioned above.

Based on previous work from Brian W. Hart.

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 10 insertions, 6 deletions

diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index 9b2b546b54..e8edad3ab7 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -280,6 +280,7 @@ static void rtas_ibm_change_msi(PowerPCCPU *cpu, sPAPRMachineState *spapr,
     PCIDevice *pdev = NULL;
     spapr_pci_msi *msi;
     int *config_addr_key;
+    Error *err = NULL;
 
     switch (func) {
     case RTAS_CHANGE_MSI_FN:
@@ -354,9 +355,10 @@ static void rtas_ibm_change_msi(PowerPCCPU *cpu, sPAPRMachineState *spapr,
 
     /* Allocate MSIs */
     irq = xics_alloc_block(spapr->icp, 0, req_num, false,
-                           ret_intr_type == RTAS_TYPE_MSI);
-    if (!irq) {
-        error_report("Cannot allocate MSIs for device %x", config_addr);
+                           ret_intr_type == RTAS_TYPE_MSI, &err);
+    if (err) {
+        error_reportf_err(err, "Can't allocate MSIs for device %x: ",
+                          config_addr);
         rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
         return;
     }
@@ -1367,10 +1369,12 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
     /* Initialize the LSI table */
     for (i = 0; i < PCI_NUM_PINS; i++) {
         uint32_t irq;
+        Error *local_err = NULL;
 
-        irq = xics_alloc_block(spapr->icp, 0, 1, true, false);
-        if (!irq) {
-            error_setg(errp, "spapr_allocate_lsi failed");
+        irq = xics_alloc_block(spapr->icp, 0, 1, true, false, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            error_prepend(errp, "can't allocate LSIs: ");
             return;
         }