[PATCH for-5.2] spapr: Simplify error handling in spapr_phb_realize()

[Greg Kurz]

The spapr_phb_realize() function has a local_err variable which
is used to:

1) check failures of spapr_irq_findone() and spapr_irq_claim()

2) prepend extra information to the error message

Recent work from Markus Armbruster highlighted we get better
code when testing the return value of a function, rather than
setting up all the local_err boiler plate. For similar reasons,
it is now preferred to use ERRP_GUARD() and error_prepend()
rather than error_propagate_prepend().

Since spapr_irq_findone() and spapr_irq_claim() return negative
values in case of failure, do both changes.

This is just cleanup, no functional impact.

Signed-off-by: Greg Kurz <groug@kaod.org>
---

Since we add ERRP_GUARD(), we could theoretically check *errp
rather than the return value, and thus avoid the uint32_t to
int32_t change but I personally find it clearer the other way.
---
 hw/ppc/spapr_pci.c |   16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index 21681215d405..b1ce51327db4 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -1796,6 +1796,7 @@ static void spapr_phb_destroy_msi(gpointer opaque)
 
 static void spapr_phb_realize(DeviceState *dev, Error **errp)
 {
+    ERRP_GUARD();
     /* We don't use SPAPR_MACHINE() in order to exit gracefully if the user
      * tries to add a sPAPR PHB to a non-pseries machine.
      */
@@ -1813,7 +1814,6 @@ static void spapr_phb_realize(DeviceState *dev, Error 
**errp)
     uint64_t msi_window_size = 4096;
     SpaprTceTable *tcet;
     const unsigned windows_supported = spapr_phb_windows_supported(sphb);
-    Error *local_err = NULL;
 
     if (!spapr) {
         error_setg(errp, TYPE_SPAPR_PCI_HOST_BRIDGE " needs a pseries 
machine");
@@ -1964,13 +1964,12 @@ static void spapr_phb_realize(DeviceState *dev, Error 
**errp)
 
     /* Initialize the LSI table */
     for (i = 0; i < PCI_NUM_PINS; i++) {
-        uint32_t irq = SPAPR_IRQ_PCI_LSI + sphb->index * PCI_NUM_PINS + i;
+        int32_t irq = SPAPR_IRQ_PCI_LSI + sphb->index * PCI_NUM_PINS + i;
 
         if (smc->legacy_irq_allocation) {
-            irq = spapr_irq_findone(spapr, &local_err);
-            if (local_err) {
-                error_propagate_prepend(errp, local_err,
-                                        "can't allocate LSIs: ");
+            irq = spapr_irq_findone(spapr, errp);
+            if (irq < 0) {
+                error_prepend(errp, "can't allocate LSIs: ");
                 /*
                  * Older machines will never support PHB hotplug, ie, this is 
an
                  * init only path and QEMU will terminate. No need to rollback.
@@ -1979,9 +1978,8 @@ static void spapr_phb_realize(DeviceState *dev, Error 
**errp)
             }
         }
 
-        spapr_irq_claim(spapr, irq, true, &local_err);
-        if (local_err) {
-            error_propagate_prepend(errp, local_err, "can't allocate LSIs: ");
+        if (spapr_irq_claim(spapr, irq, true, errp) < 0) {
+            error_prepend(errp, "can't allocate LSIs: ");
             goto unrealize;
         }