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, 4 insertions, 3 deletions

diff --git a/hw/ppc/spapr_vio.c b/hw/ppc/spapr_vio.c
index ac6666a..0f61a55 100644
--- a/hw/ppc/spapr_vio.c
+++ b/hw/ppc/spapr_vio.c
@@ -431,6 +431,7 @@ static void spapr_vio_busdev_realize(DeviceState *qdev, Error **errp)
     VIOsPAPRDevice *dev = (VIOsPAPRDevice *)qdev;
     VIOsPAPRDeviceClass *pc = VIO_SPAPR_DEVICE_GET_CLASS(dev);
     char *id;
+    Error *local_err = NULL;
 
     if (dev->reg != -1) {
         /*
@@ -463,9 +464,9 @@ static void spapr_vio_busdev_realize(DeviceState *qdev, Error **errp)
         dev->qdev.id = id;
     }
 
-    dev->irq = xics_alloc(spapr->icp, 0, dev->irq, false);
-    if (!dev->irq) {
-        error_setg(errp, "can't allocate IRQ");
+    dev->irq = xics_alloc(spapr->icp, 0, dev->irq, false, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
         return;
     }