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>

hw/intc/xics.c

@@ -712,22 +712,22 @@ static int ics_find_free_block(ICSState *ics, int num, int alignnum)
     return -1;
 }
 
-int xics_alloc(XICSState *icp, int src, int irq_hint, bool lsi)
+int xics_alloc(XICSState *icp, int src, int irq_hint, bool lsi, Error **errp)
 {
     ICSState *ics = &icp->ics[src];
     int irq;
 
     if (irq_hint) {
         assert(src == xics_find_source(icp, irq_hint));
         if (!ICS_IRQ_FREE(ics, irq_hint - ics->offset)) {
-            trace_xics_alloc_failed_hint(src, irq_hint);
+            error_setg(errp, "can't allocate IRQ %d: already in use", irq_hint);
             return -1;
         }
         irq = irq_hint;
     } else {
         irq = ics_find_free_block(ics, 1, 1);
         if (irq < 0) {
-            trace_xics_alloc_failed_no_left(src);
+            error_setg(errp, "can't allocate IRQ: no IRQ left");
             return -1;
         }
         irq += ics->offset;
@@ -743,7 +743,8 @@ int xics_alloc(XICSState *icp, int src, int irq_hint, bool lsi)
  * Allocate block of consecutive IRQs, and return the number of the first IRQ in the block.
  * If align==true, aligns the first IRQ number to num.
  */
-int xics_alloc_block(XICSState *icp, int src, int num, bool lsi, bool align)
+int xics_alloc_block(XICSState *icp, int src, int num, bool lsi, bool align,
+                     Error **errp)
 {
     int i, first = -1;
     ICSState *ics = &icp->ics[src];
@@ -763,6 +764,10 @@ int xics_alloc_block(XICSState *icp, int src, int num, bool lsi, bool align)
     } else {
         first = ics_find_free_block(ics, num, 1);
     }
+    if (first < 0) {
+        error_setg(errp, "can't find a free %d-IRQ block", num);
+        return -1;
+    }
 
     if (first >= 0) {
         for (i = first; i < first + num; ++i) {

hw/ppc/spapr_events.c

@@ -588,7 +588,8 @@ static void event_scan(PowerPCCPU *cpu, sPAPRMachineState *spapr,
 void spapr_events_init(sPAPRMachineState *spapr)
 {
     QTAILQ_INIT(&spapr->pending_events);
-    spapr->check_exception_irq = xics_alloc(spapr->icp, 0, 0, false);
+    spapr->check_exception_irq = xics_alloc(spapr->icp, 0, 0, false,
+                                            &error_fatal);
     spapr->epow_notifier.notify = spapr_powerdown_req;
     qemu_register_powerdown_notifier(&spapr->epow_notifier);
     spapr_rtas_register(RTAS_CHECK_EXCEPTION, "check-exception",

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;
         }
 

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;
     }
 

include/hw/ppc/xics.h

@@ -161,8 +161,9 @@ struct ICSIRQState {
 
 qemu_irq xics_get_qirq(XICSState *icp, int irq);
 void xics_set_irq_type(XICSState *icp, int irq, bool lsi);
-int xics_alloc(XICSState *icp, int src, int irq_hint, bool lsi);
-int xics_alloc_block(XICSState *icp, int src, int num, bool lsi, bool align);
+int xics_alloc(XICSState *icp, int src, int irq_hint, bool lsi, Error **errp);
+int xics_alloc_block(XICSState *icp, int src, int num, bool lsi, bool align,
+                     Error **errp);
 void xics_free(XICSState *icp, int irq, int num);
 
 void xics_cpu_setup(XICSState *icp, PowerPCCPU *cpu);

trace-events

@@ -1409,8 +1409,6 @@ xics_ics_write_xive(int nr, int srcno, int server, uint8_t priority) "ics_write_
 xics_ics_reject(int nr, int srcno) "reject irq %#x [src %d]"
 xics_ics_eoi(int nr) "ics_eoi: irq %#x"
 xics_alloc(int src, int irq) "source#%d, irq %d"
-xics_alloc_failed_hint(int src, int irq) "source#%d, irq %d is already in use"
-xics_alloc_failed_no_left(int src) "source#%d, no irq left"
 xics_alloc_block(int src, int first, int num, bool lsi, int align) "source#%d, first irq %d, %d irqs, lsi=%d, alignnum %d"
 xics_ics_free(int src, int irq, int num) "Source#%d, first irq %d, %d irqs"
 xics_ics_free_warn(int src, int irq) "Source#%d, irq %d is already free"