hw/misc/edu: support MSI interrupt

So now edu device can support both line or msi interrupt, depending on
how user configures it.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <1475067819-21413-1-git-send-email-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

docs/specs/edu.txt

@@ -52,7 +52,7 @@ size == 8 for the rest.
 
 0x20 (RW) : status register, bitwise OR
 	    0x01 -- computing factorial (RO)
-	    0x80 -- raise interrupt 0x01 after finishing factorial computation
+	    0x80 -- raise interrupt after finishing factorial computation
 
 0x24 (RO) : interrupt status register
 	    It contains values which raised the interrupt (see interrupt raise
@@ -87,6 +87,11 @@ An IRQ is generated when written to the interrupt raise register. The value
 appears in interrupt status register when the interrupt is raised and has to
 be written to the interrupt acknowledge register to lower it.
 
+The device supports both INTx and MSI interrupt. By default, INTx is
+used. Even if the driver disabled INTx and only uses MSI, it still
+needs to update the acknowledge register at the end of the IRQ handler
+routine.
+
 DMA controller
 --------------
 One has to specify, source, destination, size, and start the transfer. One

hw/misc/edu.c

@@ -24,6 +24,7 @@
 
 #include "qemu/osdep.h"
 #include "hw/pci/pci.h"
+#include "hw/pci/msi.h"
 #include "qemu/timer.h"
 #include "qemu/main-loop.h" /* iothread mutex */
 #include "qapi/visitor.h"
@@ -69,11 +70,20 @@ typedef struct {
     uint64_t dma_mask;
 } EduState;
 
+static bool edu_msi_enabled(EduState *edu)
+{
+    return msi_enabled(&edu->pdev);
+}
+
 static void edu_raise_irq(EduState *edu, uint32_t val)
 {
     edu->irq_status |= val;
     if (edu->irq_status) {
-        pci_set_irq(&edu->pdev, 1);
+        if (edu_msi_enabled(edu)) {
+            msi_notify(&edu->pdev, 0);
+        } else {
+            pci_set_irq(&edu->pdev, 1);
+        }
     }
 }
 
@@ -81,7 +91,7 @@ static void edu_lower_irq(EduState *edu, uint32_t val)
 {
     edu->irq_status &= ~val;
 
-    if (!edu->irq_status) {
+    if (!edu->irq_status && !edu_msi_enabled(edu)) {
         pci_set_irq(&edu->pdev, 0);
     }
 }
@@ -342,6 +352,10 @@ static void pci_edu_realize(PCIDevice *pdev, Error **errp)
 
     pci_config_set_interrupt_pin(pci_conf, 1);
 
+    if (msi_init(pdev, 0, 1, true, false, errp)) {
+        return;
+    }
+
     memory_region_init_io(&edu->mmio, OBJECT(edu), &edu_mmio_ops, edu,
                     "edu-mmio", 1 << 20);
     pci_register_bar(pdev, 0, PCI_BASE_ADDRESS_SPACE_MEMORY, &edu->mmio);