[Qemu-devel] [PATCH 3/4] pci: interrupt status bit implementation

["Michael S. Tsirkin" <mst@redhat.com>]

interrupt status is a mandatory feature in PCI spec,
so devices must implement it to be spec compliant.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/pci.c |   22 ++++++++++++++++++++++
 hw/pci.h |    1 +
 2 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/hw/pci.c b/hw/pci.c
index 7717461..844664b 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -103,12 +103,24 @@ static int pci_bar(PCIDevice *d, int reg)
     return type == PCI_HEADER_TYPE_BRIDGE ? PCI_ROM_ADDRESS1 : PCI_ROM_ADDRESS;
 }
 
+/* Update interrupt status bit in config space on interrupt
+ * state change. */
+static void pci_update_irq_status(PCIDevice *dev)
+{
+    if (dev->irq_status) {
+        dev->config[PCI_STATUS] |= PCI_STATUS_INTERRUPT;
+    } else {
+        dev->config[PCI_STATUS] &= ~PCI_STATUS_INTERRUPT;
+    }
+}
+
 static void pci_device_reset(PCIDevice *dev)
 {
     int r;
 
     memset(dev->irq_state, 0, sizeof dev->irq_state);
     dev->irq_status = 0;
+    pci_update_irq_status(dev);
     dev->config[PCI_COMMAND] &= ~(PCI_COMMAND_IO | PCI_COMMAND_MEMORY |
                                   PCI_COMMAND_MASTER);
     dev->config[PCI_CACHE_LINE_SIZE] = 0x0;
@@ -314,7 +326,14 @@ static inline const VMStateDescription *pci_get_vmstate(PCIDevice *s)
 
 void pci_device_save(PCIDevice *s, QEMUFile *f)
 {
+    /* Clear interrupt status bit: it is implicit
+     * in irq_state which we are saving.
+     * This makes us compatible with old devices
+     * which never set or clear this bit. */
+    s->config[PCI_STATUS] &= ~PCI_STATUS_INTERRUPT;
     vmstate_save_state(f, pci_get_vmstate(s), s);
+    /* Restore the interrupt status bit. */
+    pci_update_irq_status(s);
 }
 
 int pci_device_load(PCIDevice *s, QEMUFile *f)
@@ -324,6 +343,8 @@ int pci_device_load(PCIDevice *s, QEMUFile *f)
     for (i = 0; i < ARRAY_SIZE(s->irq_state); ++i) {
         s->irq_status += s->irq_state[i];
     }
+    /* Restore the interrupt status bit. */
+    pci_update_irq_status(s);
     return ret;
 }
 
@@ -914,6 +935,7 @@ static void pci_set_irq(void *opaque, int irq_num, int level)
 
     pci_dev->irq_state[irq_num] = level;
     pci_dev->irq_status += change;
+    pci_update_irq_status(s);
     pci_change_irq_level(pci_dev, irq_num, change);
 }
 
diff --git a/hw/pci.h b/hw/pci.h
index 2e172f6..c3f2c3f 100644
--- a/hw/pci.h
+++ b/hw/pci.h
@@ -102,6 +102,7 @@ typedef struct PCIIORegion {
 #define  PCI_COMMAND_MEMORY	0x2	/* Enable response in Memory space */
 #define  PCI_COMMAND_MASTER	0x4	/* Enable bus master */
 #define PCI_STATUS              0x06    /* 16 bits */
+#define  PCI_STATUS_INTERRUPT   0x08
 #define PCI_REVISION_ID         0x08    /* 8 bits  */
 #define PCI_CLASS_PROG		0x09	/* Reg. Level Programming Interface */
 #define PCI_CLASS_DEVICE        0x0a    /* Device class */
-- 
1.6.5.2.143.g8cc62