[Qemu-devel] [PATCH 5/5] msix: clear pending bit of an unused vector

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

PCI spec states:
if a masked vector has its Pending bit set, and the associated
underlying interrupt events are somehow satisfied (usually by software
though the exact manner is function-specific), the function must clear
the Pending bit, to avoid sending a spurious interrupt message later
when software unmasks the vector.

In our case this happens if vector becomes unused.
Clear pending bit in this case.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/msix.c |   27 +++++++++++++++++----------
 1 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/hw/msix.c b/hw/msix.c
index a60ea95..0baedef 100644
--- a/hw/msix.c
+++ b/hw/msix.c
@@ -108,14 +108,6 @@ static int msix_add_config(struct PCIDevice *pdev, unsigned short nentries,
     return 0;
 }
 
-static void msix_free_irq_entries(PCIDevice *dev)
-{
-    int vector;
-
-    for (vector = 0; vector < dev->msix_entries_nr; ++vector)
-        dev->msix_entry_used[vector] = 0;
-}
-
 static uint32_t msix_mmio_readl(void *opaque, target_phys_addr_t addr)
 {
     PCIDevice *dev = opaque;
@@ -299,6 +291,16 @@ err_index:
     return ret;
 }
 
+static void msix_free_irq_entries(PCIDevice *dev)
+{
+    int vector;
+
+    for (vector = 0; vector < dev->msix_entries_nr; ++vector) {
+        dev->msix_entry_used[vector] = 0;
+        msix_clr_pending(dev, vector);
+    }
+}
+
 /* Clean up resources for the device. */
 int msix_uninit(PCIDevice *dev)
 {
@@ -415,8 +417,13 @@ int msix_vector_use(PCIDevice *dev, unsigned vector)
 /* Mark vector as unused. */
 void msix_vector_unuse(PCIDevice *dev, unsigned vector)
 {
-    if (vector < dev->msix_entries_nr && dev->msix_entry_used[vector])
-        --dev->msix_entry_used[vector];
+    if (vector >= dev->msix_entries_nr || !dev->msix_entry_used[vector]) {
+        return;
+    }
+    if (--dev->msix_entry_used[vector]) {
+        return;
+    }
+    msix_clr_pending(dev, vector);
 }
 
 void msix_unuse_all_vectors(PCIDevice *dev)
-- 
1.6.5.2.143.g8cc62