[Qemu-devel] [PATCH] virtio-pci: report an error when disable msix

[Amos Kong <akong@redhat.com>]

QEMU remains 4k memory for PCI BAR, each msix entry takes 16 bytes.
If user assigns more than 128 vectors, msix resource isn't enough,
so msix will be disabled.

This patch addes a note when fail to init exclusive bars for msix.

 qemu -device virtio-net-pci,netdev=h1,vectors=129,mq=on \
      -netdev tap,id=h1,queues=8

Signed-off-by: Amos Kong <akong@redhat.com>
---
 hw/virtio/virtio-pci.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index ce97514..ea5dcdf 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -976,6 +976,8 @@ static void virtio_pci_device_plugged(DeviceState *d)
 
     if (proxy->nvectors &&
         msix_init_exclusive_bar(&proxy->pci_dev, proxy->nvectors, 1)) {
+        error_report("%s: unable to init exclusive bars for msix, disable msix",
+                     __func__);
         proxy->nvectors = 0;
     }
 
-- 
1.9.0