vhost: Don't set vring call if guest notifier is unused

The vring call fd is set even when the guest does not use MSI-X (e.g., in the
case of virtio PMD), leading to unnecessary CPU overhead for processing
interrupts.

The commit 96a3d98d2c("vhost: don't set vring call if no vector") optimized the
case where MSI-X is enabled but the queue vector is unset. However, there's an
additional case where the guest uses INTx and the INTx_DISABLED bit in the PCI
config is set, meaning that no interrupt notifier will actually be used.

In such cases, the vring call fd should also be cleared to avoid redundant
interrupt handling.

Fixes: 96a3d98d2c("vhost: don't set vring call if no vector")

Reported-by: Zhiyuan Yuan <yuanzhiyuan@chinatelecom.cn>
Signed-off-by: Jidong Xia <xiajd@chinatelecom.cn>
Signed-off-by: Huaitong Han <hanht2@chinatelecom.cn>
Message-Id: <20250522100548.212740-1-hanht2@chinatelecom.cn>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index c6b5768f3a..9b4bf48439 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -1730,7 +1730,7 @@ static void pci_update_mappings(PCIDevice *d)
     pci_update_vga(d);
 }
 
-static inline int pci_irq_disabled(PCIDevice *d)
+int pci_irq_disabled(PCIDevice *d)
 {
     return pci_get_word(d->config + PCI_COMMAND) & PCI_COMMAND_INTX_DISABLE;
 }