[Qemu-devel] [PATCH] vfio: check if host device supports INTx

[Frank Blaschka <blaschka@linux.vnet.ibm.com>]

From: Frank Blaschka <frank.blaschka@de.ibm.com>

Let the kernel announce if INTx is available. Yes, there are platforms
(e.g. s390) which do not support INTx.

Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
---
 hw/misc/vfio.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
index d66f3d2..3e9600b 100644
--- a/hw/misc/vfio.c
+++ b/hw/misc/vfio.c
@@ -109,6 +109,7 @@ typedef struct VFIOVGA {
 } VFIOVGA;
 
 typedef struct VFIOINTx {
+    bool available; /* intx available */
     bool pending; /* interrupt pending */
     bool kvm_accel; /* set when QEMU bypass through KVM enabled */
     uint8_t pin; /* which pin to pull for qemu_set_irq */
@@ -554,7 +555,7 @@ static int vfio_enable_intx(VFIODevice *vdev)
     struct vfio_irq_set *irq_set;
     int32_t *pfd;
 
-    if (!pin) {
+    if (!pin || !vdev->intx.available) {
         return 0;
     }
 
@@ -4032,6 +4033,21 @@ static int vfio_get_device(VFIOGroup *group, const char *name, VFIODevice *vdev)
                      vdev->host.function);
     }
 
+    irq_info.index = VFIO_PCI_INTX_IRQ_INDEX;
+    ret = ioctl(vdev->fd, VFIO_DEVICE_GET_IRQ_INFO, &irq_info);
+    if (ret) {
+        /*
+         * This can fail for an old kernel or legacy PCI dev
+         * we assume intx is available
+         */
+        vdev->intx.available = true;
+        ret = 0;
+    } else if (irq_info.count == 0) {
+        vdev->intx.available = false;
+    } else {
+        vdev->intx.available = true;
+    }
+
 error:
     if (ret) {
         QLIST_REMOVE(vdev, next);
-- 
1.8.5.5