[RFC PATCH v1 2/8] vfio-ccw: Don't inject an I/O interrupt if the subchannel is not enabled

[Eric Farman]

From: Farhan Ali <address@hidden>

According to PoPs, when the SCHIB.PMCW bit 8 is 0 status presented by
the device is not made available to the program. So don't inject an
interrupt in the guest if the guest OS has not enabled the
subchannel.

Signed-off-by: Farhan Ali <address@hidden>
Signed-off-by: Eric Farman <address@hidden>
---

Notes:
    v0->v1: [EF]
     - Update commit message, as the bit in question is bit 8 not 15

 hw/vfio/ccw.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
index 0919ddbeb8..0590a6f512 100644
--- a/hw/vfio/ccw.c
+++ b/hw/vfio/ccw.c
@@ -230,6 +230,11 @@ static void vfio_ccw_io_notifier_handler(void *opaque)
         return;
     }
 
+    /* Virtual subchannel is not enabled */
+    if (!(schib->pmcw.flags & PMCW_FLAGS_MASK_ENA)) {
+        return;
+    }
+
     size = pread(vcdev->vdev.fd, region, vcdev->io_region_size,
                  vcdev->io_region_offset);
     if (size == -1) {
-- 
2.17.1