From db20a3f422ca948784aa74375d1977b7d0a1c7ed Mon Sep 17 00:00:00 2001 From: Cornelia Huck Date: Tue, 15 May 2018 07:33:45 +0000 Subject: s390x/css: disabled subchannels cannot be status pending The 3270 code will try to post an attention interrupt when the 3270 emulator (e.g. x3270) attaches. If the guest has not yet enabled the subchannel for the 3270 device, we will present a spurious cc 1 (status pending) when it uses msch on it later on, e.g. when trying to enable the subchannel. To fix this, just don't do anything in css_conditional_io_interrupt() if the subchannel is not enabled. The 3270 code will work fine with that, and the other user of this function (virtio-ccw) never attempts to post an interrupt for a disabled device to begin with. CC: qemu-stable@nongnu.org Reported-by: Thomas Huth Tested-by: Thomas Huth Acked-by: Christian Borntraeger Acked-by: Halil Pasic Reviewed-by: David Hildenbrand Signed-off-by: Cornelia Huck (cherry picked from commit 6e9c893ecd00afd5344c35d0d0ded50eaa0938f6) --- hw/s390x/css.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/hw/s390x/css.c b/hw/s390x/css.c index 301bf17..56c3fa8 100644 --- a/hw/s390x/css.c +++ b/hw/s390x/css.c @@ -617,6 +617,14 @@ void css_inject_io_interrupt(SubchDev *sch) void css_conditional_io_interrupt(SubchDev *sch) { /* + * If the subchannel is not enabled, it is not made status pending + * (see PoP p. 16-17, "Status Control"). + */ + if (!(sch->curr_status.pmcw.flags & PMCW_FLAGS_MASK_ENA)) { + return; + } + + /* * If the subchannel is not currently status pending, make it pending * with alert status. */ -- 1.8.3.1