vfio-ccw: Fix the conversion of Format-0 CCWs to Format-1

When processing Format-0 CCWs, we use the "len" variable as the
number of CCWs to convert to Format-1.  But that variable
contains zero here, and is not a meaningful CCW count until
ccwchain_calc_length() returns.  Since that routine requires and
expects Format-1 CCWs to identify the chaining behavior, the
format conversion must be done first.

Convert the 2KB we copied even if it's more than we need.

Fixes: 7f8e89a8f2fd ("vfio-ccw: Factor out the ccw0-to-ccw1 transition")
Reported-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20190702180928.18113-1-farman@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index a7b9dfd5b4646feee91ec6ed43cc1c42e53a6305..1d4c893ead233bb4f2edef2b0194f33025579d8f 100644 (file)
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -431,7 +431,7 @@ static int ccwchain_handle_ccw(u32 cda, struct channel_program *cp)
 
        /* Convert any Format-0 CCWs to Format-1 */
        if (!cp->orb.cmd.fmt)
-               convert_ccw0_to_ccw1(cp->guest_cp, len);
+               convert_ccw0_to_ccw1(cp->guest_cp, CCWCHAIN_LEN_MAX);
 
        /* Count the CCWs in the current chain */
        len = ccwchain_calc_length(cda, cp);