On 02/19/2018 09:17 AM, Christian Borntraeger wrote:

On 02/19/2018 03:15 PM, Christian Borntraeger wrote:

On 02/16/2018 11:07 PM, Collin L. Walling wrote:
It is possible while waiting for multiple types of external
interrupts that we might have pending irqs remaining between
irq consumption and irq-type disabling. Those interrupts
could potentially propagate to the guest after IPL completes
and cause unwanted behavior.

As it is today, the SCLP will only recognize write events that
are enabled by the control program's send and receive masks. To
limit the window for, and prevent further irqs from, ASCII
console events (specifically keystrokes), we should only enable
the control program's receive mask when we need it.

As an additional measure, once we've disabled/cleared the control
program's receive mask, we will print an empty string in order
to consume any pending service interrupt.

Signed-off-by: Collin L. Walling <wall...@linux.vnet.ibm.com>
This should work some comments below:

  pc-bios/s390-ccw/menu.c     |  5 +++++
  pc-bios/s390-ccw/s390-ccw.h |  1 +
  pc-bios/s390-ccw/sclp.c     | 10 ++++------
  3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/pc-bios/s390-ccw/menu.c b/pc-bios/s390-ccw/menu.c
index 9601043..14410a8 100644
--- a/pc-bios/s390-ccw/menu.c
+++ b/pc-bios/s390-ccw/menu.c
@@ -11,6 +11,7 @@

  #include "menu.h"
  #include "s390-ccw.h"
+#include "sclp.h"

  #define KEYCODE_NO_INP '\0'
  #define KEYCODE_ESCAPE '\033'
@@ -117,8 +118,12 @@ static int get_index(void)

      memset(buf, 0, sizeof(buf));

      len = read_prompt(buf, sizeof(buf));

+    sclp_set_write_mask(0, SCLP_EVENT_MASK_MSG_ASCII);
+    sclp_print(""); /* Clear any pending service int */
Why cant you use consume_sclp_int from start.S and not do any printing?
Shouldnt sclp_set_write_mask always make an interrupt pending?
In fact sclp_set_write_mask should already call consume_sclp_int. Have you seen 

Correct.  We don't need that print there.  Setting the mask kills two birds with one stone.

- Collin L Walling

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