QEMU

  1. Bug #1722884
  2. Comment #2

Comment 2 for bug 1722884

Revision history for this message
Geoffrey McRae (gnif) wrote :

Further to this, it appears to be a race condition with reading from the i8042 controller. I have turned on debugging of PS2 and KBD and filtered out the event that causes the issue. I have split the below up to show the valid reads for the mouse and then the sequence that triggers a reset when the keyboard is used.

KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x08
KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x00
KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x02
KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x00

KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x18
KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0xfe
KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x02
KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x00

KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x08
KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x00
KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x01
KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x00

KBD: kbd: read status=0x3d
KBD: kbd: read status=0x1d <-- the status changed on the 2nd call.
KBD: kbd: read status=0x1d
KBD: kbd: read data=0x9e

KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x18
KBD: kbd: read data=0xff <-- two data reads without checking status
KBD: kbd: read status=0x3d <-- guest looking for mouse movements
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x02 <-- first byte
KBD: kbd: read status=0x3d
KBD: kbd: read status=0x3d
KBD: kbd: read data=0x00 <-- 2nd byte
KBD: kbd: read status=0x1c <-- no more data, there should be two more bytes
KBD: kbd: read status=0x1c
KBD: kbd: read status=0x1c

here the host attempts to reset the device

KBD: kbd: write cmd=0xd4 <-- write to mouse cmd
KBD: kbd: read status=0x1c
KBD: kbd: read status=0x1c
KBD: kbd: read status=0x1c
KBD: kbd: write data=0xff <-- reset mouse
kbd: write mouse 0xff