vgsp-disp: never publish GET past PUT; bounded no-parse push dump

r1630: the window channel's first push read returned unparseable bytes
(0 methods) and the parser walked off the 4 KB ring, publishing
GET=0x1000 while PUT stayed 0x4e4.  nvidia-modeset then wedged in
'Error while waiting for GPU progress', Xorg never started and glxinfo/
GZDoom never reached the GL path.

Only consume a segment that parses exactly to the driver's PUT.  On a
short/invalid read, leave consumed unchanged: the pump retries next
pass (which also covers a ring the guest kicked before its content is
visible) and GET can never move past PUT.  Dump the head of an
unparseable segment (bounded, disp_dbg) to name what the ring holds.
Reset dump budgets per mdev cleanup so each boot keeps its diagnostics.

0 files changed, 0 insertions, 0 deletions