vgsp: aperture-aware foreign USERD guard and wire fallback

c24 (V30) skipped the X/GLX channel's own sysmem USERD block because the
same numeric PA 0x8f0000 is owned by the RC watchdog channel in vidmem;
the X server then failed with 'Failed to initialize DMA' and 'Failed to
allocate push buffer'.  Compare the aperture as well as the page, and keep
base 0 + userdOffset as a fallback when the client memory-object table
cannot name the USERD (the resolver still wins when it has a verified
object).  This restores the c23 X bring-up while keeping the fail-closed
table path.

Validation pending a fresh V31 cycle: X starts, glxinfo/glxgears, chan_dump
userd page/aper, and the USERD resolution/fallback witness lines.

0 files changed, 0 insertions, 0 deletions