A thread that sceKernelRaiseException redirects resumes through
RtlRestoreContext with a CONTEXT that has no XSTATE, so the upper halves
of ymm0-ymm15 came back as the handler and the delivery path left them.
A handler or host routine that runs vzeroupper or any VEX instruction
(Zen 2 guest code, the CRT's memcpy) cleared the upper lanes of a thread
interrupted in the middle of AVX code. The entry stub now stores
ymm0-ymm15 next to the delivery when the CPU and the OS enable AVX, and
the exit loads them back right before RtlRestoreContext, which restores
only the low halves.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HeC9bA3n74TzJRYv9AgBE8
15c1962e82