Open-IOV vGPU-IO: host-side GSP emulation for unmodified NVIDIA guest drivers https://git.vgpu.io/open-iov.git/atom?h=master 2026-10-21T18:02:15+00:00 2026-10-21T18:02:15+00:00 Arthur Hanson Rasmusson arthur@vgpu.io 2026-10-21T18:02:15+00:00 urn:sha1:393f1c676d0fc9c7b37ab6a52efe7e2d288d7e90 With gsp_phys_rmcall_gr_rel_mod=1 (release0 -> module semaphore, the ordering fix for the engine-release-before-copy-out race) the engine never writes the guest's own QMD release word, so the host must author it on EVERY backend outcome. The hold's success/fail edges do; a launch with no deferred release records (no hold engaged) fell through and its client hung on a word nothing would ever write - the r414 saxpy f0 cur=5 stall. The backend now reports qmd_rel_redirected in the copy result whenever it points release0 at the module semaphore (rel_mod, or no targetable guest release page). svc_fwd_gr_work folds that into the existing gr_rel_unobserved latch, which makes the bounded outcome check author the word on done (success or failure) - the same forward-only write the hold edges perform. rel_mod=0 paths are unchanged (the engine still authors the word and the latch is only set on an unresolved release page).