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authorArthur Hanson Rasmusson <arthur@vgpu.io>2026-10-24 18:23:09 -0400
committerArthur Hanson Rasmusson <arthur@vgpu.io>2026-10-24 18:23:09 -0400
commit4fa7c63b318a5fb7521d1ac82a14a64f666ab4c0 (patch)
tree1fd96b51e79cf7ee8411ae3e42064725a5bbc191 /wiki/open-iov.org/index.php?title=Virtualization_Fundamentals&action=history.html
parentfd5ec7e712408c031620271de8ccf88974eebaa2 (diff)
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vgsp-sema r633: park a held GR launch's push-level release records and deliver them on the eventual forward (the r632 mail hang), gate synthetic shadow pages on an anchored span with per-episode budgets (the r632 junk-candidate flood), and name the release0 redirect cause
The r632 first boot's mail client spun forever in cudaDeviceSynchronize after its vadd launch: the push-level tracking release (0x20480fff0 pay=112) never landed while the client's word stayed at 111, even though the launch itself completed (GUEST GR LAUNCH OK) and its QMD release was software-applied. Root cause: the release records (svc_fwd_rel[]) are per-decode state (reset at the top of svc_decode_stream), and the two GR hold paths (busy-defer hold, m150 data-stalled hold) break out of the pump entry loop BEFORE the release block (hold-engage / inline apply) runs - so a held launch's records are dropped at the pass boundary. The eventual forward (queued from the capture ring at the defer cap, without a re-decode of the entry) then engaged the release hold with whatever records that pass happened to carry (often none, or another entry's). Live evidence: read_proc_va on the spinning client - 0x20480fff0 = 111 (payload 112 never applied), 0x204827f74 = 6 (QMD release delivered); host log - no sema-sw line for 0x20480fff0 val=0x70 anywhere. Fix (parked releases, keyed by vgpu/channel/push VA): both hold paths park the pass's records (svc_grpark_put) before their break; svc_gr_request restores the queued push's parked set into svc_fwd_rel[] at the consume point so the pump's hold-engage holds exactly those records; the two fail-closed REFUSED paths deliver the parked set inline; the session flush clears the table. Bounded log line "GR parked releases restored" (32/boot). Proven live: r633 first boot restored push=0x20043c1c8 n=1 va0=0x20480fff0 pay0=100; r633 mail now completes (VADD bad=0 checksum=12204516.000000, STATUS OK) on two consecutive fresh boots. Also r633: the r632 synthetic shadow caps were per-FILL-CALL and the fill re-runs on every retry pass, so one probe=none junk argument candidate could mint another 1024 synthetic pages per pass - the 8192-page shadow table filled within seconds of the r632 first launch (va-shadow 8192/8192, all synthetic, from the two 16 MB guessed spans of candidates no resolver ever answered), which then killed the lane for every later real page ("shadow table full ... write dropped"). Two changes: - ANCHOR GATE: a synthetic page is created only when the candidate's span already has >= 1 page answered by ipin/resolve/ledger. Existing H2D shadow content still serves unconditionally (the red-draw chain), and a real buffer's unresolved tail stays anchored by its resolved head. A candidate whose every page is answerless takes the historical drop path - its guessed span is not a buffer; - PER-EPISODE BUDGETS: the per-candidate (1024) and per-launch (4096) caps now persist per (push VA, span base) across the episode's passes, not per call. Measured r633: shadow table peak 2048/8192 (vs 8192/8192 full), 32 synthetic pages for the mail launch (vs 4041 junk-inflated n_data), the lane stays available for content serves. Diagnostics (bounded, one boot of evidence): "vgsp-work: gr-rel0 ..." names the release0 resolution chain (rel_pa/ap/hpa/word/pay/unobs) and "vgsp-gr: qmd-rel redirect: ..." names the backend redirect cause. The first live reading answers the release-target question: rel_hpa resolves (0x2fc495000), map_ret=0, unobs=0 - the redirect is the deliberate gsp_phys_rmcall_gr_rel_mod=1 default (m64 forced module-semaphore release), not a resolver failure. The r632 hang was the push-level release loss, fixed above. Build clean (kernel + r65535 warnings only).
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