diff options
Diffstat (limited to 'docs/GSP_EMULATION_ARCHITECTURE.md')
| -rw-r--r-- | docs/GSP_EMULATION_ARCHITECTURE.md | 25 |
1 files changed, 17 insertions, 8 deletions
diff --git a/docs/GSP_EMULATION_ARCHITECTURE.md b/docs/GSP_EMULATION_ARCHITECTURE.md index eb7f697..8da8f49 100644 --- a/docs/GSP_EMULATION_ARCHITECTURE.md +++ b/docs/GSP_EMULATION_ARCHITECTURE.md @@ -116,14 +116,23 @@ implementation** when `gsp_rpc_emulation_is_enabled()` (set once per mdev by > RPC loop plus multi-second stalls. Emulation mode now fails these fast with > `pr_warn_ratelimited`. -### Memory model caveat (design note) - -Guest VRAM (BAR1) is mapped **directly to the host GPU's physical BAR1** (gpa). -`gsp_rpc_alloc_emul`, however, services ALLOC with *host system pages* DMA-mapped -to the physical device. These two models are not yet unified: a guest allocation -returning `gpu_va=0x100000000+` is not visible through the guest's BAR1 window. -This is a known design gap to resolve before CUDA workloads; it does not affect -driver probe/GSP boot, which is the current milestone. +### Memory model (corrected 2026-09-22) + +Guest BAR1 (VRAM aperture) is backed by a **dedicated host-RAM vzalloc buffer** +(256 MB, `bar_init.c`), NOT the host GPU's physical BAR1. Guest VRAM accesses +hit our clean host-RAM backing. This is a placeholder — for real CUDA compute, +the memory model must evolve (see `refactored-architecture.md` Phase 2): + +- **Current (Phase 1)**: Guest VRAM = host RAM (safe, no host GPU corruption). + Guest driver probes but cannot compute. +- **Phase 2**: Guest VRAM backed by DMA-coherent host memory or physical GPU + VRAM partition (required for CUDA). +- **Phase 3**: Guest channel/pushbuffer work forwarded to physical GPU + channels (required for compute). + +Guest BAR3 (instance memory window) is also a **vzalloc'd shadow** (32 MB, +`bar_init.c`), NOT the physical GPU's BAR3. Guest BAR3 writes must not reach +the host GPU's instance memory (root cause of host GSP crash, fixed `85d0668`). --- |