From c3a295efd1b1132bbaa5d422cd05b3fa8e89a8bf Mon Sep 17 00:00:00 2001 From: Arthur Hanson Rasmusson Date: Mon, 21 Sep 2026 13:06:51 -0400 Subject: kernel: Fix GSP emulation shadow binding, eventfd wiring, RPC livelocks + docs suite + repo reorg CRITICAL FIXES (guest driver bring-up): - gsp_emulation.c: emulation engine bound to the WRONG BAR0 - it polled the host physical BAR0 (bars[0].vaddr ioremap) for the doorbell and read RPCs from a local dma_alloc_wc buffer, while the guest writes land in the vzalloc'd bar0_shadow. The RPC path could never work; PBA writes even corrupted the host GPU's physical BAR0+0x3000. gsp_emu_init now binds exclusively to bar0_shadow (doorbell/mailbox/PBA aliases; shared_mem_dma==0 marks the alias so cleanup never dma_free's it). - main.c SET_IRQS: DATA_EVENTFD eventfds were DISCARDED ('TODO' + kfree) - the guest never received MSI-X completions. Full wiring now: eventfd_ctx_fdget per vector, fd -1 clears, dev_close releases refs. gsp_emu_inject_completion_interrupt looks up vgpu->irqs[0].trigger LIVE (init-time copy was permanently NULL since QEMU wires after gsp_emu_init). - gsp_rpc_client.c: BAR_TRAP/MIGRATE in emulation mode called gsp_rpc_submit_raw which rings the SAME doorbell the thread polls - self-triggered RPC livelock + multi-second stalls. Now fail fast with -ENOTSUPP + pr_warn_ratelimited (guest BAR access is direct MMIO). MORE FIXES: - main.c: nv_vgpu_config_write returned SIZE_MAX (while(count--) wrap) and was dead code while the VFIO write handler did unfiltered byte copies (guest could rewrite vendor ID/BARs). Return fixed; VFIO write handler now routes through the per-register filter. - kernel/Makefile: M=$(PWD) used the env var which is stale when invoked via the top-level make (pointed at repo root -> kbuild silently built NOTHING; explains every 'stale .ko' incident). Now M=$(CURDIR). - Warnings sweep: header prototypes for mdev/type functions, format casts in gsp_comm.c DRY-RUN logs, unused variable. ROBUSTNESS (harness/tooling): - vgpu_vm.py: run had no timeout (start could block forever); guest_shell recv could block forever on a wedged guest. Both now bounded; guest_shell pre-flights guest-ping and reports wedge diagnostics. - stack_manager.sh: qemu/qemu-debug now launch via the vgpu_vm.py harness (workflow rule: never raw QEMU). REPO REORGANIZATION: - driver/ (legacy guest-side gsp-vgpu.ko) moved to legacy-driver-guest/ (reference only, not built; README explains). 3 legacy un-buildable test files moved to legacy-driver-guest/kernel-tests/. Top-level Makefile cleaned of the dead DRIVER_DIR reference. DOCUMENTATION SUITE (new): - docs/GSP_EMULATION_ARCHITECTURE.md - emulator deep-dive: shadow BAR0 model, doorbell protocol, dispatch table, MSI-X path, lifecycle, memory- model caveats - docs/DEBUGGING.md - QEMU GDB stub workflow, serial console, QMP NMI, failure taxonomy, full bring-up validation checklist, EPT-livelock case study, version-matrix discipline - docs/ONBOARDING.md - repo tour, coding standards (incl. virt_to_phys / dma_addr_t / get-put rules), first build & test - docs/VERSION_UPGRADE.md - end-to-end new-driver-version procedure (firmware fetch, Ghidra analysis, configs, signatures, validation) - docs/PERFORMANCE.md - bare-metal A/B methodology + targets - README.md doc index; STATE.md refreshed; DEVELOPMENT_WORKFLOW.md corrected (load order: open-iov-vfio BEFORE nvidia; stock-driver blacklist note) --- kernel/gsp_rpc_client.c | 40 ++++++++++++++++++++++++++++++++++------ 1 file changed, 34 insertions(+), 6 deletions(-) (limited to 'kernel/gsp_rpc_client.c') diff --git a/kernel/gsp_rpc_client.c b/kernel/gsp_rpc_client.c index ae45513..93c1876 100644 --- a/kernel/gsp_rpc_client.c +++ b/kernel/gsp_rpc_client.c @@ -375,8 +375,8 @@ int gsp_rpc_unpin(struct gsp_client *client, u64 handle, u64 offset, u64 size) /* BAR Trap Emulation */ int gsp_rpc_bar_trap(struct gsp_client *client, - u64 bar_addr, u32 access_type, u32 size, - u64 value, u32 bar_num, u64 *ret_value) + u64 bar_addr, u32 access_type, u32 size, + u64 value, u32 bar_num, u64 *ret_value) { struct gsp_bar_trap_req req = {0}; struct gsp_bar_trap_rsp rsp = {0}; @@ -384,6 +384,17 @@ int gsp_rpc_bar_trap(struct gsp_client *client, u32 seq = gsp_next_seq(client); int ret; + /* In emulation mode there is no real firmware to submit to, and + * submit_raw would ring the very doorbell the emulation thread polls + * (self-triggered RPC livelock + timeout stall). Guest BAR access is + * synchronous MMIO via the shadow mapping and never needs this RPC. + * Real shadow-register handlers are TODO; fail fast and loudly. */ + if (gsp_rpc_emulation_is_enabled()) { + pr_warn_ratelimited("gsp_rpc_bar_trap: not supported in emulation mode (bar=%u addr=0x%llx)\n", + bar_num, bar_addr); + return -ENOTSUPP; + } + req.bar_addr = bar_addr; req.access_type = access_type; req.size = size; @@ -413,9 +424,19 @@ int gsp_rpc_migrate_save(struct gsp_client *client, struct gsp_migrate_req req = {0}; struct gsp_migrate_rsp rsp = {0}; struct gsp_rpc_response response = {0}; - u32 seq = gsp_next_seq(client); + u32 seq; int ret; + /* Emulation mode: no real firmware; submit_raw would ring the doorbell + * the emulation thread polls (self-triggered livelock + 30s stall). + * Live migration over the emulated vGPU is not yet implemented; + * see kernel/migration.c for the 4-phase host-side protocol work. */ + if (gsp_rpc_emulation_is_enabled()) { + pr_warn_ratelimited("gsp_rpc_migrate_save: not supported in emulation mode\n"); + return -ENOTSUPP; + } + + seq = gsp_next_seq(client); req.src_gpu_id = src_gpu_id; req.dst_gpu_id = dst_gpu_id; req.memory_bitmap = memory_bitmap; @@ -444,9 +465,16 @@ int gsp_rpc_migrate_restore(struct gsp_client *client, { struct gsp_migrate_req req = {0}; struct gsp_rpc_response response = {0}; - u32 seq = gsp_next_seq(client); + u32 seq; int ret; + /* Emulation mode: no real firmware; see gsp_rpc_migrate_save note. */ + if (gsp_rpc_emulation_is_enabled()) { + pr_warn_ratelimited("gsp_rpc_migrate_restore: not supported in emulation mode\n"); + return -ENOTSUPP; + } + + seq = gsp_next_seq(client); req.src_gpu_id = src_gpu_id; req.dst_gpu_id = dst_gpu_id; req.memory_bitmap = memory_bitmap; @@ -777,7 +805,7 @@ int gsp_rpc_schedule(struct gsp_client *client, u32 seq = gsp_next_seq(client); int ret; - if (gsp_emulation_enabled) { + if (gsp_rpc_emulation_is_enabled()) { struct gsp_sched_work *sched = kzalloc(sizeof(*sched), GFP_KERNEL); if (!sched) return -ENOMEM; @@ -827,7 +855,7 @@ int gsp_rpc_yield(struct gsp_client *client) u32 seq = gsp_next_seq(client); int ret; - if (gsp_emulation_enabled) { + if (gsp_rpc_emulation_is_enabled()) { /* In emulation, yield is a no-op success */ return 0; } -- cgit v1.2.3