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| -rw-r--r-- | docs/05-operations/01-performance-correctness-security.md | 140 | ||||
| -rw-r--r-- | docs/05-operations/02-debugging-and-maintenance-workflows.md | 157 |
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diff --git a/docs/05-operations/01-performance-correctness-security.md b/docs/05-operations/01-performance-correctness-security.md new file mode 100644 index 0000000..c4d8153 --- /dev/null +++ b/docs/05-operations/01-performance-correctness-security.md @@ -0,0 +1,140 @@ +# Performance, Correctness, and Security Evaluation + +> How we measure whether Open-IOV is any good — and how auditors can verify the +> claims. Numbers without methodology are not accepted here. + +## 1. The evaluation ladder + +Every platform (hardware + driver + hypervisor + guest) is evaluated through +the same five-rung ladder. Each rung is a gate: you do not claim the next one +until the previous one is green and reproducible. + +``` +Rung 1 INITIALIZATION guest driver probes; nvidia-smi; device enumeration +Rung 2 RUNTIME START cuInit; context; allocation; UVM registration +Rung 3 EXECUTION kernels produce correct results; copies verified +Rung 4 SUSTAINED workloads run for hours; faults/errors recoverable +Rung 5 MULTI-TENANT N VMs, isolation + fairness + no cross-talk +``` + +## 2. Correctness + +### 2.1 Test corpus + +| Layer | Tests | +|---|---| +| Device | PCI config validation, BAR sizing, MSI-X semantics, power-management stubs | +| Driver init | guest `nvidia.ko` probe, `nvidia-smi` full query, `deviceQuery` | +| CUDA | `vectorAdd`, reduction, shared-memory kernels, memcpy patterns, streams/events, error injection | +| UVM | oversubscribed memory (fault path), unified memory migration, concurrency | +| Graphics (later) | GLXInfo/VulkanInfo, rendering correctness screenshots | +| Stability | start/stop cycles ×100, VM kill during work, guest reboot in flight | + +### 2.2 Verification methods + +1. **Golden results**: kernel outputs compared against native execution on the + same GPU, byte-for-byte, for deterministic kernels. +2. **Guest self-checks**: the guest's own validation paths are the strongest + signal (UVM asserts, RM validation, CUDA runtime self-tests). Every guest + diagnostic that fires is a test failure for us, even if the workload + continues. +3. **Differential runs**: same workload on (a) native, (b) our device — diff + observables, not just outputs: semaphore value sequences, PUT/GET progress, + interrupt counts. +4. **Negative testing**: inject malformed device behaviour in a lab profile and + require the guest driver to recover exactly as it would on hardware with a + transient error. + +### 2.3 Regression gates + +`make test` runs the host suite. The CI ladder runs the guest suite on a +scheduled cadence and on every release. A rung regression is a release blocker; +the handoff documents carry the current rung. + +## 3. Performance + +### 3.1 Metrics + +| Metric | Definition | Why it matters | +|---|---|---| +| T_init | VM boot → `cuInit` returns | user-visible startup | +| RPC latency p50/p99 | request write → reply visible in status queue | init and management overhead | +| Push overhead | guest submission → engine start (forwarded) | steady-state latency | +| Semaphore completion latency | release written → tracker observes | per-operation sync cost | +| Copy bandwidth | H2D/D2H/D2D, large and small | data-movement quality | +| Kernel throughput | kernels/second for a fixed workload | launch overhead | +| Multi-tenant fairness | per-tenant progress under contention | isolation quality | + +### 3.2 Method + +* **Same-guest baselines**: measure native GPU performance *in the same VM with + a passthrough device* where possible; otherwise on the same hardware with the + same driver. Comparisons across hosts are noise. +* **Warm and cold**: report both; report variance; report the number of runs. +* **Instrument everything**: the emulation timestamps requests and replies + (tracepoints, `trace_printk`, or counters) so overhead is attributable to a + component, not to a mystery. +* **Publish the harness**: the benchmark scripts live in `tools/`, and a + result is not comparable unless produced by them (or an equivalent, + documented harness). + +### 3.3 Targets + +* Initialization: within 2× of native, same guest. +* Synchronization-heavy operations: within an agreed constant factor, published + per operation class. +* Bulk copies and sustained compute: as close to native as the forwarding path + allows; the forwarding design (proxy vs direct) is decided by measurement. + +## 4. Security and isolation + +### 4.1 Threat model + +| Adversary | Capability | Boundary that must hold | +|---|---|---| +| Guest VM (tenant) | full control of its own driver, MMIO, DMA | cannot touch host or other tenants' memory/state | +| Malicious guest driver | arbitrary device programming | emulation must validate everything, fail closed | +| Host user (unprivileged) | can access `/dev/*` permissions given | no privilege escalation via our interfaces | +| Adjacent tenant | shares the GPU | cannot observe timing/state/interrupts beyond policy | +| Supply chain | modified driver/firmware | measured boot (TrenchBoot) verifies the platform | + +### 4.2 Enforcement + +* **Memory isolation is the platform IOMMU's job, and we never weaken it.** + The device performs DMA only through the hypervisor-provided DMA interface + for its own VM. No global mappings, no "identity for convenience". +* **Per-instance state**: every mdev has its own BAR shadows, queues, + interrupt state and emulation context. No shared mutable state between + tenants in the host module. +* **Fail closed**: if a required isolation property cannot be established + (IOMMU absent, DMA mapping failure, inconsistent state), the device refuses + to start and says why in `dmesg`. +* **Interrupts**: per-instance vectors; masked interrupts are queued in the + emulated PBA, not dropped into another tenant's vector. +* **Debug surfaces**: destructive debug parameters are opt-in, documented, and + excluded from hardened builds. Reads are side-effect-free. +* **No secrets in the module**: nothing about one tenant's workload is stored + where another tenant could reach it. + +### 4.3 Auditing + +* The security-relevant code paths are small and enumerated in this document + tree: device registration, DMA access, interrupt injection, memory + translation, and the debug surface. Auditors should be able to enumerate + them mechanically (`grep` for the gate points). +* Each release produces a checklist: threat model reviewed, fail-closed paths + exercised by tests, debug surface verified gated, dependency licenses + unchanged. +* We explicitly invite adversarial review — including of the emulation's + response to malformed guest input. + +## 5. Reporting + +Each release publishes: + +1. **Rung achieved** per platform, with logs. +2. **Performance table** (metrics above) with methodology and variance. +3. **Known issues**, linked to the known-unknowns document. +4. **Security checklist** status. + +This is the only accepted form of a claim in this project. diff --git a/docs/05-operations/02-debugging-and-maintenance-workflows.md b/docs/05-operations/02-debugging-and-maintenance-workflows.md new file mode 100644 index 0000000..bc38a4e --- /dev/null +++ b/docs/05-operations/02-debugging-and-maintenance-workflows.md @@ -0,0 +1,157 @@ +# Debugging and Maintenance Workflows + +> The practical book: how to see what is happening, how to find the cause, and +> how to add a new firmware, driver, hypervisor or hardware version without +> breaking anything. + +## 1. The observability model + +Three layers, in order of usefulness: + +1. **Guest diagnostics** — the guest driver is the best oracle. It prints + precisely what it expected and what it got (e.g. UVM's "Tracker entry for + value N … channel_init()"). Always start here. +2. **Host module trace** — every RPC and every emulation decision is logged + with the `gsp-resman-vfio:` prefix. A full CUDA run produces a few hundred + lines that reconstruct the object tree and the control battery. +3. **Memory observation** — when the problem is in memory state (mappings, + semaphores, pushes), the module's debug parameters read and write guest + physical memory directly. + +## 2. Standard captures for a bug report + +```bash +# Host +sudo dmesg -T | grep -iE 'gsp-resman-vfio|gsp_|nvidia|vfio|mdev' > host.log +./scripts/stack_manager.sh status > status.log +# Guest +sudo dmesg > guest-dmesg.log # include full dmesg +sudo lspci -vvv -d 10de: > guest-lspci.log # config space of the virtual GPU +cat /proc/cmdline > guest-cmdline.log +nvidia-smi -q > nvidia-smi-q.log +``` + +Plus: the emulated driver profile (GPU type, firmware image hash, driver +version) and the exact command sequence used. `tools/guest-diag/push_guest_tools.sh` +collects some of this automatically. + +## 3. Live debugging toolbox + +### 3.1 Kernel logs + +```bash +sudo dmesg -w | grep -iE 'gsp-resman-vfio' # live emulation trace +sudo dmesg -T | grep gsp-resman-vfio | tail -100 # recent +# capture to a file when the ring buffer is small and traffic is heavy: +sudo stdbuf -oL dmesg -w > run.log +``` + +### 3.2 Module debug parameters + +See the host-module doc for the full list. Canonical examples: + +```bash +# Find where a value lives in guest RAM (e.g. a semaphore VA): +echo 0x121000000 | sudo tee /sys/module/open_iov_vfio/parameters/scan_guest_ram + +# Find a decoded method sequence in guest RAM: +echo 0x1,0x21000000,0x1 | sudo tee /sys/module/open_iov_vfio/parameters/scan_seq + +# Write a value to a guest physical address (completing a semaphore release): +echo 0x120299010,0x1 | sudo tee /sys/module/open_iov_vfio/parameters/poke_guest +``` + +**Caution:** all guest-RAM operations run in a kernel thread context by design; +calling them from a normal process context fails with `-EFAULT` (the +hypervisor's DMA interface requires either the mapping's `mm` or no `mm` at +all). This is not a bug. + +### 3.3 QEMU gdbstub (guest virtual memory) + +The reference QEMU configuration exposes a gdbstub (`-gdb tcp::1234`). It can +read guest *virtual* memory through the vCPU's page tables and write to it — +the single most powerful trick we have when the guest's own kernel address +matters: + +```bash +gdb -batch -ex 'target remote :1234' \ + -ex 'x/8wx 0xffff...' -ex 'set *(unsigned int*)0xffff... = 1' +``` + +Workflow that made the memory model tractable: + +1. Find the guest's `page_offset_base` (direct-map base) from + `/proc/kallsyms` in the guest. +2. Convert a kernel CPU VA to a physical address: `PA = VA - page_offset_base`. +3. Use `poke_guest` to write the physical address from the host module, or use + the gdbstub to write the virtual address directly. + +### 3.4 Guest-side tracing + +* `ptrace` tracer (`tools/guest-diag/ptrace_ioctl.c`): libcuda issues raw + syscalls, so `LD_PRELOAD` shims see nothing; PTRACE_SYSCALL with + `PTRACE_GET_SYSCALL_INFO` does. +* UVM debug: `echo 1 > /sys/module/nvidia_uvm/parameters/uvm_debug_prints` + (messages appear as `nvidia-uvm:`). +* kprobes do not work on NVIDIA text (`notrace`); do not waste time on them. + +### 3.5 Failure decision trees + +When a failure is understood, write the decision tree into this document tree +— the tree is what makes the next failure cheap. The field guide's tables are +the result of that discipline so far. + +## 4. Workflows for new inputs + +### 4.1 New firmware version + +1. Add the image under `firmware/<SERIES>-GSP/<VERSION>/` (tracked by LFS). +2. Compute signatures (CRC32/SHA256) with the firmware analyzer. +3. Add a firmware profile entry (addresses/signatures) so runtime analysis can + identify it. +4. Run the driver against a guest using that firmware's matching driver; diff + the RPC/control inventory against the baseline. +5. Add/adjust handlers only where the diff requires it; re-run the ladder. + +### 4.2 New guest driver version + +1. Install the stock driver in a guest (no patches). +2. Capture the full init trace and diff function/control IDs against the + previous version. +3. For each difference: decode against our decompiled study notes for that version + (`g_rpc-structures.h`, `rpc_global_enums.h`, control headers). +4. Add a version-keyed handler or a capability table entry. +5. Re-run rungs 1–2; then the CUDA corpus. + +### 4.3 New hardware generation + +1. Add a hardware profile (PCI IDs, BAR layout, memory geometry, engine list). +2. Run the ladder on that hardware with the closest driver family. +3. Fix differences by configuration first; only add code when an interface + genuinely differs. +4. Publish the profile and the test evidence. + +### 4.4 New hypervisor + +1. Implement the transport boundary (device registration, guest-memory access, + interrupt injection) — the boundary is small by design. +2. Re-run the ladder; the emulation core must not need changes. +3. Document any hypervisor-specific quirk in the debugging docs. + +## 5. Crash and hang recovery + +| Situation | Action | +|---|---| +| Module stuck unloading | `stack_manager.sh cleanup-crash`; reboot if it persists (request approval per project policy) | +| VM wedged, guest filesystem dirty | stop the VM gracefully (`scripts/vgpu_vm.py stop`), fsck via `qemu-nbd` only if needed | +| Guest driver wedged (D-state processes) | reboot the guest; capture dmesg first | +| Kernel oops in the host module | capture the full oops + `dmesg` before reloading | + +## 6. Release engineering + +* Versions are tagged; each tag carries the rung/matrix table and the + performance table for the platforms tested. +* Configuration profiles are versioned with the code; a profile bump is a + reviewed change with evidence. +* The docs in this tree are part of the release: a release that changes + behaviour without updating them is incomplete. |