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Foundry/barswap/tests/roundrobin_persist.c

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/* SPDX-License-Identifier: AGPL-3.0-or-later */
/* Copyright (C) 2026 David (Corey) Herrera */
#define _GNU_SOURCE
/*
* roundrobin_persist.c — No-teardown round-robin multi-die persistence test
*
* Proves the production switch mechanism for the K80 barswap rig: nvidia is
* loaded EXACTLY ONCE and never rmmod'd. Weights stay resident in each die's
* VRAM, and we move between dies purely by:
*
* 1. cuCtxDestroy — drop the current die's CUDA context (driver stays)
* 2. PCI unbind — write the old device's BDF to .../nvidia/unbind
* 3. bs_acquire(die) — barswap maps the next die into the single MMIO slot
* 4. driver_override — clear it on the target, "none" on every other GK210
* 5. PCI bind — write the new device's BDF to .../nvidia/bind
* (or, on the very first switch only, modprobe once)
* 6. cuCtxCreate — fresh context on device 0 (== the slot die)
*
* This is the no-teardown analogue of xcard_persist.c. xcard_persist proves
* persistence across a full driver unload/reload between dies; this proves the
* SAME persistence while the nvidia module never leaves the kernel — only the
* single active PCI function is rebound. That is the mechanism we actually ship.
*
* Per-die payload is a distinct pattern seeded from a real SmolLM2 weight chunk
* (per-die file offset) so a stale read of the wrong die's VRAM cannot pass.
*
* Persistence is verified the vram_persist.c way (lines 270-315): after
* re-establishing a context on the die, allocate same-size buffers in the SAME
* order as Phase 1 so they land on the same physical VRAM, read back WITHOUT
* writing, and compare to the recorded expected pattern + compute result.
*
* Reuses (verbatim where noted):
* - test_swap.c : discover_gk210s, read_bar0, find_acquired_bdf,
* set_driver_override, block_all_except, unblock_all
* - compute_persist.c : the dlopen CUDA scaffolding + the slow_add PTX kernel
* - vram_persist.c : the same-size-realloc persistence-verify trick
*
* Usage (on a K80 host, as root):
* make roundrobin-persist
* sudo ./barswap/tests/roundrobin_persist <die0> <die1> ...
* e.g. sudo ./barswap/tests/roundrobin_persist 0 2 4 6 8 10 12 14
*
* SmolLM2 payload path: argv has priority via none (it's all dies); the path
* comes from $SMOL_GGUF, else the SMOL_GGUF_DEFAULT #define. Missing file ->
* synthetic per-die ramp (noted in output).
*
* On a host with no barswap device (e.g. the Mac) it prints [SKIP] and exits 0,
* so it compiles, links, and runs everywhere. Shells out to modprobe ONCE and
* to sysfs bind/unbind — must run as root. Calls _Exit() at the end because the
* rig's CUDA atexit teardown hangs after manual swaps.
*
* @status Builds clean on Mac (SKIP path). Not yet run on hardware.
* @issues None
* @todo None
*/
#include <dirent.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "barswap/barswap.h"
#define COLOR_GREEN "\033[92m"
#define COLOR_RED "\033[31m"
#define COLOR_YELLOW "\033[93m"
#define COLOR_RESET "\033[0m"
#define MAX_DIES BS_MAX_DIES
/* Default SmolLM2 weights path; override with $SMOL_GGUF. */
#define SMOL_GGUF_DEFAULT "/root/n2-test/models/SmolLM2-135M-Instruct-Q8_0.gguf"
/* ================================================================
* GK210 enumeration + driver_override protocol (from test_swap.c)
* ================================================================ */
/* BDF strings for all GK210 devices found in sysfs */
static char gk210_bdf[MAX_DIES][16];
static int n_gk210;
/*
* Discover GK210 device BDFs from sysfs (vendor 0x10de, device 0x102d).
* Verbatim port of test_swap.c:discover_gk210s().
*/
static int discover_gk210s(void)
{
FILE *fp;
char path[512], buf[16];
DIR *dir;
struct dirent *ent;
char *bdfs[MAX_DIES];
int count = 0;
dir = opendir("/sys/bus/pci/devices");
if (!dir)
return 0;
while ((ent = readdir(dir)) != NULL) {
if (ent->d_name[0] == '.')
continue;
snprintf(path, sizeof(path), "/sys/bus/pci/devices/%s/vendor", ent->d_name);
fp = fopen(path, "r");
if (!fp)
continue;
if (!fgets(buf, sizeof(buf), fp)) { fclose(fp); continue; }
fclose(fp);
if (strncmp(buf, "0x10de", 6) != 0)
continue;
snprintf(path, sizeof(path), "/sys/bus/pci/devices/%s/device", ent->d_name);
fp = fopen(path, "r");
if (!fp)
continue;
if (!fgets(buf, sizeof(buf), fp)) { fclose(fp); continue; }
fclose(fp);
if (strncmp(buf, "0x102d", 6) != 0)
continue;
if (count < MAX_DIES) {
bdfs[count] = strdup(ent->d_name);
count++;
}
}
closedir(dir);
/* Sort by BDF name */
for (int i = 0; i < count - 1; i++)
for (int j = i + 1; j < count; j++)
if (strcmp(bdfs[i], bdfs[j]) > 0) {
char *tmp = bdfs[i]; bdfs[i] = bdfs[j]; bdfs[j] = tmp;
}
for (int i = 0; i < count; i++) {
snprintf(gk210_bdf[i], sizeof(gk210_bdf[i]), "%s", bdfs[i]);
free(bdfs[i]);
}
n_gk210 = count;
return count;
}
/*
* Read BAR 0 value from sysfs for a PCI device.
* Returns the resource start address, or 0 if unreadable/unmapped.
* Verbatim port of test_swap.c:read_bar0().
*/
static uint64_t read_bar0(const char *bdf)
{
char path[512], buf[256];
uint64_t start = 0;
snprintf(path, sizeof(path), "/sys/bus/pci/devices/%s/resource", bdf);
FILE *fp = fopen(path, "r");
if (!fp)
return 0;
/* First line of 'resource' file is BAR 0: start end flags */
if (fgets(buf, sizeof(buf), fp))
start = strtoull(buf, NULL, 16);
fclose(fp);
return start;
}
/*
* Find which GK210 BDF currently has BARs programmed into the MMIO slot.
* Only the acquired die has a non-zero BAR 0 (the rest are zeroed on release).
* Mirrors test_swap.c:find_acquired_bdf(), keyed on "non-zero" since the
* barswap lib's bs_gpu does not expose bar0_addr.
* Returns the index into gk210_bdf[], or -1 if none found.
*/
static int find_acquired_bdf(void)
{
for (int i = 0; i < n_gk210; i++) {
if (read_bar0(gk210_bdf[i]) != 0)
return i;
}
return -1;
}
/*
* Write a NUL-terminated string to a sysfs attribute (O_WRONLY, write, close).
* Returns 0 on success, -1 on error (open or write failure), reporting via
* stderr. The trailing newline expected by the PCI bind/unbind attributes must
* be included by the caller.
*/
static int sysfs_write(const char *path, const char *str)
{
int fd = open(path, O_WRONLY);
if (fd < 0) {
fprintf(stderr, " sysfs_write: open(%s) failed\n", path);
return -1;
}
ssize_t want = (ssize_t)strlen(str);
ssize_t got = write(fd, str, (size_t)want);
close(fd);
if (got != want) {
fprintf(stderr, " sysfs_write: write(%s, \"%s\") failed (%zd/%zd)\n",
path, str, got, want);
return -1;
}
return 0;
}
static void set_driver_override(const char *bdf, const char *value)
{
char path[512];
int fd;
snprintf(path, sizeof(path), "/sys/bus/pci/devices/%s/driver_override", bdf);
fd = open(path, O_WRONLY);
if (fd < 0)
return;
if (*value == '\0') {
/* Write newline to clear override — 0-byte write is ignored by VFS */
if (write(fd, "\n", 1) < 0) { /* best-effort */ }
} else {
if (write(fd, value, strlen(value)) < 0) { /* best-effort */ }
}
close(fd);
}
/*
* Block all GK210 devices except the one at bdf_index, so nvidia only binds
* the acquired die. Verbatim port of test_swap.c:block_all_except().
*/
static void block_all_except(int bdf_index)
{
for (int i = 0; i < n_gk210; i++) {
if (i == bdf_index)
set_driver_override(gk210_bdf[i], ""); /* clear — allow nvidia */
else
set_driver_override(gk210_bdf[i], "none"); /* block */
}
}
static void unblock_all(void)
{
for (int i = 0; i < n_gk210; i++)
set_driver_override(gk210_bdf[i], "");
}
/*
* Load nvidia ONCE for the whole run. Mirrors compute_persist.c:load_nvidia().
* After this returns the module stays resident — it is never unloaded.
*/
static int load_nvidia_once(void)
{
int ret;
/* Each module loaded separately with --ignore-install: "install nvidia
* /bin/false" in modprobe.d otherwise blocks dependency resolution. */
ret = system("modprobe --ignore-install nvidia 2>/dev/null");
if (ret != 0)
return -1;
sleep(1);
/* nvidia_uvm is required for cuInit to succeed */
ret = system("modprobe --ignore-install nvidia_uvm 2>/dev/null");
if (ret != 0)
return -1;
sleep(1);
return 0;
}
/*
* Confirm the nvidia module is still resident in the kernel. Reads
* /proc/modules and looks for the "nvidia " entry. Returns 1 if present.
* Used at the end to assert the module never left.
*/
static int nvidia_module_present(void)
{
FILE *fp = fopen("/proc/modules", "r");
if (!fp)
return 0;
char line[256];
int found = 0;
while (fgets(line, sizeof(line), fp)) {
if (strncmp(line, "nvidia ", 7) == 0) { found = 1; break; }
}
fclose(fp);
return found;
}
/* ================================================================
* CUDA driver API via dlopen (from compute_persist.c + vram_persist.c)
* ================================================================ */
typedef int CUresult;
typedef int CUdevice;
typedef void *CUcontext;
typedef void *CUmodule;
typedef void *CUfunction;
typedef void *CUstream;
typedef unsigned long long CUdeviceptr;
#define CUDA_SUCCESS 0
typedef CUresult (*pfn_cuInit)(unsigned int);
typedef CUresult (*pfn_cuDeviceGet)(CUdevice *, int);
typedef CUresult (*pfn_cuCtxCreate)(CUcontext *, unsigned int, CUdevice);
typedef CUresult (*pfn_cuCtxDestroy)(CUcontext);
typedef CUresult (*pfn_cuCtxSynchronize)(void);
typedef CUresult (*pfn_cuMemAlloc)(CUdeviceptr *, size_t);
typedef CUresult (*pfn_cuMemFree)(CUdeviceptr);
typedef CUresult (*pfn_cuMemcpyHtoD)(CUdeviceptr, const void *, size_t);
typedef CUresult (*pfn_cuMemcpyDtoH)(void *, CUdeviceptr, size_t);
typedef CUresult (*pfn_cuModuleLoadData)(CUmodule *, const void *);
typedef CUresult (*pfn_cuModuleGetFunction)(CUfunction *, CUmodule, const char *);
typedef CUresult (*pfn_cuLaunchKernel)(CUfunction,
unsigned int, unsigned int, unsigned int,
unsigned int, unsigned int, unsigned int,
unsigned int, CUstream, void **, void **);
static void *libcuda = NULL;
static pfn_cuInit p_cuInit;
static pfn_cuDeviceGet p_cuDeviceGet;
static pfn_cuCtxCreate p_cuCtxCreate;
static pfn_cuCtxDestroy p_cuCtxDestroy;
static pfn_cuCtxSynchronize p_cuCtxSynchronize;
static pfn_cuMemAlloc p_cuMemAlloc;
static pfn_cuMemFree p_cuMemFree;
static pfn_cuMemcpyHtoD p_cuMemcpyHtoD;
static pfn_cuMemcpyDtoH p_cuMemcpyDtoH;
static pfn_cuModuleLoadData p_cuModuleLoadData;
static pfn_cuModuleGetFunction p_cuModuleGetFunction;
static pfn_cuLaunchKernel p_cuLaunchKernel;
/*
* Embedded PTX kernel — adds 1.0 to each element `iters` times.
* Verbatim port of compute_persist.c:slow_add_ptx (entry "slow_add").
* out[i] = in[i] + iters, exact in float32 while values stay under 2^24.
*/
static const char *slow_add_ptx =
".version 5.0\n"
".target sm_37\n"
".address_size 64\n"
"\n"
".visible .entry slow_add(\n"
" .param .u64 p_out,\n"
" .param .u64 p_in,\n"
" .param .u32 p_n,\n"
" .param .u32 p_iters\n"
") {\n"
" .reg .u32 %r<10>;\n"
" .reg .u64 %rd<10>;\n"
" .reg .f32 %f<4>;\n"
" .reg .pred %p1;\n"
"\n"
" mov.u32 %r0, %tid.x;\n"
" mov.u32 %r1, %ctaid.x;\n"
" mov.u32 %r2, %ntid.x;\n"
" mad.lo.u32 %r0, %r1, %r2, %r0;\n"
"\n"
" ld.param.u32 %r3, [p_n];\n"
" setp.ge.u32 %p1, %r0, %r3;\n"
" @%p1 bra $L_done;\n"
"\n"
" ld.param.u64 %rd0, [p_in];\n"
" cvt.u64.u32 %rd1, %r0;\n"
" shl.b64 %rd1, %rd1, 2;\n"
" add.u64 %rd0, %rd0, %rd1;\n"
" ld.global.f32 %f0, [%rd0];\n"
"\n"
" ld.param.u32 %r4, [p_iters];\n"
" mov.u32 %r5, 0;\n"
" mov.f32 %f1, 0f3F800000;\n" /* 1.0f */
"\n"
"$L_loop:\n"
" add.f32 %f0, %f0, %f1;\n"
" add.u32 %r5, %r5, 1;\n"
" setp.lt.u32 %p1, %r5, %r4;\n"
" @%p1 bra $L_loop;\n"
"\n"
" ld.param.u64 %rd2, [p_out];\n"
" cvt.u64.u32 %rd3, %r0;\n"
" shl.b64 %rd3, %rd3, 2;\n"
" add.u64 %rd2, %rd2, %rd3;\n"
" st.global.f32 [%rd2], %f0;\n"
"\n"
"$L_done:\n"
" ret;\n"
"}\n";
static int load_cuda_symbols(void)
{
libcuda = dlopen("libcuda.so.1", RTLD_LAZY);
if (!libcuda)
libcuda = dlopen("libcuda.so", RTLD_LAZY);
if (!libcuda) {
fprintf(stderr, " Cannot dlopen libcuda: %s\n", dlerror());
return -1;
}
/* _v2 symbols where needed (legacy v1 ctx is incompatible). Mirrors
* compute_persist.c:load_cuda_symbols(). */
#define LOAD(name, sym) do { \
p_##name = (pfn_##name)dlsym(libcuda, sym); \
if (!p_##name) { \
fprintf(stderr, " dlsym(%s) failed: %s\n", sym, dlerror()); \
return -1; \
} \
} while (0)
LOAD(cuInit, "cuInit");
LOAD(cuDeviceGet, "cuDeviceGet");
LOAD(cuCtxCreate, "cuCtxCreate_v2");
LOAD(cuCtxDestroy, "cuCtxDestroy_v2");
LOAD(cuCtxSynchronize, "cuCtxSynchronize");
LOAD(cuMemAlloc, "cuMemAlloc_v2");
LOAD(cuMemFree, "cuMemFree_v2");
LOAD(cuMemcpyHtoD, "cuMemcpyHtoD_v2");
LOAD(cuMemcpyDtoH, "cuMemcpyDtoH_v2");
LOAD(cuModuleLoadData, "cuModuleLoadData");
LOAD(cuModuleGetFunction, "cuModuleGetFunction");
LOAD(cuLaunchKernel, "cuLaunchKernel");
#undef LOAD
return 0;
}
/* ================================================================
* SmolLM2 per-die payload
* ================================================================ */
#define N_ELEMENTS (1024 * 1024) /* 1M floats = 4 MB per buffer */
#define N_ITERS 1000 /* 1000 adds per element */
#define BLOCK_SIZE 256
/* Per-die file stride so each die reads a different SmolLM2 region. */
#define SMOL_DIE_STRIDE_BYTES (1024 * 1024) /* 1 MiB apart per die index */
static const char *smol_path; /* resolved once in main() */
static int smol_available; /* 1 if the file opened, 0 -> synthetic fallback */
/*
* Per-die expectation, recorded in Phase 1 and re-checked in Phase 2.
* Each die gets a DISTINCT input pattern so a stale read of the wrong die's
* VRAM cannot masquerade as a pass.
*/
typedef struct die_expectation {
int die_id;
int list_index; /* position in the argv die list (drives offset) */
uint32_t seed; /* distinct per-die seed (from SmolLM2 or synthetic)*/
int bdf_idx; /* gk210_bdf index this die mapped to (-1 if none) */
int phase1_ok; /* Phase 1 wrote + computed successfully */
int vram_pass; /* Phase 2: input pattern survived */
int compute_pass; /* Phase 2: compute result survived */
} die_expectation;
/*
* Derive a distinct 32-bit seed for a die by reading a SmolLM2 weight chunk at
* a per-die file offset and folding its bytes. Falls back to a synthetic seed
* if the file can't be read at that offset. The seed makes the resident pattern
* unmistakably die-specific.
*/
static uint32_t derive_die_seed(int list_index)
{
uint32_t synthetic = 0x9E3779B9u * (uint32_t)(list_index + 1);
if (!smol_available)
return synthetic;
FILE *fp = fopen(smol_path, "rb");
if (!fp)
return synthetic;
off_t offset = (off_t)list_index * SMOL_DIE_STRIDE_BYTES;
unsigned char chunk[4096];
if (fseeko(fp, offset, SEEK_SET) != 0) {
fclose(fp);
return synthetic;
}
size_t got = fread(chunk, 1, sizeof(chunk), fp);
fclose(fp);
if (got == 0)
return synthetic;
/* FNV-1a fold of the chunk -> distinct seed tied to real weight bytes */
uint32_t h = 2166136261u;
for (size_t i = 0; i < got; i++) {
h ^= chunk[i];
h *= 16777619u;
}
return h ? h : synthetic;
}
/*
* Fill a host buffer with a distinct, deterministic per-die pattern derived
* from the die's seed. Values are kept small (0..4095) so that out = in + N_ITERS
* stays exact in float32 (well under 2^24), making the compute check reliable
* regardless of the raw SmolLM2 byte magnitudes.
*/
static void fill_die_pattern(float *host_buf, uint32_t seed)
{
for (int i = 0; i < N_ELEMENTS; i++) {
uint32_t v = (seed + (uint32_t)i * 2654435761u) & 0xFFFu; /* 0..4095 */
host_buf[i] = (float)v;
}
}
/* Host-side expected compute result for element i: in[i] + N_ITERS. */
static float expected_compute_at(uint32_t seed, int i)
{
uint32_t v = (seed + (uint32_t)i * 2654435761u) & 0xFFFu;
return (float)v + (float)N_ITERS;
}
/* ================================================================
* The switch primitive — THE point of this test
* ================================================================ */
static bs_context *g_bs;
static int active_bdf_idx = -1; /* gk210_bdf index currently nvidia-bound */
static int nvidia_loaded; /* set after the single modprobe */
static bs_gpu *current_gpu; /* die currently in the MMIO slot */
static CUcontext current_ctx; /* live ctx on the slot die (resident) */
/*
* Unbind a single PCI device from the nvidia driver via sysfs.
* Writes "<bdf>\n" to /sys/bus/pci/drivers/nvidia/unbind.
*/
static int pci_unbind(const char *bdf)
{
char val[32];
snprintf(val, sizeof(val), "%s\n", bdf);
return sysfs_write("/sys/bus/pci/drivers/nvidia/unbind", val);
}
/*
* Bind a single PCI device to the nvidia driver via sysfs (re-probe just it).
* Writes "<bdf>\n" to /sys/bus/pci/drivers/nvidia/bind.
*/
static int pci_bind(const char *bdf)
{
char val[32];
snprintf(val, sizeof(val), "%s\n", bdf);
return sysfs_write("/sys/bus/pci/drivers/nvidia/bind", val);
}
/*
* switch_to — move the active GPU to `die`, NO driver teardown.
*
* Drops the current context and PCI-unbinds the old device, acquires the new
* die into the MMIO slot, points driver_override at it, and either loads nvidia
* (first switch ONLY) or PCI-binds just this device. Leaves a fresh CUDA context
* live in current_ctx and the handle in current_gpu. Returns 0 on success.
*
* The nvidia module is loaded exactly once across the whole run; every later
* switch is cuCtxDestroy -> unbind -> acquire -> bind. nvidia is NEVER rmmod'd.
*/
static int switch_to(int die)
{
CUresult err;
CUdevice dev;
/* 1. Drop the previous die's context + unbind its PCI function (driver
* stays resident). */
if (active_bdf_idx >= 0) {
if (current_ctx) {
p_cuCtxDestroy(current_ctx);
current_ctx = NULL;
}
printf(" switch: unbinding old device %s\n", gk210_bdf[active_bdf_idx]);
if (pci_unbind(gk210_bdf[active_bdf_idx]) != 0)
fprintf(stderr, " warning: unbind of %s failed\n",
gk210_bdf[active_bdf_idx]);
}
/* Release the old slot mapping so the next acquire is clean. */
if (current_gpu) {
bs_release(g_bs, current_gpu);
current_gpu = NULL;
}
/* 2. Map the target die into the single MMIO slot. */
current_gpu = bs_acquire(g_bs, die);
if (!current_gpu) {
fprintf(stderr, " switch: bs_acquire(%d) failed\n", die);
return -1;
}
/* 3. Identify which GK210 now occupies the slot. */
int idx = find_acquired_bdf();
if (idx < 0) {
fprintf(stderr, " switch: could not find acquired BDF for die %d\n", die);
return -1;
}
active_bdf_idx = idx;
printf(" switch: target die %d -> acquired GK210 %s, active BDF %s\n",
die, gk210_bdf[idx], gk210_bdf[idx]);
/* 4. Allow nvidia to bind only the acquired die. */
block_all_except(idx);
/* 5. Load nvidia ONCE, ever; afterwards just re-probe this one device. */
if (!nvidia_loaded) {
printf(" switch: loading nvidia (first switch only)\n");
if (load_nvidia_once() != 0) {
fprintf(stderr, " switch: nvidia load failed\n");
return -1;
}
nvidia_loaded = 1;
/* First modprobe probes the only allowed device, binding it for us. */
} else {
printf(" switch: binding device %s\n", gk210_bdf[idx]);
if (pci_bind(gk210_bdf[idx]) != 0)
fprintf(stderr, " warning: bind of %s failed\n", gk210_bdf[idx]);
}
/* 6. Fresh context on device 0 (== the slot die). */
if ((err = p_cuInit(0)) != CUDA_SUCCESS) {
fprintf(stderr, " switch: cuInit failed: %d\n", err);
return -1;
}
if ((err = p_cuDeviceGet(&dev, 0)) != CUDA_SUCCESS) {
fprintf(stderr, " switch: cuDeviceGet failed: %d\n", err);
return -1;
}
if ((err = p_cuCtxCreate(&current_ctx, 0, dev)) != CUDA_SUCCESS) {
fprintf(stderr, " switch: cuCtxCreate failed: %d\n", err);
current_ctx = NULL;
return -1;
}
return 0;
}
/* ================================================================
* Phases
* ================================================================ */
/*
* Phase 1 for one die: switch_to (NO teardown), allocate d_in/d_out, upload the
* die's distinct pattern, launch the kernel (out = in + N_ITERS), sync, and
* self-verify. Buffers and the context are LEFT resident — the next switch_to
* handles cuCtxDestroy + PCI unbind. Returns 0 on success.
*/
static int phase1_load_resident(die_expectation *exp)
{
CUresult err;
CUdeviceptr d_in = 0, d_out = 0;
CUmodule mod;
CUfunction kern;
float *h_in = NULL, *h_check = NULL;
int rc = -1;
printf(COLOR_YELLOW "\n[Phase 1] die %d — load resident (no teardown)" COLOR_RESET "\n",
exp->die_id);
if (switch_to(exp->die_id) != 0)
return -1;
exp->bdf_idx = active_bdf_idx;
size_t buf_bytes = (size_t)N_ELEMENTS * sizeof(float);
if ((err = p_cuMemAlloc(&d_in, buf_bytes)) != CUDA_SUCCESS) {
fprintf(stderr, " cuMemAlloc(in) failed: %d\n", err); goto done;
}
if ((err = p_cuMemAlloc(&d_out, buf_bytes)) != CUDA_SUCCESS) {
fprintf(stderr, " cuMemAlloc(out) failed: %d\n", err); goto done;
}
h_in = (float *)malloc(buf_bytes);
fill_die_pattern(h_in, exp->seed);
if ((err = p_cuMemcpyHtoD(d_in, h_in, buf_bytes)) != CUDA_SUCCESS) {
fprintf(stderr, " cuMemcpyHtoD failed: %d\n", err); goto done;
}
if ((err = p_cuModuleLoadData(&mod, slow_add_ptx)) != CUDA_SUCCESS) {
fprintf(stderr, " cuModuleLoadData failed: %d\n", err); goto done;
}
if ((err = p_cuModuleGetFunction(&kern, mod, "slow_add")) != CUDA_SUCCESS) {
fprintf(stderr, " cuModuleGetFunction failed: %d\n", err); goto done;
}
unsigned int n = N_ELEMENTS, iters = N_ITERS;
unsigned int grid = (N_ELEMENTS + BLOCK_SIZE - 1) / BLOCK_SIZE;
void *args[] = { &d_out, &d_in, &n, &iters };
if ((err = p_cuLaunchKernel(kern, grid, 1, 1, BLOCK_SIZE, 1, 1,
0, NULL, args, NULL)) != CUDA_SUCCESS) {
fprintf(stderr, " cuLaunchKernel failed: %d\n", err); goto done;
}
if ((err = p_cuCtxSynchronize()) != CUDA_SUCCESS) {
fprintf(stderr, " cuCtxSynchronize failed: %d\n", err); goto done;
}
/* In-die self-check before we ever leave this die. */
h_check = (float *)malloc(buf_bytes);
p_cuMemcpyDtoH(h_check, d_out, buf_bytes);
int ok = 1;
for (int i = 0; i < N_ELEMENTS; i++)
if (h_check[i] != expected_compute_at(exp->seed, i)) { ok = 0; break; }
if (!ok) {
fprintf(stderr, " Phase 1 self-check failed for die %d\n", exp->die_id);
goto done;
}
printf(" die %d: seed=0x%08x, pattern uploaded + compute (out=in+%d), verify OK\n",
exp->die_id, exp->seed, N_ITERS);
printf(" die %d: buffers LEFT resident, ctx LEFT live (next switch tears down)\n",
exp->die_id);
exp->phase1_ok = 1;
rc = 0;
done:
/* Free host buffers only. GPU buffers stay allocated; the context stays
* live — both are intentionally left resident across the switch. */
free(h_in);
free(h_check);
return rc;
}
/*
* Phase 2 for one die: switch_to, re-allocate the SAME two buffers in the SAME
* order (in then out) so they land on the same physical VRAM, read back WITHOUT
* writing, and compare to the recorded pattern + compute result.
* Verification mirrors vram_persist.c lines 278 / 290-292 / 304-315.
* Returns 0 if the check ran, -1 if it could not run.
*/
static int phase2_verify(die_expectation *exp)
{
CUresult err;
CUdeviceptr d_in = 0, d_out = 0;
float *r_in = NULL, *r_out = NULL;
int rc = -1;
printf(COLOR_YELLOW "\n[Phase 2] die %d — verify resident (no teardown)" COLOR_RESET "\n",
exp->die_id);
if (switch_to(exp->die_id) != 0)
return -1;
size_t buf_bytes = (size_t)N_ELEMENTS * sizeof(float);
/* Same-size, same-order allocations as Phase 1 -> same physical VRAM.
* (vram_persist.c:278) */
if ((err = p_cuMemAlloc(&d_in, buf_bytes)) != CUDA_SUCCESS) {
fprintf(stderr, " cuMemAlloc(in) failed: %d\n", err); goto done;
}
if ((err = p_cuMemAlloc(&d_out, buf_bytes)) != CUDA_SUCCESS) {
fprintf(stderr, " cuMemAlloc(out) failed: %d\n", err); goto done;
}
/* Read back without writing — checking for residual data.
* (vram_persist.c:290-292) */
r_in = (float *)malloc(buf_bytes);
r_out = (float *)malloc(buf_bytes);
memset(r_in, 0, buf_bytes);
memset(r_out, 0, buf_bytes);
p_cuMemcpyDtoH(r_in, d_in, buf_bytes);
p_cuMemcpyDtoH(r_out, d_out, buf_bytes);
/* Tally per-element matches (vram_persist.c:304-315). */
int in_match = 0, out_match = 0;
for (int i = 0; i < N_ELEMENTS; i++) {
uint32_t v = (exp->seed + (uint32_t)i * 2654435761u) & 0xFFFu;
if (r_in[i] == (float)v)
in_match++;
if (r_out[i] == (float)v + (float)N_ITERS)
out_match++;
}
exp->vram_pass = (in_match == N_ELEMENTS);
exp->compute_pass = (out_match == N_ELEMENTS);
printf(" die %d: vram pattern %d/%d, compute result %d/%d\n",
exp->die_id, in_match, N_ELEMENTS, out_match, N_ELEMENTS);
rc = 0;
done:
if (d_in) p_cuMemFree(d_in);
if (d_out) p_cuMemFree(d_out);
free(r_in);
free(r_out);
return rc;
}
int main(int argc, char *argv[])
{
setvbuf(stdout, NULL, _IONBF, 0);
setvbuf(stderr, NULL, _IONBF, 0);
printf("=== Round-Robin No-Teardown Persistence Test ===\n\n");
/* Gate on barswap availability so this compiles+runs everywhere. */
g_bs = bs_init();
if (!g_bs) {
printf("[SKIP] no barswap (bs_init failed — not on a K80 host)\n");
return 0;
}
if (argc < 2) {
fprintf(stderr,
"usage: %s <die0> <die1> ... (e.g. %s 0 2 4 6 8 10 12 14)\n",
argv[0], argv[0]);
bs_free(g_bs);
return 1;
}
if (getuid() != 0) {
fprintf(stderr, "error: must run as root (sudo) — needs modprobe + sysfs\n");
bs_free(g_bs);
return 1;
}
/* Resolve SmolLM2 payload source: $SMOL_GGUF, else the default path. */
smol_path = getenv("SMOL_GGUF");
if (!smol_path || !*smol_path)
smol_path = SMOL_GGUF_DEFAULT;
FILE *probe = fopen(smol_path, "rb");
smol_available = (probe != NULL);
if (probe)
fclose(probe);
int n_dies = argc - 1;
if (n_dies > MAX_DIES)
n_dies = MAX_DIES;
die_expectation dies[MAX_DIES] = {0};
for (int i = 0; i < n_dies; i++) {
dies[i].die_id = atoi(argv[i + 1]);
dies[i].list_index = i;
dies[i].seed = derive_die_seed(i);
dies[i].bdf_idx = -1;
}
discover_gk210s();
/* Load CUDA symbols once; the nvidia module itself is loaded lazily by the
* first switch_to and then never unloaded. */
if (load_cuda_symbols() != 0) {
bs_free(g_bs);
return 1;
}
printf("barswap: %u dies available, %d GK210s in sysfs\n",
bs_num_dies(g_bs), n_gk210);
printf("SmolLM2 payload: %s (%s)\n", smol_path,
smol_available ? "found — per-die file offsets" : "MISSING — synthetic ramp");
printf("testing %d dies (no driver teardown between dies):", n_dies);
for (int i = 0; i < n_dies; i++)
printf(" %d", dies[i].die_id);
printf("\n");
/* Phase 1: load each die's resident pattern, leaving ctx + buffers live.
* Between dies there is NO rmmod — only cuCtxDestroy + PCI unbind/bind. */
int phase1_failures = 0;
for (int i = 0; i < n_dies; i++)
if (phase1_load_resident(&dies[i]) != 0)
phase1_failures++;
/* Phase 2: re-verify each die retained VRAM + compute result. */
int phase2_failures = 0;
for (int i = 0; i < n_dies; i++)
if (phase2_verify(&dies[i]) != 0)
phase2_failures++;
/* Final cleanup of the last resident context + slot mapping. nvidia stays. */
if (current_ctx) {
p_cuCtxDestroy(current_ctx);
current_ctx = NULL;
}
if (current_gpu) {
bs_release(g_bs, current_gpu);
current_gpu = NULL;
}
unblock_all();
/* Report */
printf("\n=== Results ===\n");
int all_pass = 1;
for (int i = 0; i < n_dies; i++) {
die_expectation *d = &dies[i];
int pass = d->phase1_ok && d->vram_pass && d->compute_pass;
if (!pass)
all_pass = 0;
printf("%s die %d (%s):" COLOR_RESET " vram=%s compute=%s\n",
pass ? COLOR_GREEN "[PASS]" : COLOR_RED "[FAIL]",
d->die_id,
d->bdf_idx >= 0 ? gk210_bdf[d->bdf_idx] : "bdf n/a",
d->vram_pass ? "ok" : "LOST",
d->compute_pass ? "ok" : "LOST");
}
if (phase1_failures || phase2_failures)
all_pass = 0;
int still_loaded = nvidia_module_present();
if (!still_loaded)
all_pass = 0;
printf("\nnvidia stayed loaded the whole run: %s\n",
still_loaded ? COLOR_GREEN "YES" COLOR_RESET
: COLOR_RED "NO (module left the kernel!)" COLOR_RESET);
printf("\n%s round-robin no-teardown persistence (%d dies)" COLOR_RESET "\n",
all_pass ? COLOR_GREEN "[PASS]" : COLOR_RED "[FAIL]", n_dies);
bs_free(g_bs);
/* The rig's CUDA atexit teardown hangs after manual swaps — hard-exit. */
_Exit(all_pass ? 0 : 1);
}
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