Add no-create-imex-channels command line option

This change adds a no-create-imex-channels command line option to opt-out
of the creation of imex channel device nodes.

Note that the creation of device nodes is only triggered if --load-kmods
is specified.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

Author: elezar

src/cli/main.c

@@ -32,6 +32,7 @@ static struct argp usage = {
                 {"user", 'u', "UID[:GID]", OPTION_ARG_OPTIONAL, "User and group to use for privilege separation", -1},
                 {"root", 'r', "PATH", 0, "Path to the driver root directory", -1},
                 {"ldcache", 'l', "FILE", 0, "Path to the system's DSO cache", -1},
+                {"no-create-imex-channels", 0x80, NULL, 0, "Don't automatically create IMEX channel device nodes", -1},
                 {NULL, 0, NULL, 0, "Commands:", 0},
                 {"info", 0, NULL, OPTION_DOC|OPTION_NO_USAGE, "Report information about the driver and devices", 0},
                 {"list", 0, NULL, OPTION_DOC|OPTION_NO_USAGE, "List driver components", 0},
@@ -112,6 +113,10 @@ parser(int key, char *arg, struct argp_state *state)
         case 'l':
                 ctx->ldcache = arg;
                 break;
+        case 0x80:
+                if (str_join(&err, &ctx->init_flags, "no-create-imex-channels", " ") < 0)
+                        goto fatal;
+                break;
         case ARGP_KEY_ARGS:
                 state->argv += state->next;
                 state->argc -= state->next;

src/nvc.c

@@ -33,7 +33,7 @@
 #include "xfuncs.h"
 
 static int init_within_userns(struct error *);
-static int load_kernel_modules(struct error *, const char *, const struct nvc_imex_info *);
+static int load_kernel_modules(struct error *, const char *, const struct nvc_imex_info *, int32_t);
 static int copy_config(struct error *, struct nvc_context *, const struct nvc_config *);
 
 const char interpreter[] __attribute__((section(".interp"))) = LIB_DIR "/" LD_SO;
@@ -229,7 +229,7 @@ mig_nvcaps_mknodes(struct error *err, int num_gpus) {
 }
 
 static int
-load_kernel_modules(struct error *err, const char *root, const struct nvc_imex_info *imex)
+load_kernel_modules(struct error *err, const char *root, const struct nvc_imex_info *imex, int32_t flags)
 {
         int userns;
         pid_t pid;
@@ -290,10 +290,13 @@ load_kernel_modules(struct error *err, const char *root, const struct nvc_imex_i
                         log_info("running mknod for all nvcaps in " NV_CAPS_DEVICE_DIR);
                         if (mig_nvcaps_mknodes(err, devs.num_matches) < 0)
                                 log_errf("could not create kernel module device nodes: %s", err->msg);
-                        for (int i = 0; i < (int)imex->nchans; ++i) {
-                                log_infof("running mknod for " NV_CAPS_IMEX_DEVICE_PATH, imex->chans[i].id);
-                                if (nvidia_cap_imex_channel_mknod(imex->chans[i].id) == 0)
-                                    log_errf("could not mknod for IMEX channel %d", imex->chans[i].id);
+
+                        if (!(flags & OPT_NO_CREATE_IMEX_CHANNELS)) {
+                                for (int i = 0; i < (int)imex->nchans; ++i) {
+                                        log_infof("running mknod for " NV_CAPS_IMEX_DEVICE_PATH, imex->chans[i].id);
+                                        if (nvidia_cap_imex_channel_mknod(imex->chans[i].id) == 0)
+                                                log_errf("could not mknod for IMEX channel %d", imex->chans[i].id);
+                                }
                         }
                         error_reset(err);
                 }
@@ -420,7 +423,7 @@ nvc_init(struct nvc_context *ctx, const struct nvc_config *cfg, const char *opts
         if (flags & OPT_LOAD_KMODS) {
                 if (ctx->dxcore.initialized)
                         log_warn("skipping kernel modules load on WSL");
-                else if (load_kernel_modules(&ctx->err, ctx->cfg.root, &ctx->cfg.imex) < 0)
+                else if (load_kernel_modules(&ctx->err, ctx->cfg.root, &ctx->cfg.imex, flags) < 0)
                         goto fail;
         }
 

src/options.h

@@ -16,11 +16,13 @@ struct option {
 
 /* Library options */
 enum {
-        OPT_LOAD_KMODS = 1 << 0,
+        OPT_LOAD_KMODS              = 1 << 0,
+        OPT_NO_CREATE_IMEX_CHANNELS = 1 << 1,
 };
 
 static const struct option library_opts[] = {
         {"load-kmods", OPT_LOAD_KMODS},
+        {"no-create-imex-channels", OPT_NO_CREATE_IMEX_CHANNELS}
 };
 
 static const char * const default_library_opts = "";