ebpf: improve error trace events

A design pattern of

   trace_foo_error("descriptive string")

is undesirable because it does not allow for filtering trace events
based on the error scenario. Split eBPF error trace event into three
separate events to address this filtering need.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

ebpf/ebpf_rss.c

@@ -53,21 +53,21 @@ static bool ebpf_rss_mmap(struct EBPFRSSContext *ctx)
                                    PROT_READ | PROT_WRITE, MAP_SHARED,
                                    ctx->map_configuration, 0);
     if (ctx->mmap_configuration == MAP_FAILED) {
-        trace_ebpf_error("eBPF RSS", "can not mmap eBPF configuration array");
+        trace_ebpf_rss_mmap_error(ctx, "configuration");
         return false;
     }
     ctx->mmap_toeplitz_key = mmap(NULL, qemu_real_host_page_size(),
                                    PROT_READ | PROT_WRITE, MAP_SHARED,
                                    ctx->map_toeplitz_key, 0);
     if (ctx->mmap_toeplitz_key == MAP_FAILED) {
-        trace_ebpf_error("eBPF RSS", "can not mmap eBPF toeplitz key");
+        trace_ebpf_rss_mmap_error(ctx, "toeplitz key");
         goto toeplitz_fail;
     }
     ctx->mmap_indirections_table = mmap(NULL, qemu_real_host_page_size(),
                                    PROT_READ | PROT_WRITE, MAP_SHARED,
                                    ctx->map_indirections_table, 0);
     if (ctx->mmap_indirections_table == MAP_FAILED) {
-        trace_ebpf_error("eBPF RSS", "can not mmap eBPF indirection table");
+        trace_ebpf_rss_mmap_error(ctx, "indirections table");
         goto indirection_fail;
     }
 
@@ -105,14 +105,14 @@ bool ebpf_rss_load(struct EBPFRSSContext *ctx)
 
     rss_bpf_ctx = rss_bpf__open();
     if (rss_bpf_ctx == NULL) {
-        trace_ebpf_error("eBPF RSS", "can not open eBPF RSS object");
+        trace_ebpf_rss_open_error(ctx);
         goto error;
     }
 
     bpf_program__set_type(rss_bpf_ctx->progs.tun_rss_steering_prog, BPF_PROG_TYPE_SOCKET_FILTER);
 
     if (rss_bpf__load(rss_bpf_ctx)) {
-        trace_ebpf_error("eBPF RSS", "can not load RSS program");
+        trace_ebpf_rss_load_error(ctx);
         goto error;
     }
 

ebpf/trace-events

@@ -1,4 +1,6 @@
 # See docs/devel/tracing.rst for syntax documentation.
 
 # ebpf-rss.c
-ebpf_error(const char *s1, const char *s2) "error in %s: %s"
+ebpf_rss_load_error(void *ctx) "ctx=%p"
+ebpf_rss_mmap_error(void *ctx, const char *object) "ctx=%p object=%s"
+ebpf_rss_open_error(void *ctx) "ctx=%p"