[PATCH v3 1/6] ebpf: Added eBPF map update through mmap.

[Andrew Melnychenko]

Changed eBPF map updates through mmaped array.
Mmaped arrays provide direct access to map data.
It should omit using bpf_map_update_elem() call,
which may require capabilities that are not present.

Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
---
 ebpf/ebpf_rss.c | 117 ++++++++++++++++++++++++++++++++++++++----------
 ebpf/ebpf_rss.h |   5 +++
 2 files changed, 99 insertions(+), 23 deletions(-)

diff --git a/ebpf/ebpf_rss.c b/ebpf/ebpf_rss.c
index cee658c158b..247f5eee1b6 100644
--- a/ebpf/ebpf_rss.c
+++ b/ebpf/ebpf_rss.c
@@ -27,19 +27,83 @@ void ebpf_rss_init(struct EBPFRSSContext *ctx)
 {
     if (ctx != NULL) {
         ctx->obj = NULL;
+        ctx->program_fd = -1;
+        ctx->map_configuration = -1;
+        ctx->map_toeplitz_key = -1;
+        ctx->map_indirections_table = -1;
+
+        ctx->mmap_configuration = NULL;
+        ctx->mmap_toeplitz_key = NULL;
+        ctx->mmap_indirections_table = NULL;
     }
 }
 
 bool ebpf_rss_is_loaded(struct EBPFRSSContext *ctx)
 {
-    return ctx != NULL && ctx->obj != NULL;
+    return ctx != NULL && (ctx->obj != NULL || ctx->program_fd != -1);
+}
+
+static bool ebpf_rss_mmap(struct EBPFRSSContext *ctx)
+{
+    if (!ebpf_rss_is_loaded(ctx)) {
+        return false;
+    }
+
+    ctx->mmap_configuration = mmap(NULL, qemu_real_host_page_size(),
+                                   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");
+        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");
+        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");
+        goto indirection_fail;
+    }
+
+    return true;
+
+indirection_fail:
+    munmap(ctx->mmap_toeplitz_key, qemu_real_host_page_size());
+toeplitz_fail:
+    munmap(ctx->mmap_configuration, qemu_real_host_page_size());
+
+    ctx->mmap_configuration = NULL;
+    ctx->mmap_toeplitz_key = NULL;
+    ctx->mmap_indirections_table = NULL;
+    return false;
+}
+
+static void ebpf_rss_munmap(struct EBPFRSSContext *ctx)
+{
+    if (!ebpf_rss_is_loaded(ctx)) {
+        return;
+    }
+
+    munmap(ctx->mmap_indirections_table, qemu_real_host_page_size());
+    munmap(ctx->mmap_toeplitz_key, qemu_real_host_page_size());
+    munmap(ctx->mmap_configuration, qemu_real_host_page_size());
+
+    ctx->mmap_configuration = NULL;
+    ctx->mmap_toeplitz_key = NULL;
+    ctx->mmap_indirections_table = NULL;
 }
 
 bool ebpf_rss_load(struct EBPFRSSContext *ctx)
 {
     struct rss_bpf *rss_bpf_ctx;
 
-    if (ctx == NULL) {
+    if (ctx == NULL || ebpf_rss_is_loaded(ctx)) {
         return false;
     }
 
@@ -66,10 +130,18 @@ bool ebpf_rss_load(struct EBPFRSSContext *ctx)
     ctx->map_toeplitz_key = bpf_map__fd(
             rss_bpf_ctx->maps.tap_rss_map_toeplitz_key);
 
+    if (!ebpf_rss_mmap(ctx)) {
+        goto error;
+    }
+
     return true;
 error:
     rss_bpf__destroy(rss_bpf_ctx);
     ctx->obj = NULL;
+    ctx->program_fd = -1;
+    ctx->map_configuration = -1;
+    ctx->map_toeplitz_key = -1;
+    ctx->map_indirections_table = -1;
 
     return false;
 }
@@ -77,15 +149,11 @@ error:
 static bool ebpf_rss_set_config(struct EBPFRSSContext *ctx,
                                 struct EBPFRSSConfig *config)
 {
-    uint32_t map_key = 0;
-
     if (!ebpf_rss_is_loaded(ctx)) {
         return false;
     }
-    if (bpf_map_update_elem(ctx->map_configuration,
-                            &map_key, config, 0) < 0) {
-        return false;
-    }
+
+    memcpy(ctx->mmap_configuration, config, sizeof(*config));
     return true;
 }
 
@@ -93,27 +161,19 @@ static bool ebpf_rss_set_indirections_table(struct 
EBPFRSSContext *ctx,
                                             uint16_t *indirections_table,
                                             size_t len)
 {
-    uint32_t i = 0;
-
     if (!ebpf_rss_is_loaded(ctx) || indirections_table == NULL ||
        len > VIRTIO_NET_RSS_MAX_TABLE_LEN) {
         return false;
     }
 
-    for (; i < len; ++i) {
-        if (bpf_map_update_elem(ctx->map_indirections_table, &i,
-                                indirections_table + i, 0) < 0) {
-            return false;
-        }
-    }
+    memcpy(ctx->mmap_indirections_table, indirections_table,
+            sizeof(*indirections_table) * len);
     return true;
 }
 
 static bool ebpf_rss_set_toepliz_key(struct EBPFRSSContext *ctx,
                                      uint8_t *toeplitz_key)
 {
-    uint32_t map_key = 0;
-
     /* prepare toeplitz key */
     uint8_t toe[VIRTIO_NET_RSS_MAX_KEY_SIZE] = {};
 
@@ -123,10 +183,7 @@ static bool ebpf_rss_set_toepliz_key(struct EBPFRSSContext 
*ctx,
     memcpy(toe, toeplitz_key, VIRTIO_NET_RSS_MAX_KEY_SIZE);
     *(uint32_t *)toe = ntohl(*(uint32_t *)toe);
 
-    if (bpf_map_update_elem(ctx->map_toeplitz_key, &map_key, toe,
-                            0) < 0) {
-        return false;
-    }
+    memcpy(ctx->mmap_toeplitz_key, toe, VIRTIO_NET_RSS_MAX_KEY_SIZE);
     return true;
 }
 
@@ -160,6 +217,20 @@ void ebpf_rss_unload(struct EBPFRSSContext *ctx)
         return;
     }
 
-    rss_bpf__destroy(ctx->obj);
+    ebpf_rss_munmap(ctx);
+
+    if (ctx->obj) {
+        rss_bpf__destroy(ctx->obj);
+    } else {
+        close(ctx->program_fd);
+        close(ctx->map_configuration);
+        close(ctx->map_toeplitz_key);
+        close(ctx->map_indirections_table);
+    }
+
     ctx->obj = NULL;
+    ctx->program_fd = -1;
+    ctx->map_configuration = -1;
+    ctx->map_toeplitz_key = -1;
+    ctx->map_indirections_table = -1;
 }
diff --git a/ebpf/ebpf_rss.h b/ebpf/ebpf_rss.h
index bf3f2572c7c..ab08a7266d0 100644
--- a/ebpf/ebpf_rss.h
+++ b/ebpf/ebpf_rss.h
@@ -20,6 +20,11 @@ struct EBPFRSSContext {
     int map_configuration;
     int map_toeplitz_key;
     int map_indirections_table;
+
+    /* mapped eBPF maps for direct access to omit bpf_map_update_elem() */
+    void *mmap_configuration;
+    void *mmap_toeplitz_key;
+    void *mmap_indirections_table;
 };
 
 struct EBPFRSSConfig {
-- 
2.39.1