[RFC PATCH 1/5] ebpf: Added eBPF initialization by fds and map update.

[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@xxxxxxxxxx>
---
 ebpf/ebpf_rss-stub.c |   6 +++
 ebpf/ebpf_rss.c      | 120 ++++++++++++++++++++++++++++++++++---------
 ebpf/ebpf_rss.h      |  10 ++++
 3 files changed, 113 insertions(+), 23 deletions(-)

diff --git a/ebpf/ebpf_rss-stub.c b/ebpf/ebpf_rss-stub.c
index e71e229190..8d7fae2ad9 100644
--- a/ebpf/ebpf_rss-stub.c
+++ b/ebpf/ebpf_rss-stub.c
@@ -28,6 +28,12 @@ bool ebpf_rss_load(struct EBPFRSSContext *ctx)
     return false;
 }
 
+bool ebpf_rss_load_fds(struct EBPFRSSContext *ctx, int program_fd,
+                       int config_fd, int toeplitz_fd, int table_fd)
+{
+    return false;
+}
+
 bool ebpf_rss_set_all(struct EBPFRSSContext *ctx, struct EBPFRSSConfig *config,
                       uint16_t *indirections_table, uint8_t *toeplitz_key)
 {
diff --git a/ebpf/ebpf_rss.c b/ebpf/ebpf_rss.c
index cee658c158..08015fecb1 100644
--- a/ebpf/ebpf_rss.c
+++ b/ebpf/ebpf_rss.c
@@ -27,19 +27,68 @@ void ebpf_rss_init(struct EBPFRSSContext *ctx)
 {
     if (ctx != NULL) {
         ctx->obj = NULL;
+        ctx->program_fd = -1;
     }
 }
 
 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());
+    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());
 }
 
 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;
     }
 
@@ -66,26 +115,51 @@ 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;
 
     return false;
 }
 
-static bool ebpf_rss_set_config(struct EBPFRSSContext *ctx,
-                                struct EBPFRSSConfig *config)
+bool ebpf_rss_load_fds(struct EBPFRSSContext *ctx, int program_fd,
+                       int config_fd, int toeplitz_fd, int table_fd)
 {
-    uint32_t map_key = 0;
+    if (ctx == NULL || ebpf_rss_is_loaded(ctx)) {
+        return false;
+    }
 
-    if (!ebpf_rss_is_loaded(ctx)) {
+    if (program_fd < 0 || config_fd < 0 || toeplitz_fd < 0 || table_fd < 0) {
         return false;
     }
-    if (bpf_map_update_elem(ctx->map_configuration,
-                            &map_key, config, 0) < 0) {
+
+    ctx->program_fd = program_fd;
+    ctx->map_configuration = config_fd;
+    ctx->map_toeplitz_key = toeplitz_fd;
+    ctx->map_indirections_table = table_fd;
+
+    if (!ebpf_rss_mmap(ctx)) {
+        ctx->program_fd = -1;
         return false;
     }
+
+    return true;
+}
+
+static bool ebpf_rss_set_config(struct EBPFRSSContext *ctx,
+                                struct EBPFRSSConfig *config)
+{
+    if (!ebpf_rss_is_loaded(ctx)) {
+        return false;
+    }
+
+    memcpy(ctx->mmap_configuration, config, sizeof(*config));
     return true;
 }
 
@@ -93,27 +167,19 @@ 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 +189,7 @@ 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 +223,17 @@ 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;
 }
diff --git a/ebpf/ebpf_rss.h b/ebpf/ebpf_rss.h
index bf3f2572c7..239242b0d2 100644
--- a/ebpf/ebpf_rss.h
+++ b/ebpf/ebpf_rss.h
@@ -14,12 +14,19 @@
 #ifndef QEMU_EBPF_RSS_H
 #define QEMU_EBPF_RSS_H
 
+#define EBPF_RSS_MAX_FDS 4
+
 struct EBPFRSSContext {
     void *obj;
     int program_fd;
     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 {
@@ -36,6 +43,9 @@ bool ebpf_rss_is_loaded(struct EBPFRSSContext *ctx);
 
 bool ebpf_rss_load(struct EBPFRSSContext *ctx);
 
+bool ebpf_rss_load_fds(struct EBPFRSSContext *ctx, int program_fd,
+                       int config_fd, int toeplitz_fd, int table_fd);
+
 bool ebpf_rss_set_all(struct EBPFRSSContext *ctx, struct EBPFRSSConfig *config,
                       uint16_t *indirections_table, uint8_t *toeplitz_key);
 
-- 
2.39.1