[PATCH v3 0/8] Report fatal errors from failure with pre-opened eBPF RSS FDs

[PATCH v3 0/8] Report fatal errors from failure with pre-opened eBPF RSS FDs

[Daniel P. Berrangé]

The virtio-net code for eBPF RSS is still ignoring errors when
failing to load the eBPF RSS program passed in by the mgmt app
via pre-opened FDs.

This series re-factors the eBPF common code so that it actually
reports using "Error" objects. Then it makes virtio-net treat
a failure to load pre-opened FDs as a fatal problem. When doing
speculative opening of eBPF FDs, QEMU merely prints a warning,
and allows the software fallback to continue.

Trace event coverage is significantly expanded to make this all
much more debuggable too.

Changed in v3:

 - Fixed bpf stubs for new Error **errp argument
 - Added fix for pre-existing flaw with libxdp build logic
   when bpf is disabled

Changed in v2:

 - Split 'ebpf_error' probe into multiple probes

Daniel P. Berrangé (8):
  net: fix build when libbpf is disabled, but libxdp is enabled
  hw/net: fix typo s/epbf/ebpf/ in virtio-net
  ebpf: drop redundant parameter checks in static methods
  ebpf: improve error trace events
  ebpf: add formal error reporting to all APIs
  hw/net: report errors from failing to use eBPF RSS FDs
  ebpf: improve trace event coverage to all key operations
  hw/net: improve tracing of eBPF RSS setup

 ebpf/ebpf_rss-stub.c |   8 +--
 ebpf/ebpf_rss.c      | 118 ++++++++++++++++++++++++++++---------------
 ebpf/ebpf_rss.h      |  10 ++--
 ebpf/trace-events    |   8 ++-
 hw/net/trace-events  |   8 +--
 hw/net/virtio-net.c  |  63 +++++++++++++++--------
 meson.build          |  10 +++-
 net/meson.build      |   2 +-
 8 files changed, 151 insertions(+), 76 deletions(-)

-- 
2.46.0

[PATCH v3 1/8] net: fix build when libbpf is disabled, but libxdp is enabled

[Daniel P. Berrangé]

The net/af-xdp.c code is enabled when the libxdp library is present,
however, it also has direct API calls to bpf_xdp_query_id &
bpf_xdp_detach which are provided by the libbpf library.

As a result if building with --disable-libbpf, but libxdp gets
auto-detected, we'll fail to link QEMU

  /usr/bin/ld: libcommon.a.p/net_af-xdp.c.o: undefined reference to symbol 'bpf_xdp_query_id@@LIBBPF_0.7.0'

There are two bugs here

 * Since we have direct libbpf API calls, when building
   net/af-xdp.c, we must tell meson that libbpf is a
   dependancy, so that we directly link to it, rather
   than relying on indirect linkage.

 * When must skip probing for libxdp at all, when libbpf
   is not found, raising an error if --enable-libxdp was
   given explicitly.

Fixes: cb039ef3d9e3112da01e1ecd9b136ac9809ef733
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 meson.build     | 10 ++++++++--
 net/meson.build |  2 +-
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/meson.build b/meson.build
index d26690ce20..a9dfa1f3a7 100644
--- a/meson.build
+++ b/meson.build
@@ -2164,8 +2164,14 @@ endif
 # libxdp
 libxdp = not_found
 if not get_option('af_xdp').auto() or have_system
-    libxdp = dependency('libxdp', required: get_option('af_xdp'),
-                        version: '>=1.4.0', method: 'pkg-config')
+    if libbpf.found()
+        libxdp = dependency('libxdp', required: get_option('af_xdp'),
+                            version: '>=1.4.0', method: 'pkg-config')
+    else
+        if get_option('af_xdp').enabled()
+            error('libxdp requested, but libbpf is not available')
+        endif
+    endif
 endif
 
 # libdw
diff --git a/net/meson.build b/net/meson.build
index e0cd71470e..bb97b4dcbe 100644
--- a/net/meson.build
+++ b/net/meson.build
@@ -39,7 +39,7 @@ if have_netmap
   system_ss.add(files('netmap.c'))
 endif
 
-system_ss.add(when: libxdp, if_true: files('af-xdp.c'))
+system_ss.add(when: [libxdp, libbpf], if_true: files('af-xdp.c'))
 
 if have_vhost_net_user
   system_ss.add(when: 'CONFIG_VIRTIO_NET', if_true: files('vhost-user.c'), if_false: files('vhost-user-stub.c'))
-- 
2.46.0

[PATCH v3 2/8] hw/net: fix typo s/epbf/ebpf/ in virtio-net

[Daniel P. Berrangé]

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 hw/net/virtio-net.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index fb84d142ee..7c050246ea 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1254,7 +1254,7 @@ static void rss_data_to_rss_config(struct VirtioNetRssData *data,
     config->default_queue = data->default_queue;
 }
 
-static bool virtio_net_attach_epbf_rss(VirtIONet *n)
+static bool virtio_net_attach_ebpf_rss(VirtIONet *n)
 {
     struct EBPFRSSConfig config = {};
 
@@ -1276,7 +1276,7 @@ static bool virtio_net_attach_epbf_rss(VirtIONet *n)
     return true;
 }
 
-static void virtio_net_detach_epbf_rss(VirtIONet *n)
+static void virtio_net_detach_ebpf_rss(VirtIONet *n)
 {
     virtio_net_attach_ebpf_to_backend(n->nic, -1);
 }
@@ -1286,8 +1286,8 @@ static void virtio_net_commit_rss_config(VirtIONet *n)
     if (n->rss_data.enabled) {
         n->rss_data.enabled_software_rss = n->rss_data.populate_hash;
         if (n->rss_data.populate_hash) {
-            virtio_net_detach_epbf_rss(n);
-        } else if (!virtio_net_attach_epbf_rss(n)) {
+            virtio_net_detach_ebpf_rss(n);
+        } else if (!virtio_net_attach_ebpf_rss(n)) {
             if (get_vhost_net(qemu_get_queue(n->nic)->peer)) {
                 warn_report("Can't load eBPF RSS for vhost");
             } else {
@@ -1300,7 +1300,7 @@ static void virtio_net_commit_rss_config(VirtIONet *n)
                                     n->rss_data.indirections_len,
                                     sizeof(n->rss_data.key));
     } else {
-        virtio_net_detach_epbf_rss(n);
+        virtio_net_detach_ebpf_rss(n);
         trace_virtio_net_rss_disable();
     }
 }
-- 
2.46.0

[PATCH v3 3/8] ebpf: drop redundant parameter checks in static methods

[Daniel P. Berrangé]

Various static methods have checks on their parameters which were
already checked immediately before the method was invoked. Drop
these redundat checks to simplify the following commit which adds
formal error reporting.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 ebpf/ebpf_rss.c | 32 +++++---------------------------
 1 file changed, 5 insertions(+), 27 deletions(-)

diff --git a/ebpf/ebpf_rss.c b/ebpf/ebpf_rss.c
index dcaa80f380..0c42355a93 100644
--- a/ebpf/ebpf_rss.c
+++ b/ebpf/ebpf_rss.c
@@ -49,10 +49,6 @@ bool ebpf_rss_is_loaded(struct EBPFRSSContext *ctx)
 
 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);
@@ -90,10 +86,6 @@ toeplitz_fail:
 
 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());
@@ -177,15 +169,10 @@ bool ebpf_rss_load_fds(struct EBPFRSSContext *ctx, int program_fd,
     return true;
 }
 
-static bool ebpf_rss_set_config(struct EBPFRSSContext *ctx,
+static void 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;
 }
 
 static bool ebpf_rss_set_indirections_table(struct EBPFRSSContext *ctx,
@@ -194,8 +181,7 @@ static bool ebpf_rss_set_indirections_table(struct EBPFRSSContext *ctx,
 {
     char *cursor = ctx->mmap_indirections_table;
 
-    if (!ebpf_rss_is_loaded(ctx) || indirections_table == NULL ||
-       len > VIRTIO_NET_RSS_MAX_TABLE_LEN) {
+    if (len > VIRTIO_NET_RSS_MAX_TABLE_LEN) {
         return false;
     }
 
@@ -207,20 +193,16 @@ static bool ebpf_rss_set_indirections_table(struct EBPFRSSContext *ctx,
     return true;
 }
 
-static bool ebpf_rss_set_toepliz_key(struct EBPFRSSContext *ctx,
+static void ebpf_rss_set_toepliz_key(struct EBPFRSSContext *ctx,
                                      uint8_t *toeplitz_key)
 {
     /* prepare toeplitz key */
     uint8_t toe[VIRTIO_NET_RSS_MAX_KEY_SIZE] = {};
 
-    if (!ebpf_rss_is_loaded(ctx) || toeplitz_key == NULL) {
-        return false;
-    }
     memcpy(toe, toeplitz_key, VIRTIO_NET_RSS_MAX_KEY_SIZE);
     *(uint32_t *)toe = ntohl(*(uint32_t *)toe);
 
     memcpy(ctx->mmap_toeplitz_key, toe, VIRTIO_NET_RSS_MAX_KEY_SIZE);
-    return true;
 }
 
 bool ebpf_rss_set_all(struct EBPFRSSContext *ctx, struct EBPFRSSConfig *config,
@@ -231,18 +213,14 @@ bool ebpf_rss_set_all(struct EBPFRSSContext *ctx, struct EBPFRSSConfig *config,
         return false;
     }
 
-    if (!ebpf_rss_set_config(ctx, config)) {
-        return false;
-    }
+    ebpf_rss_set_config(ctx, config);
 
     if (!ebpf_rss_set_indirections_table(ctx, indirections_table,
                                       config->indirections_len)) {
         return false;
     }
 
-    if (!ebpf_rss_set_toepliz_key(ctx, toeplitz_key)) {
-        return false;
-    }
+    ebpf_rss_set_toepliz_key(ctx, toeplitz_key);
 
     return true;
 }
-- 
2.46.0

[PATCH v3 4/8] ebpf: improve error trace events

[Daniel P. Berrangé]

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>
---
 ebpf/ebpf_rss.c   | 10 +++++-----
 ebpf/trace-events |  4 +++-
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/ebpf/ebpf_rss.c b/ebpf/ebpf_rss.c
index 0c42355a93..d39916b368 100644
--- a/ebpf/ebpf_rss.c
+++ b/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;
     }
 
diff --git a/ebpf/trace-events b/ebpf/trace-events
index b3ad1a35f2..a0f157be37 100644
--- a/ebpf/trace-events
+++ b/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"
-- 
2.46.0

[PATCH v3 5/8] ebpf: add formal error reporting to all APIs

[Daniel P. Berrangé]

The eBPF code is currently reporting error messages through trace
events. Trace events are fine for debugging, but they are not to be
considered the primary error reporting mechanism, as their output
is inaccessible to callers.

This adds an "Error **errp" parameter to all methods which have
important error scenarios to report to the caller.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 ebpf/ebpf_rss-stub.c |  8 +++---
 ebpf/ebpf_rss.c      | 59 +++++++++++++++++++++++++++++++++++---------
 ebpf/ebpf_rss.h      | 10 +++++---
 hw/net/virtio-net.c  |  7 +++---
 4 files changed, 64 insertions(+), 20 deletions(-)

diff --git a/ebpf/ebpf_rss-stub.c b/ebpf/ebpf_rss-stub.c
index 8d7fae2ad9..d0e7f99fb9 100644
--- a/ebpf/ebpf_rss-stub.c
+++ b/ebpf/ebpf_rss-stub.c
@@ -23,19 +23,21 @@ bool ebpf_rss_is_loaded(struct EBPFRSSContext *ctx)
     return false;
 }
 
-bool ebpf_rss_load(struct EBPFRSSContext *ctx)
+bool ebpf_rss_load(struct EBPFRSSContext *ctx, Error **errp)
 {
     return false;
 }
 
 bool ebpf_rss_load_fds(struct EBPFRSSContext *ctx, int program_fd,
-                       int config_fd, int toeplitz_fd, int table_fd)
+                       int config_fd, int toeplitz_fd, int table_fd,
+                       Error **errp)
 {
     return false;
 }
 
 bool ebpf_rss_set_all(struct EBPFRSSContext *ctx, struct EBPFRSSConfig *config,
-                      uint16_t *indirections_table, uint8_t *toeplitz_key)
+                      uint16_t *indirections_table, uint8_t *toeplitz_key,
+                      Error **errp)
 {
     return false;
 }
diff --git a/ebpf/ebpf_rss.c b/ebpf/ebpf_rss.c
index d39916b368..67cdab197d 100644
--- a/ebpf/ebpf_rss.c
+++ b/ebpf/ebpf_rss.c
@@ -47,13 +47,14 @@ bool ebpf_rss_is_loaded(struct EBPFRSSContext *ctx)
     return ctx != NULL && (ctx->obj != NULL || ctx->program_fd != -1);
 }
 
-static bool ebpf_rss_mmap(struct EBPFRSSContext *ctx)
+static bool ebpf_rss_mmap(struct EBPFRSSContext *ctx, Error **errp)
 {
     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_rss_mmap_error(ctx, "configuration");
+        error_setg(errp, "Unable to map eBPF configuration array");
         return false;
     }
     ctx->mmap_toeplitz_key = mmap(NULL, qemu_real_host_page_size(),
@@ -61,6 +62,7 @@ static bool ebpf_rss_mmap(struct EBPFRSSContext *ctx)
                                    ctx->map_toeplitz_key, 0);
     if (ctx->mmap_toeplitz_key == MAP_FAILED) {
         trace_ebpf_rss_mmap_error(ctx, "toeplitz key");
+        error_setg(errp, "Unable to map eBPF toeplitz array");
         goto toeplitz_fail;
     }
     ctx->mmap_indirections_table = mmap(NULL, qemu_real_host_page_size(),
@@ -68,6 +70,7 @@ static bool ebpf_rss_mmap(struct EBPFRSSContext *ctx)
                                    ctx->map_indirections_table, 0);
     if (ctx->mmap_indirections_table == MAP_FAILED) {
         trace_ebpf_rss_mmap_error(ctx, "indirections table");
+        error_setg(errp, "Unable to map eBPF indirection array");
         goto indirection_fail;
     }
 
@@ -95,7 +98,7 @@ static void ebpf_rss_munmap(struct EBPFRSSContext *ctx)
     ctx->mmap_indirections_table = NULL;
 }
 
-bool ebpf_rss_load(struct EBPFRSSContext *ctx)
+bool ebpf_rss_load(struct EBPFRSSContext *ctx, Error **errp)
 {
     struct rss_bpf *rss_bpf_ctx;
 
@@ -106,6 +109,7 @@ bool ebpf_rss_load(struct EBPFRSSContext *ctx)
     rss_bpf_ctx = rss_bpf__open();
     if (rss_bpf_ctx == NULL) {
         trace_ebpf_rss_open_error(ctx);
+        error_setg(errp, "Unable to open eBPF RSS object");
         goto error;
     }
 
@@ -113,6 +117,7 @@ bool ebpf_rss_load(struct EBPFRSSContext *ctx)
 
     if (rss_bpf__load(rss_bpf_ctx)) {
         trace_ebpf_rss_load_error(ctx);
+        error_setg(errp, "Unable to load eBPF program");
         goto error;
     }
 
@@ -126,7 +131,7 @@ 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)) {
+    if (!ebpf_rss_mmap(ctx, errp)) {
         goto error;
     }
 
@@ -143,13 +148,28 @@ error:
 }
 
 bool ebpf_rss_load_fds(struct EBPFRSSContext *ctx, int program_fd,
-                       int config_fd, int toeplitz_fd, int table_fd)
+                       int config_fd, int toeplitz_fd, int table_fd,
+                       Error **errp)
 {
     if (ebpf_rss_is_loaded(ctx)) {
+        error_setg(errp, "eBPF program is already loaded");
         return false;
     }
 
-    if (program_fd < 0 || config_fd < 0 || toeplitz_fd < 0 || table_fd < 0) {
+    if (program_fd < 0) {
+        error_setg(errp, "eBPF program FD is not open");
+        return false;
+    }
+    if (config_fd < 0) {
+        error_setg(errp, "eBPF config FD is not open");
+        return false;
+    }
+    if (toeplitz_fd < 0) {
+        error_setg(errp, "eBPF toeplitz FD is not open");
+        return false;
+    }
+    if (table_fd < 0) {
+        error_setg(errp, "eBPF indirection FD is not open");
         return false;
     }
 
@@ -158,7 +178,7 @@ bool ebpf_rss_load_fds(struct EBPFRSSContext *ctx, int program_fd,
     ctx->map_toeplitz_key = toeplitz_fd;
     ctx->map_indirections_table = table_fd;
 
-    if (!ebpf_rss_mmap(ctx)) {
+    if (!ebpf_rss_mmap(ctx, errp)) {
         ctx->program_fd = -1;
         ctx->map_configuration = -1;
         ctx->map_toeplitz_key = -1;
@@ -177,11 +197,14 @@ static void ebpf_rss_set_config(struct EBPFRSSContext *ctx,
 
 static bool ebpf_rss_set_indirections_table(struct EBPFRSSContext *ctx,
                                             uint16_t *indirections_table,
-                                            size_t len)
+                                            size_t len,
+                                            Error **errp)
 {
     char *cursor = ctx->mmap_indirections_table;
 
     if (len > VIRTIO_NET_RSS_MAX_TABLE_LEN) {
+        error_setg(errp, "Indirections table length %zu exceeds limit %d",
+                   len, VIRTIO_NET_RSS_MAX_TABLE_LEN);
         return false;
     }
 
@@ -206,17 +229,31 @@ static void ebpf_rss_set_toepliz_key(struct EBPFRSSContext *ctx,
 }
 
 bool ebpf_rss_set_all(struct EBPFRSSContext *ctx, struct EBPFRSSConfig *config,
-                      uint16_t *indirections_table, uint8_t *toeplitz_key)
+                      uint16_t *indirections_table, uint8_t *toeplitz_key,
+                      Error **errp)
 {
-    if (!ebpf_rss_is_loaded(ctx) || config == NULL ||
-        indirections_table == NULL || toeplitz_key == NULL) {
+    if (!ebpf_rss_is_loaded(ctx)) {
+        error_setg(errp, "eBPF program is not loaded");
+        return false;
+    }
+    if (config == NULL) {
+        error_setg(errp, "eBPF config table is NULL");
+        return false;
+    }
+    if (indirections_table == NULL) {
+        error_setg(errp, "eBPF indirections table is NULL");
+        return false;
+    }
+    if (toeplitz_key == NULL) {
+        error_setg(errp, "eBPF toeplitz key is NULL");
         return false;
     }
 
     ebpf_rss_set_config(ctx, config);
 
     if (!ebpf_rss_set_indirections_table(ctx, indirections_table,
-                                      config->indirections_len)) {
+                                         config->indirections_len,
+                                         errp)) {
         return false;
     }
 
diff --git a/ebpf/ebpf_rss.h b/ebpf/ebpf_rss.h
index 239242b0d2..86a5787789 100644
--- a/ebpf/ebpf_rss.h
+++ b/ebpf/ebpf_rss.h
@@ -14,6 +14,8 @@
 #ifndef QEMU_EBPF_RSS_H
 #define QEMU_EBPF_RSS_H
 
+#include "qapi/error.h"
+
 #define EBPF_RSS_MAX_FDS 4
 
 struct EBPFRSSContext {
@@ -41,13 +43,15 @@ void ebpf_rss_init(struct EBPFRSSContext *ctx);
 
 bool ebpf_rss_is_loaded(struct EBPFRSSContext *ctx);
 
-bool ebpf_rss_load(struct EBPFRSSContext *ctx);
+bool ebpf_rss_load(struct EBPFRSSContext *ctx, Error **errp);
 
 bool ebpf_rss_load_fds(struct EBPFRSSContext *ctx, int program_fd,
-                       int config_fd, int toeplitz_fd, int table_fd);
+                       int config_fd, int toeplitz_fd, int table_fd,
+                       Error **errp);
 
 bool ebpf_rss_set_all(struct EBPFRSSContext *ctx, struct EBPFRSSConfig *config,
-                      uint16_t *indirections_table, uint8_t *toeplitz_key);
+                      uint16_t *indirections_table, uint8_t *toeplitz_key,
+                      Error **errp);
 
 void ebpf_rss_unload(struct EBPFRSSContext *ctx);
 
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 7c050246ea..289fba8152 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1265,7 +1265,8 @@ static bool virtio_net_attach_ebpf_rss(VirtIONet *n)
     rss_data_to_rss_config(&n->rss_data, &config);
 
     if (!ebpf_rss_set_all(&n->ebpf_rss, &config,
-                          n->rss_data.indirections_table, n->rss_data.key)) {
+                          n->rss_data.indirections_table, n->rss_data.key,
+                          NULL)) {
         return false;
     }
 
@@ -1336,7 +1337,7 @@ static bool virtio_net_load_ebpf_fds(VirtIONet *n)
         }
     }
 
-    ret = ebpf_rss_load_fds(&n->ebpf_rss, fds[0], fds[1], fds[2], fds[3]);
+    ret = ebpf_rss_load_fds(&n->ebpf_rss, fds[0], fds[1], fds[2], fds[3], NULL);
 
 exit:
     if (!ret) {
@@ -1354,7 +1355,7 @@ static bool virtio_net_load_ebpf(VirtIONet *n)
 
     if (virtio_net_attach_ebpf_to_backend(n->nic, -1)) {
         if (!(n->ebpf_rss_fds && virtio_net_load_ebpf_fds(n))) {
-            ret = ebpf_rss_load(&n->ebpf_rss);
+            ret = ebpf_rss_load(&n->ebpf_rss, NULL);
         }
     }
 
-- 
2.46.0

[PATCH v3 6/8] hw/net: report errors from failing to use eBPF RSS FDs

[Daniel P. Berrangé]

If the user/mgmt app passed in a set of pre-opened FDs for eBPF RSS,
then it is expecting QEMU to use them. Any failure to do so must be
considered a fatal error and propagated back up the stack, otherwise
deployment mistakes will not be detectable in a prompt manner. When
not using pre-opened FDs, then eBPF RSS is tried on a "best effort"
basis only and thus fallback to software RSS is valid.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 hw/net/virtio-net.c | 41 +++++++++++++++++++++++++++++------------
 1 file changed, 29 insertions(+), 12 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 289fba8152..c08ae55424 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1316,28 +1316,27 @@ static void virtio_net_disable_rss(VirtIONet *n)
     virtio_net_commit_rss_config(n);
 }
 
-static bool virtio_net_load_ebpf_fds(VirtIONet *n)
+static bool virtio_net_load_ebpf_fds(VirtIONet *n, Error **errp)
 {
     int fds[EBPF_RSS_MAX_FDS] = { [0 ... EBPF_RSS_MAX_FDS - 1] = -1};
     int ret = true;
     int i = 0;
 
     if (n->nr_ebpf_rss_fds != EBPF_RSS_MAX_FDS) {
-        warn_report("Expected %d file descriptors but got %d",
-                    EBPF_RSS_MAX_FDS, n->nr_ebpf_rss_fds);
-       return false;
-   }
+        error_setg(errp, "Expected %d file descriptors but got %d",
+                   EBPF_RSS_MAX_FDS, n->nr_ebpf_rss_fds);
+        return false;
+    }
 
     for (i = 0; i < n->nr_ebpf_rss_fds; i++) {
-        fds[i] = monitor_fd_param(monitor_cur(), n->ebpf_rss_fds[i],
-                                  &error_warn);
+        fds[i] = monitor_fd_param(monitor_cur(), n->ebpf_rss_fds[i], errp);
         if (fds[i] < 0) {
             ret = false;
             goto exit;
         }
     }
 
-    ret = ebpf_rss_load_fds(&n->ebpf_rss, fds[0], fds[1], fds[2], fds[3], NULL);
+    ret = ebpf_rss_load_fds(&n->ebpf_rss, fds[0], fds[1], fds[2], fds[3], errp);
 
 exit:
     if (!ret) {
@@ -1349,13 +1348,15 @@ exit:
     return ret;
 }
 
-static bool virtio_net_load_ebpf(VirtIONet *n)
+static bool virtio_net_load_ebpf(VirtIONet *n, Error **errp)
 {
     bool ret = false;
 
     if (virtio_net_attach_ebpf_to_backend(n->nic, -1)) {
-        if (!(n->ebpf_rss_fds && virtio_net_load_ebpf_fds(n))) {
-            ret = ebpf_rss_load(&n->ebpf_rss, NULL);
+        if (n->ebpf_rss_fds) {
+            ret = virtio_net_load_ebpf_fds(n, errp);
+        } else {
+            ret = ebpf_rss_load(&n->ebpf_rss, errp);
         }
     }
 
@@ -3761,7 +3762,23 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
     net_rx_pkt_init(&n->rx_pkt);
 
     if (virtio_has_feature(n->host_features, VIRTIO_NET_F_RSS)) {
-        virtio_net_load_ebpf(n);
+        Error *err = NULL;
+        if (!virtio_net_load_ebpf(n, &err)) {
+            /*
+             * If user explicitly gave QEMU RSS FDs to use, then
+             * failing to use them must be considered a fatal
+             * error. If no RSS FDs were provided, QEMU is trying
+             * eBPF on a "best effort" basis only, so report a
+             * warning and allow fallback to software RSS.
+             */
+            if (n->ebpf_rss_fds) {
+                error_propagate(errp, err);
+            } else {
+                warn_report("unable to load eBPF RSS: %s",
+                            error_get_pretty(err));
+                error_free(err);
+            }
+        }
     }
 }
 
-- 
2.46.0

[PATCH v3 7/8] ebpf: improve trace event coverage to all key operations

[Daniel P. Berrangé]

The existing error trace event is renamed to have a name prefix
matching its source file & to remove the redundant first arg that
adds no useful information.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 ebpf/ebpf_rss.c   | 19 +++++++++++++++++++
 ebpf/trace-events |  4 ++++
 2 files changed, 23 insertions(+)

diff --git a/ebpf/ebpf_rss.c b/ebpf/ebpf_rss.c
index 67cdab197d..e793786c17 100644
--- a/ebpf/ebpf_rss.c
+++ b/ebpf/ebpf_rss.c
@@ -74,6 +74,10 @@ static bool ebpf_rss_mmap(struct EBPFRSSContext *ctx, Error **errp)
         goto indirection_fail;
     }
 
+    trace_ebpf_rss_mmap(ctx,
+                        ctx->mmap_configuration,
+                        ctx->mmap_toeplitz_key,
+                        ctx->mmap_indirections_table);
     return true;
 
 indirection_fail:
@@ -131,6 +135,11 @@ bool ebpf_rss_load(struct EBPFRSSContext *ctx, Error **errp)
     ctx->map_toeplitz_key = bpf_map__fd(
             rss_bpf_ctx->maps.tap_rss_map_toeplitz_key);
 
+    trace_ebpf_rss_load(ctx,
+                        ctx->program_fd,
+                        ctx->map_configuration,
+                        ctx->map_indirections_table,
+                        ctx->map_toeplitz_key);
     if (!ebpf_rss_mmap(ctx, errp)) {
         goto error;
     }
@@ -178,6 +187,12 @@ bool ebpf_rss_load_fds(struct EBPFRSSContext *ctx, int program_fd,
     ctx->map_toeplitz_key = toeplitz_fd;
     ctx->map_indirections_table = table_fd;
 
+    trace_ebpf_rss_load(ctx,
+                        ctx->program_fd,
+                        ctx->map_configuration,
+                        ctx->map_indirections_table,
+                        ctx->map_toeplitz_key);
+
     if (!ebpf_rss_mmap(ctx, errp)) {
         ctx->program_fd = -1;
         ctx->map_configuration = -1;
@@ -259,6 +274,8 @@ bool ebpf_rss_set_all(struct EBPFRSSContext *ctx, struct EBPFRSSConfig *config,
 
     ebpf_rss_set_toepliz_key(ctx, toeplitz_key);
 
+    trace_ebpf_rss_set_data(ctx, config, indirections_table, toeplitz_key);
+
     return true;
 }
 
@@ -268,6 +285,8 @@ void ebpf_rss_unload(struct EBPFRSSContext *ctx)
         return;
     }
 
+    trace_ebpf_rss_unload(ctx);
+
     ebpf_rss_munmap(ctx);
 
     if (ctx->obj) {
diff --git a/ebpf/trace-events b/ebpf/trace-events
index a0f157be37..bf3d9b6451 100644
--- a/ebpf/trace-events
+++ b/ebpf/trace-events
@@ -1,6 +1,10 @@
 # See docs/devel/tracing.rst for syntax documentation.
 
 # ebpf-rss.c
+ebpf_rss_load(void *ctx, int progfd, int cfgfd, int toepfd, int indirfd) "ctx=%p program-fd=%d config-fd=%d toeplitz-fd=%d indirection-fd=%d"
 ebpf_rss_load_error(void *ctx) "ctx=%p"
+ebpf_rss_mmap(void *ctx, void *cfgptr, void *toepptr, void *indirptr) "ctx=%p config-ptr=%p toeplitz-ptr=%p indirection-ptr=%p"
 ebpf_rss_mmap_error(void *ctx, const char *object) "ctx=%p object=%s"
 ebpf_rss_open_error(void *ctx) "ctx=%p"
+ebpf_rss_set_data(void *ctx, void *cfgptr, void *toepptr, void *indirptr) "ctx=%p config-ptr=%p toeplitz-ptr=%p indirection-ptr=%p"
+ebpf_rss_unload(void *ctx) "rss unload ctx=%p"
-- 
2.46.0

[PATCH v3 8/8] hw/net: improve tracing of eBPF RSS setup

[Daniel P. Berrangé]

This adds more trace events to key eBPF RSS setup operations, and
also distinguishes events from multiple NIC instances.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 hw/net/trace-events | 8 +++++---
 hw/net/virtio-net.c | 9 ++++++---
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/hw/net/trace-events b/hw/net/trace-events
index 4c6687923e..91a3d0c054 100644
--- a/hw/net/trace-events
+++ b/hw/net/trace-events
@@ -394,9 +394,11 @@ virtio_net_announce_notify(void) ""
 virtio_net_announce_timer(int round) "%d"
 virtio_net_handle_announce(int round) "%d"
 virtio_net_post_load_device(void)
-virtio_net_rss_disable(void)
-virtio_net_rss_error(const char *msg, uint32_t value) "%s, value 0x%08x"
-virtio_net_rss_enable(uint32_t p1, uint16_t p2, uint8_t p3) "hashes 0x%x, table of %d, key of %d"
+virtio_net_rss_load(void *nic, size_t nfds, void *fds) "nic=%p nfds=%zu fds=%p"
+virtio_net_rss_attach_ebpf(void *nic, int prog_fd) "nic=%p prog-fd=%d"
+virtio_net_rss_disable(void *nic) "nic=%p"
+virtio_net_rss_error(void *nic, const char *msg, uint32_t value) "nic=%p msg=%s, value 0x%08x"
+virtio_net_rss_enable(void *nic, uint32_t p1, uint16_t p2, uint8_t p3) "nic=%p hashes 0x%x, table of %d, key of %d"
 
 # tulip.c
 tulip_reg_write(uint64_t addr, const char *name, int size, uint64_t val) "addr 0x%02"PRIx64" (%s) size %d value 0x%08"PRIx64
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index c08ae55424..60e19bffcb 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1241,6 +1241,7 @@ static bool virtio_net_attach_ebpf_to_backend(NICState *nic, int prog_fd)
         return false;
     }
 
+    trace_virtio_net_rss_attach_ebpf(nic, prog_fd);
     return nc->info->set_steering_ebpf(nc, prog_fd);
 }
 
@@ -1297,12 +1298,13 @@ static void virtio_net_commit_rss_config(VirtIONet *n)
             }
         }
 
-        trace_virtio_net_rss_enable(n->rss_data.hash_types,
+        trace_virtio_net_rss_enable(n,
+                                    n->rss_data.hash_types,
                                     n->rss_data.indirections_len,
                                     sizeof(n->rss_data.key));
     } else {
         virtio_net_detach_ebpf_rss(n);
-        trace_virtio_net_rss_disable();
+        trace_virtio_net_rss_disable(n);
     }
 }
 
@@ -1353,6 +1355,7 @@ static bool virtio_net_load_ebpf(VirtIONet *n, Error **errp)
     bool ret = false;
 
     if (virtio_net_attach_ebpf_to_backend(n->nic, -1)) {
+        trace_virtio_net_rss_load(n, n->nr_ebpf_rss_fds, n->ebpf_rss_fds);
         if (n->ebpf_rss_fds) {
             ret = virtio_net_load_ebpf_fds(n, errp);
         } else {
@@ -1484,7 +1487,7 @@ static uint16_t virtio_net_handle_rss(VirtIONet *n,
     virtio_net_commit_rss_config(n);
     return queue_pairs;
 error:
-    trace_virtio_net_rss_error(err_msg, err_value);
+    trace_virtio_net_rss_error(n, err_msg, err_value);
     virtio_net_disable_rss(n);
     return 0;
 }
-- 
2.46.0