Commit message style nitpick:
qmp: Add command to retrieve eBPF blob
or
qmp: New command to retrieve eBPF blob
It's a title, not a sentence.
Andrew Melnychenko <and...@daynix.com> writes:
> Now, the binary objects may be retrieved by id.
> It would require for future qmp commands that may require specific
> eBPF blob.
>
> Added command "request-ebpf". This command returns
> eBPF program encoded base64. The program taken from the
> skeleton and essentially is an ELF object that can be
> loaded in the future with libbpf.
>
> The reason to use the command to provide the eBPF object
> instead of a separate artifact was to avoid issues related
> to finding the eBPF itself. eBPF object is an ELF binary
> that contains the eBPF program and eBPF map description(BTF).
> Overall, eBPF object should contain the program and enough
> metadata to create/load eBPF with libbpf. As the eBPF
> maps/program should correspond to QEMU, the eBPF can't
> be used from different QEMU build.
>
> The first solution was a helper that comes with QEMU
> and loads appropriate eBPF objects. And the issue is
> to find a proper helper if the system has several
> different QEMUs installed and/or built from the source,
> which helpers may not be compatible.
>
> Another issue is QEMU updating while there is a running
> QEMU instance. With an updated helper, it may not be
> possible to hotplug virtio-net device to the already
> running QEMU. Overall, requesting the eBPF object from
> QEMU itself solves possible failures with acceptable effort.
>
> Links:
> [PATCH 3/5] qmp: Added the helper stamp check.
> https://lore.kernel.org/all/20230219162100.174318-4-and...@daynix.com/
>
> Signed-off-by: Andrew Melnychenko <and...@daynix.com>
> ---
> ebpf/ebpf.c | 69 +++++++++++++++++++++++++++++++++++++++++++
> ebpf/ebpf.h | 29 ++++++++++++++++++
> ebpf/ebpf_rss.c | 6 ++++
> ebpf/meson.build | 2 +-
> qapi/ebpf.json | 66 +++++++++++++++++++++++++++++++++++++++++
> qapi/meson.build | 1 +
> qapi/qapi-schema.json | 1 +
> 7 files changed, 173 insertions(+), 1 deletion(-)
> create mode 100644 ebpf/ebpf.c
> create mode 100644 ebpf/ebpf.h
> create mode 100644 qapi/ebpf.json
>
> diff --git a/ebpf/ebpf.c b/ebpf/ebpf.c
> new file mode 100644
> index 0000000000..2d73beb479
> --- /dev/null
> +++ b/ebpf/ebpf.c
> @@ -0,0 +1,69 @@
> +/*
> + * QEMU eBPF binary declaration routine.
> + *
> + * Developed by Daynix Computing LTD (http://www.daynix.com)
> + *
> + * Authors:
> + * Andrew Melnychenko <and...@daynix.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/queue.h"
> +#include "qapi/error.h"
> +#include "qapi/qapi-commands-ebpf.h"
> +#include "ebpf/ebpf.h"
> +
> +typedef struct ElfBinaryDataEntry {
> + int id;
> + const void *data;
> + size_t datalen;
> +
> + QSLIST_ENTRY(ElfBinaryDataEntry) node;
> +} ElfBinaryDataEntry;
> +
> +static QSLIST_HEAD(, ElfBinaryDataEntry) ebpf_elf_obj_list =
> + QSLIST_HEAD_INITIALIZER();
> +
> +void ebpf_register_binary_data(int id, const void *data, size_t datalen)
> +{
> + struct ElfBinaryDataEntry *dataentry = NULL;
> +
> + dataentry = g_new0(struct ElfBinaryDataEntry, 1);
> + dataentry->data = data;
> + dataentry->datalen = datalen;
> + dataentry->id = id;
> +
> + QSLIST_INSERT_HEAD(&ebpf_elf_obj_list, dataentry, node);
> +}
> +
> +const void *ebpf_find_binary_by_id(int id, size_t *sz, Error **errp)
> +{
> + struct ElfBinaryDataEntry *it = NULL;
> + QSLIST_FOREACH(it, &ebpf_elf_obj_list, node) {
> + if (id == it->id) {
> + *sz = it->datalen;
> + return it->data;
> + }
> + }
> +
> + error_setg(errp, "can't find eBPF object with id: %d", id);
> +
> + return NULL;
> +}
> +
> +EbpfObject *qmp_request_ebpf(EbpfProgramID id, Error **errp)
> +{
> + EbpfObject *ret = NULL;
> + size_t size = 0;
> + const void *data = ebpf_find_binary_by_id(id, &size, errp);
> + if (!data) {
> + return NULL;
> + }
> +
> + ret = g_new0(EbpfObject, 1);
> + ret->object = g_base64_encode(data, size);
> +
> + return ret;
> +}
> diff --git a/ebpf/ebpf.h b/ebpf/ebpf.h
> new file mode 100644
> index 0000000000..378d4e9c70
> --- /dev/null
> +++ b/ebpf/ebpf.h
> @@ -0,0 +1,29 @@
> +/*
> + * QEMU eBPF binary declaration routine.
> + *
> + * Developed by Daynix Computing LTD (http://www.daynix.com)
> + *
> + * Authors:
> + * Andrew Melnychenko <and...@daynix.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#ifndef EBPF_H
> +#define EBPF_H
> +
> +
> +void ebpf_register_binary_data(int id, const void *data,
> + size_t datalen);
> +const void *ebpf_find_binary_by_id(int id, size_t *sz,
> + struct Error **errp);
> +
> +#define ebpf_binary_init(id, fn) \
> +static void __attribute__((constructor)) ebpf_binary_init_ ## fn(void) \
> +{ \
> + size_t datalen = 0; \
> + const void *data = fn(&datalen); \
> + ebpf_register_binary_data(id, data, datalen); \
> +}
> +
> +#endif /* EBPF_H */
> diff --git a/ebpf/ebpf_rss.c b/ebpf/ebpf_rss.c
> index 150aa40813..c8a68da2c5 100644
> --- a/ebpf/ebpf_rss.c
> +++ b/ebpf/ebpf_rss.c
> @@ -13,6 +13,8 @@
>
> #include "qemu/osdep.h"
> #include "qemu/error-report.h"
> +#include "qapi/qapi-types-misc.h"
> +#include "qapi/qapi-commands-ebpf.h"
>
> #include <bpf/libbpf.h>
> #include <bpf/bpf.h>
> @@ -21,6 +23,8 @@
>
> #include "ebpf/ebpf_rss.h"
> #include "ebpf/rss.bpf.skeleton.h"
> +#include "ebpf/ebpf.h"
> +
> #include "trace.h"
>
> void ebpf_rss_init(struct EBPFRSSContext *ctx)
> @@ -261,3 +265,5 @@ void ebpf_rss_unload(struct EBPFRSSContext *ctx)
> ctx->map_toeplitz_key = -1;
> ctx->map_indirections_table = -1;
> }
> +
> +ebpf_binary_init(EBPF_PROGRAMID_RSS, rss_bpf__elf_bytes)
> diff --git a/ebpf/meson.build b/ebpf/meson.build
> index 2f627d6c7d..c5bf9295a2 100644
> --- a/ebpf/meson.build
> +++ b/ebpf/meson.build
> @@ -1 +1 @@
> -system_ss.add(when: libbpf, if_true: files('ebpf_rss.c'), if_false:
> files('ebpf_rss-stub.c'))
> +common_ss.add(when: libbpf, if_true: files('ebpf.c', 'ebpf_rss.c'),
> if_false: files('ebpf_rss-stub.c'))
> diff --git a/qapi/ebpf.json b/qapi/ebpf.json
> new file mode 100644
> index 0000000000..f413d00154
> --- /dev/null
> +++ b/qapi/ebpf.json
> @@ -0,0 +1,66 @@
> +# -*- Mode: Python -*-
> +# vim: filetype=python
> +#
> +# This work is licensed under the terms of the GNU GPL, version 2 or later.
> +# See the COPYING file in the top-level directory.
> +
> +##
> +# = eBPF Objects
> +#
> +# eBPF object is an ELF binary that contains the eBPF
> +# program and eBPF map description(BTF). Overall, eBPF
> +# object should contain the program and enough metadata
> +# to create/load eBPF with libbpf. As the eBPF maps/program
> +# should correspond to QEMU, the eBPF can't be used from
> +# different QEMU build.
An introduction, nice!
Two spaces between sentences for consistency, please.
Wrap comment lines at column 70, like this:
# eBPF object is an ELF binary that contains the eBPF program and eBPF
# map description(BTF). Overall, eBPF object should contain the
# program and enough metadata to create/load eBPF with libbpf. As the
# eBPF maps/program should correspond to QEMU, the eBPF can't be used
# from different QEMU build.
> +#
> +# Currently, there is a possible eBPF for receive-side scaling (RSS).
> +#
> +##
> +
> +##
> +# @EbpfObject:
> +#
> +# An eBPF ELF object.
> +#
> +# @object: the eBPF object encoded in base64
> +#
> +# Since: 9.0
> +##
> +{ 'struct': 'EbpfObject',
> + 'data': {'object': 'str'},
> + 'if': 'CONFIG_EBPF' }
> +
> +##
> +# @EbpfProgramID:
> +#
> +# The eBPF programs that can be gotten with request-ebpf.
> +#
> +# @rss: Receive side scaling, technology that allows steering traffic
> +# between queues by calculation hash. Users may set up
> +# indirection table and hash/packet types configurations. Used
> +# with virtio-net.
> +#
> +# Since: 9.0
> +##
> +{ 'enum': 'EbpfProgramID',
> + 'if': 'CONFIG_EBPF',
> + 'data': [ { 'name': 'rss' } ] }
> +
> +##
> +# @request-ebpf:
> +#
> +# Retrieve an eBPF object that can be loaded with libbpf. Management
> +# applications (g.e. libvirt) may load it and pass file descriptors to
> +# QEMU, so they can run running QEMU without BPF capabilities.
> +#
> +# @id: The ID of the program to return.
> +#
> +# Returns: eBPF object encoded in base64.
> +#
> +# Since: 9.0
> +##
> +{ 'command': 'request-ebpf',
> + 'data': { 'id': 'EbpfProgramID' },
> + 'returns': 'EbpfObject',
> + 'if': 'CONFIG_EBPF' }
> diff --git a/qapi/meson.build b/qapi/meson.build
> index f81a37565c..375d564277 100644
> --- a/qapi/meson.build
> +++ b/qapi/meson.build
> @@ -33,6 +33,7 @@ qapi_all_modules = [
> 'crypto',
> 'cxl',
> 'dump',
> + 'ebpf',
> 'error',
> 'introspect',
> 'job',
> diff --git a/qapi/qapi-schema.json b/qapi/qapi-schema.json
> index c01ec335e6..8304d45625 100644
> --- a/qapi/qapi-schema.json
> +++ b/qapi/qapi-schema.json
> @@ -53,6 +53,7 @@
> { 'include': 'char.json' }
> { 'include': 'dump.json' }
> { 'include': 'net.json' }
> +{ 'include': 'ebpf.json' }
> { 'include': 'rdma.json' }
> { 'include': 'rocker.json' }
> { 'include': 'tpm.json' }
With the (minor) doc comment fixes:
Acked-by: Markus Armbruster <arm...@redhat.com>
