Re: [RFC PATCH 4/5] qmp: Added new command to retrieve eBPF blob.

[Andrew Melnichenko]

Hi all,

On Thu, Mar 30, 2023 at 11:39 AM Daniel P. Berrangé <berrange@redhat.com> wrote:
>
> On Thu, Mar 30, 2023 at 03:15:21AM +0300, Andrew Melnychenko wrote:
> > 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.
> >
> > Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
> > ---
> >  monitor/qmp-cmds.c | 17 +++++++++++++++++
> >  qapi/misc.json     | 25 +++++++++++++++++++++++++
> >  2 files changed, 42 insertions(+)
> >
> > diff --git a/monitor/qmp-cmds.c b/monitor/qmp-cmds.c
> > index b0f948d337..8f2fc3e7ec 100644
> > --- a/monitor/qmp-cmds.c
> > +++ b/monitor/qmp-cmds.c
> > @@ -32,6 +32,7 @@
> >  #include "hw/mem/memory-device.h"
> >  #include "hw/intc/intc.h"
> >  #include "hw/rdma/rdma.h"
> > +#include "ebpf/ebpf.h"
> >
> >  NameInfo *qmp_query_name(Error **errp)
> >  {
> > @@ -209,3 +210,19 @@ static void __attribute__((__constructor__)) 
> > monitor_init_qmp_commands(void)
> >                           qmp_marshal_qmp_capabilities,
> >                           QCO_ALLOW_PRECONFIG, 0);
> >  }
> > +
> > +EbpfObject *qmp_request_ebpf(const char *id, Error **errp)
> > +{
> > +    EbpfObject *ret = NULL;
> > +    size_t size = 0;
> > +    const guchar *data = ebpf_find_binary_by_id(id, &size);
>
> "const void *data"  I believe
>
> > +
> > +    if (data) {
> > +        ret = g_new0(EbpfObject, 1);
> > +        ret->object = g_base64_encode(data, size);
> > +    } else {
> > +        error_setg(errp, "can't find eBPF object with id: %s", id);
>
> I think I'm inclined to say that we should add an 'Error **errp'
> parameter to ebpf_find_binary_by_id(), and make it responsible
> for this error message, such that we get

Ok, I'll add it.

>
>    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;
>
> > +    }
> > +
> > +    return ret;
> > +}
> > diff --git a/qapi/misc.json b/qapi/misc.json
> > index 6ddd16ea28..4689802460 100644
> > --- a/qapi/misc.json
> > +++ b/qapi/misc.json
> > @@ -618,3 +618,28 @@
> >  { 'event': 'VFU_CLIENT_HANGUP',
> >    'data': { 'vfu-id': 'str', 'vfu-qom-path': 'str',
> >              'dev-id': 'str', 'dev-qom-path': 'str' } }
> > +
> > +##
> > +# @EbpfObject:
> > +#
> > +# Structure that holds eBPF ELF object encoded in base64.
>
> Needs a 'Since' tag

Ah yes, thank you.

>
> > +##
> > +{ 'struct': 'EbpfObject',
> > +  'data': {'object': 'str'} }
> > +
> > +##
> > +# @request-ebpf:
> > +#
> > +# Function returns eBPF object that can be loaded with libbpf.
> > +# Management applications (g.e. libvirt) may load it and pass file
> > +# descriptors to QEMU. Which allows running QEMU without BPF capabilities.
> > +#
> > +# Returns: RSS eBPF object encoded in base64.
> > +#
> > +# Since: 7.3
>
> We're about to release 8.0 and so the next will be 8.1

Thanks, I'll update it.

>
> > +#
> > +##
> > +{ 'command': 'request-ebpf',
> > +  'data': { 'id': 'str' },
> > +  'returns': 'EbpfObject' }
>
> With regards,
> Daniel
> --
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>