Re: [Qemu-devel] [PATCH PULL 02/31] contrib/rdmacm-mux: Add implementation of RDMA User MAD multiplexer

[Cornelia Huck <cohuck@redhat.com>]

On Mon, 7 Jan 2019 19:28:10 +0200
Marcel Apfelbaum <marcel.apfelbaum@gmail.com> wrote:

> On 1/3/19 12:34 PM, Cornelia Huck wrote:
> > On Sat, 22 Dec 2018 11:50:07 +0200
> > Marcel Apfelbaum <marcel.apfelbaum@gmail.com> wrote:
> >  
> >> From: Yuval Shaia <yuval.shaia@oracle.com>
> >>
> >> RDMA MAD kernel module (ibcm) disallow more than one MAD-agent for a
> >> given MAD class.
> >> This does not go hand-by-hand with qemu pvrdma device's requirements
> >> where each VM is MAD agent.
> >> Fix it by adding implementation of RDMA MAD multiplexer service which on
> >> one hand register as a sole MAD agent with the kernel module and on the
> >> other hand gives service to more than one VM.
> >>
> >> Design Overview:
> >> Reviewed-by: Shamir Rabinovitch <shamir.rabinovitch@oracle.com>
> >> ----------------
> >> A server process is registered to UMAD framework (for this to work the
> >> rdma_cm kernel module needs to be unloaded) and creates a unix socket to
> >> listen to incoming request from clients.
> >> A client process (such as QEMU) connects to this unix socket and
> >> registers with its own GID.
> >>
> >> TX:
> >> ----
> >> When client needs to send rdma_cm MAD message it construct it the same
> >> way as without this multiplexer, i.e. creates a umad packet but this
> >> time it writes its content to the socket instead of calling umad_send().
> >> The server, upon receiving such a message fetch local_comm_id from it so
> >> a context for this session can be maintain and relay the message to UMAD
> >> layer by calling umad_send().
> >>
> >> RX:
> >> ----
> >> The server creates a worker thread to process incoming rdma_cm MAD
> >> messages. When an incoming message arrived (umad_recv()) the server,
> >> depending on the message type (attr_id) looks for target client by
> >> either searching in gid->fd table or in local_comm_id->fd table. With
> >> the extracted fd the server relays to incoming message to the client.
> >>
> >> Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
> >> Reviewed-by: Shamir Rabinovitch <shamir.rabinovitch@oracle.com>
> >> Signed-off-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> >>
> >> Signed-off-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> >> ---
> >>   MAINTAINERS                      |   1 +
> >>   Makefile                         |   3 +
> >>   Makefile.objs                    |   1 +
> >>   contrib/rdmacm-mux/Makefile.objs |   4 +
> >>   contrib/rdmacm-mux/main.c        | 798 +++++++++++++++++++++++++++++++
> >>   contrib/rdmacm-mux/rdmacm-mux.h  |  61 +++
> >>   6 files changed, 868 insertions(+)
> >>   create mode 100644 contrib/rdmacm-mux/Makefile.objs
> >>   create mode 100644 contrib/rdmacm-mux/main.c
> >>   create mode 100644 contrib/rdmacm-mux/rdmacm-mux.h  
> > This commit breaks building with clang on Fedora 28 for me; I get a
> > bunch of
> >  
> 
> Hi Cornelia,
> Thanks for spotting the issue.
> 
> > clang-6.0: error: -libumad: 'linker' input unused [-Werror,-Wunused-command-line-argument]  
> 
> Is really strange, the rdma-mux is part of the contrib directory
> and is not even compiled by default.
> 
> > Explicitly passing --disable-pvrdma to configure disables the offending
> > code.
> >
> > Let me know if you need more information.  
> 
> Can you please send the exact steps you are using to configure and 
> compile QEMU,
> are you compiling on a x86 machine?

Yes, this is on my laptop (up-to-date F28). I can reproduce on current
master, configured with

../configure --target-list="s390x-softmmu s390x-linux-user i386-softmmu x86_64-softmmu cris-softmmu arm-softmmu ppc64-softmmu" --enable-linux-aio --enable-virtfs --enable-trace-backends=simple --cc=clang --enable-rdma --enable-pvrdma

It compiles if I pass --disable-pvrdma instead. It also compiles if I
drop --cc=clang.

I'm building in a build subdirectory; I have already tried purging it
before rebuilding, without luck.

clang --version says

clang version 6.0.1 (tags/RELEASE_601/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin