Commit 5105b1d8 authored by David Marchand's avatar David Marchand Committed by Marc-André Lureau
Browse files

ivshmem: add check on protocol version in QEMU 



Send a protocol version as the first message from server, clients must
close communication if they don't support this protocol version.  Older
QEMUs should be fine with this change in the protocol since they
overrides their own vm_id on reception of an id associated to no
eventfd.

Signed-off-by: default avatarDavid Marchand <david.marchand@6wind.com>
Signed-off-by: default avatarMarc-André Lureau <marcandre.lureau@redhat.com>
[use fifo_update_and_get()]
Reviewed-by: default avatarClaudio Fontana <claudio.fontana@huawei.com>
parent 8c4ef202

contrib/ivshmem-client/ivshmem-client.c

+10 −3
Original line number Diff line number Diff line
@@ -206,10 +206,17 @@ ivshmem_client_connect(IvshmemClient *client) 
        goto err_close;

    }



    /* first, we expect our index + a fd == -1 */

    /* first, we expect a protocol version */

    if (ivshmem_client_read_one_msg(client, &tmp, &fd) < 0 ||

        (tmp != IVSHMEM_PROTOCOL_VERSION) || fd != -1) {

        IVSHMEM_CLIENT_DEBUG(client, "cannot read from server\n");

        goto err_close;

    }



    /* then, we expect our index + a fd == -1 */

    if (ivshmem_client_read_one_msg(client, &client->local.id, &fd) < 0 ||

        client->local.id < 0 || fd != -1) {

        IVSHMEM_CLIENT_DEBUG(client, "cannot read from server\n");

        IVSHMEM_CLIENT_DEBUG(client, "cannot read from server (2)\n");

        goto err_close;

    }

    IVSHMEM_CLIENT_DEBUG(client, "our_id=%ld\n", client->local.id);
@@ -221,7 +228,7 @@ ivshmem_client_connect(IvshmemClient *client) 
        if (fd >= 0) {

            close(fd);

        }

        IVSHMEM_CLIENT_DEBUG(client, "cannot read from server (2)\n");

        IVSHMEM_CLIENT_DEBUG(client, "cannot read from server (3)\n");

        goto err_close;

    }

    client->shm_fd = fd;

contrib/ivshmem-client/ivshmem-client.h

+1 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <sys/select.h>



#include "qemu/queue.h"

#include "hw/misc/ivshmem.h"



/**

 * Maximum number of notification vectors supported by the client

contrib/ivshmem-server/ivshmem-server.c

+9 −0
Original line number Diff line number Diff line
@@ -101,6 +101,15 @@ ivshmem_server_send_initial_info(IvshmemServer *server, IvshmemServerPeer *peer) 
{

    int ret;



    /* send our protocol version first */

    ret = ivshmem_server_send_one_msg(peer->sock_fd, IVSHMEM_PROTOCOL_VERSION,

                                      -1);

    if (ret < 0) {

        IVSHMEM_SERVER_DEBUG(server, "cannot send version: %s\n",

                             strerror(errno));

        return -1;

    }



    /* send the peer id to the client */

    ret = ivshmem_server_send_one_msg(peer->sock_fd, peer->id, -1);

    if (ret < 0) {

contrib/ivshmem-server/ivshmem-server.h

+1 −0
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ 


#include "qemu/event_notifier.h"

#include "qemu/queue.h"

#include "hw/misc/ivshmem.h"



/**

 * Maximum number of notification vectors supported by the server

docs/specs/ivshmem_device_spec.txt

+6 −3
Original line number Diff line number Diff line
@@ -64,6 +64,8 @@ It creates a shared memory object then waits for clients to connect on a unix 
socket.



For each client (QEMU process) that connects to the server:

- the server sends a protocol version, if client does not support it, the client

  closes the communication,

- the server assigns an ID for this client and sends this ID to him as the first

  message,

- the server sends a fd to the shared memory object to this client,
@@ -86,9 +88,10 @@ been provided in qemu.git/contrib/ivshmem-client for debug. 


*QEMU as an ivshmem client*



At initialisation, when creating the ivshmem device, QEMU gets its ID from the

server then makes it available through BAR0 IVPosition register for the VM to

use (see 'PCI device registers' subsection).

At initialisation, when creating the ivshmem device, QEMU first receives a

protocol version and closes communication with server if it does not match.

Then, QEMU gets its ID from the server then makes it available through BAR0

IVPosition register for the VM to use (see 'PCI device registers' subsection).

QEMU then uses the fd to the shared memory to map it to BAR2.

eventfds for all other clients received from the server are stored to implement

BAR0 Doorbell register (see 'PCI device registers' subsection).