Re: [PATCH v5 12/18] vfio-user: run vfio-user context

[Stefan Hajnoczi]

On Wed, Jan 19, 2022 at 04:42:01PM -0500, Jagannathan Raman wrote:
> Setup a handler to run vfio-user context. The context is driven by
> messages to the file descriptor associated with it - get the fd for
> the context and hook up the handler with it
> 
> Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
> Signed-off-by: John G Johnson <john.g.johnson@oracle.com>
> Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
> ---
>  qapi/misc.json            | 23 ++++++++++
>  hw/remote/vfio-user-obj.c | 90 ++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 112 insertions(+), 1 deletion(-)
> 
> diff --git a/qapi/misc.json b/qapi/misc.json
> index e8054f415b..f0791d3311 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -527,3 +527,26 @@
>   'data': { '*option': 'str' },
>   'returns': ['CommandLineOptionInfo'],
>   'allow-preconfig': true }
> +
> +##
> +# @VFU_CLIENT_HANGUP:
> +#
> +# Emitted when the client of a TYPE_VFIO_USER_SERVER closes the
> +# communication channel
> +#
> +# @device: ID of attached PCI device
> +#
> +# @path: path of the socket

This assumes a UNIX domain socket path was given. It doesn't work well
with file descriptor passing. The x-vfio-user-server is an object with
a unique QEMU Object Model path (the last path component is its id). You
can get the id like this:

  object_get_canonical_path_component(OBJECT(o))

I suggest dropping @path and including the server object's id instead.

> +#
> +# Since: 6.3
> +#
> +# Example:
> +#
> +# <- { "event": "VFU_CLIENT_HANGUP",
> +#      "data": { "device": "lsi1",
> +#                "path": "/tmp/vfu1-sock" },
> +#      "timestamp": { "seconds": 1265044230, "microseconds": 450486 } }
> +#
> +##
> +{ 'event': 'VFU_CLIENT_HANGUP',
> +  'data': { 'device': 'str', 'path': 'str' } }
> diff --git a/hw/remote/vfio-user-obj.c b/hw/remote/vfio-user-obj.c
> index 10db78eb8d..91d49a221f 100644
> --- a/hw/remote/vfio-user-obj.c
> +++ b/hw/remote/vfio-user-obj.c
> @@ -27,6 +27,9 @@
>   *
>   * device - id of a device on the server, a required option. PCI devices
>   *          alone are supported presently.
> + *
> + * notes - x-vfio-user-server could block IO and monitor during the
> + *         initialization phase.
>   */
>  
>  #include "qemu/osdep.h"
> @@ -41,11 +44,14 @@
>  #include "hw/remote/machine.h"
>  #include "qapi/error.h"
>  #include "qapi/qapi-visit-sockets.h"
> +#include "qapi/qapi-events-misc.h"
>  #include "qemu/notify.h"
> +#include "qemu/thread.h"
>  #include "sysemu/sysemu.h"
>  #include "libvfio-user.h"
>  #include "hw/qdev-core.h"
>  #include "hw/pci/pci.h"
> +#include "qemu/timer.h"
>  
>  #define TYPE_VFU_OBJECT "x-vfio-user-server"
>  OBJECT_DECLARE_TYPE(VfuObject, VfuObjectClass, VFU_OBJECT)
> @@ -95,6 +101,8 @@ struct VfuObject {
>      PCIDevice *pci_dev;
>  
>      Error *unplug_blocker;
> +
> +    int vfu_poll_fd;
>  };
>  
>  static void vfu_object_init_ctx(VfuObject *o, Error **errp);
> @@ -144,6 +152,68 @@ static void vfu_object_set_device(Object *obj, const 
> char *str, Error **errp)
>      vfu_object_init_ctx(o, errp);
>  }
>  
> +static void vfu_object_ctx_run(void *opaque)
> +{
> +    VfuObject *o = opaque;
> +    int ret = -1;
> +
> +    while (ret != 0) {
> +        ret = vfu_run_ctx(o->vfu_ctx);
> +        if (ret < 0) {
> +            if (errno == EINTR) {
> +                continue;
> +            } else if (errno == ENOTCONN) {
> +                qapi_event_send_vfu_client_hangup(o->device,
> +                                                  o->socket->u.q_unix.path);
> +                qemu_set_fd_handler(o->vfu_poll_fd, NULL, NULL, NULL);

Do we also stop monitoring o->vfu_poll_fd when object-del is used to
delete the x-vfio-user-server object?

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