Re: [Qemu-devel] [RFC v2 06/12] vhost-user: add vhost_user_input_get_config()

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Marc-André Lureau (marcandre.lureau@redhat.com) wrote:
> Hi
> 
> On Mon, Jun 4, 2018 at 11:07 AM, Dr. David Alan Gilbert
> <dgilbert@redhat.com> wrote:
> > * Marc-André Lureau (marcandre.lureau@redhat.com) wrote:
> >> Ask vhost user input backend the list of virtio_input_config.
> >
> > Why is this vhost-user specific; shouldn't the vhost-input
> > behaviour be the same irrespective of if it's vhost-user or plain vhost?
> >
> 
> A similar message could be used for plain vhost, in some ioctl form.
> Here we are documenting vhost-user protocol only.

The vhost-user protocol seems to be mostly independent of the device
it's carrying; for example I see there's a 'net_set_mtu' and 'send_rarp'
but I don't think there's anything for disk storage;  what are the cases
whether these have to be done through a change to the vhost-user
protocol as opposed to stuff carried over it?

Dave

> 
> Thanks
> 
> > Dave
> >
> >
> >> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> >> ---
> >>  include/hw/virtio/vhost-backend.h |  4 +++
> >>  hw/virtio/vhost-user.c            | 59 +++++++++++++++++++++++++++++++
> >>  docs/interop/vhost-user.txt       |  6 ++++
> >>  3 files changed, 69 insertions(+)
> >>
> >> diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
> >> index 5dac61f9ea..6cc2edacc5 100644
> >> --- a/include/hw/virtio/vhost-backend.h
> >> +++ b/include/hw/virtio/vhost-backend.h
> >> @@ -12,6 +12,7 @@
> >>  #define VHOST_BACKEND_H
> >>
> >>  #include "exec/memory.h"
> >> +#include "standard-headers/linux/virtio_input.h"
> >>
> >>  typedef enum VhostBackendType {
> >>      VHOST_BACKEND_TYPE_NONE = 0,
> >> @@ -156,4 +157,7 @@ int vhost_backend_invalidate_device_iotlb(struct vhost_dev *dev,
> >>  int vhost_backend_handle_iotlb_msg(struct vhost_dev *dev,
> >>                                            struct vhost_iotlb_msg *imsg);
> >>
> >> +int vhost_user_input_get_config(struct vhost_dev *dev,
> >> +                                struct virtio_input_config **config);
> >> +
> >>  #endif /* VHOST_BACKEND_H */
> >> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> >> index a87db01e55..19ed87d07c 100644
> >> --- a/hw/virtio/vhost-user.c
> >> +++ b/hw/virtio/vhost-user.c
> >> @@ -84,6 +84,7 @@ typedef enum VhostUserRequest {
> >>      VHOST_USER_POSTCOPY_ADVISE  = 28,
> >>      VHOST_USER_POSTCOPY_LISTEN  = 29,
> >>      VHOST_USER_POSTCOPY_END     = 30,
> >> +    VHOST_USER_INPUT_GET_CONFIG,
> >>      VHOST_USER_MAX
> >>  } VhostUserRequest;
> >>
> >> @@ -324,6 +325,64 @@ static int vhost_user_write(struct vhost_dev *dev, VhostUserMsg *msg,
> >>      return 0;
> >>  }
> >>
> >> +static void *vhost_user_read_size(struct vhost_dev *dev, uint32_t size)
> >> +{
> >> +    struct vhost_user *u = dev->opaque;
> >> +    CharBackend *chr = u->chr;
> >> +    int r;
> >> +    uint8_t *p = g_malloc(size);
> >> +
> >> +    r = qemu_chr_fe_read_all(chr, p, size);
> >> +    if (r != size) {
> >> +        error_report("Failed to read msg payload."
> >> +                     " Read %d instead of %d.", r, size);
> >> +        return NULL;
> >> +    }
> >> +
> >> +    return p;
> >> +}
> >> +
> >> +int vhost_user_input_get_config(struct vhost_dev *dev,
> >> +                                struct virtio_input_config **config)
> >> +{
> >> +    void *p = NULL;
> >> +    VhostUserMsg msg = {
> >> +        .hdr.request = VHOST_USER_INPUT_GET_CONFIG,
> >> +        .hdr.flags = VHOST_USER_VERSION,
> >> +    };
> >> +
> >> +    if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
> >> +        goto err;
> >> +    }
> >> +
> >> +    if (vhost_user_read_header(dev, &msg) < 0) {
> >> +        goto err;
> >> +    }
> >> +
> >> +    p = vhost_user_read_size(dev, msg.hdr.size);
> >> +    if (!p) {
> >> +        goto err;
> >> +    }
> >> +
> >> +    if (msg.hdr.request != VHOST_USER_INPUT_GET_CONFIG) {
> >> +        error_report("Received unexpected msg type. Expected %d received %d",
> >> +                     VHOST_USER_INPUT_GET_CONFIG, msg.hdr.request);
> >> +        goto err;
> >> +    }
> >> +
> >> +    if (msg.hdr.size % sizeof(struct virtio_input_config)) {
> >> +        error_report("Invalid msg size");
> >> +        goto err;
> >> +    }
> >> +
> >> +    *config = p;
> >> +    return msg.hdr.size / sizeof(struct virtio_input_config);
> >> +
> >> +err:
> >> +    g_free(p);
> >> +    return -1;
> >> +}
> >> +
> >>  static int vhost_user_set_log_base(struct vhost_dev *dev, uint64_t base,
> >>                                     struct vhost_log *log)
> >>  {
> >> diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
> >> index 534caab18a..3df9927386 100644
> >> --- a/docs/interop/vhost-user.txt
> >> +++ b/docs/interop/vhost-user.txt
> >> @@ -744,6 +744,12 @@ Master message types
> >>        was previously sent.
> >>        The value returned is an error indication; 0 is success.
> >>
> >> + * VHOST_USER_INPUT_GET_CONFIG
> >> +
> >> +      Slave payload: (struct virtio_input_config)*
> >> +
> >> +      Ask vhost user input backend the list of virtio_input_config.
> >> +
> >>  Slave message types
> >>  -------------------
> >>
> >> --
> >> 2.17.1.906.g10fd178552
> >>
> >>
> > --
> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK