Re: [PATCH v2 18/19] xen/sndfront: use xenbus_setup_ring() and xenbus_teardown_ring()

[Oleksandr <olekstysh@xxxxxxxxx>]

On 28.04.22 11:27, Juergen Gross wrote:

Hello Juergen, all

> Simplify sndfront's ring creation and removal via xenbus_setup_ring()
> and xenbus_teardown_ring().
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
I am not familiar with SOUND bits of this driver, but a little bit
familiar with Xen bits this patch only touches and I have environment to
test.

Xen specific changes looks good to me. Also I didn't see any issues when 
testing virtulized sound driver with current series except one I have 
already pointed out in PATCH v2 08/19.

root@salvator-x-h3-4x2g-xt-domu:~# dmesg | grep vsnd
[    0.432181] Initialising Xen vsnd frontend driver


root@salvator-x-h3-4x2g-xt-domu:~# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: vsnd [], device 0: dev1 [Virtual card PCM]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

root@generic-armv8-xt-dom0:~# xenstore-ls -f | grep vsnd
/local/domain/1/backend/vsnd = ""
/local/domain/1/backend/vsnd/6 = ""
/local/domain/1/backend/vsnd/6/0 = ""
/local/domain/1/backend/vsnd/6/0/frontend = "/local/domain/6/device/vsnd/0"
/local/domain/1/backend/vsnd/6/0/frontend-id = "6"
/local/domain/1/backend/vsnd/6/0/online = "1"
/local/domain/1/backend/vsnd/6/0/state = "4"
/local/domain/6/device/vsnd = ""
/local/domain/6/device/vsnd/0 = ""
/local/domain/6/device/vsnd/0/backend = "/local/domain/1/backend/vsnd/6/0"
/local/domain/6/device/vsnd/0/backend-id = "1"
/local/domain/6/device/vsnd/0/state = "4"
/local/domain/6/device/vsnd/0/long-name = "Virtual sound card"
/local/domain/6/device/vsnd/0/short-name = "VCard"
/local/domain/6/device/vsnd/0/sample-rates = 
"8000,11025,16000,22050,32000,44100,48000"
/local/domain/6/device/vsnd/0/sample-formats = "s16_le"
/local/domain/6/device/vsnd/0/buffer-size = "65536"
/local/domain/6/device/vsnd/0/0 = ""
/local/domain/6/device/vsnd/0/0/name = "dev1"
/local/domain/6/device/vsnd/0/0/0 = ""
/local/domain/6/device/vsnd/0/0/0/unique-id = "pulse"
/local/domain/6/device/vsnd/0/0/0/type = "p"
/local/domain/6/device/vsnd/0/0/0/ring-ref = "2070"
/local/domain/6/device/vsnd/0/0/0/event-channel = "18"
/local/domain/6/device/vsnd/0/0/0/evt-ring-ref = "2071"
/local/domain/6/device/vsnd/0/0/0/evt-event-channel = "19"
/libxl/6/device/vsnd = ""
/libxl/6/device/vsnd/0 = ""
/libxl/6/device/vsnd/0/frontend = "/local/domain/6/device/vsnd/0"
/libxl/6/device/vsnd/0/backend = "/local/domain/1/backend/vsnd/6/0"
/libxl/6/device/vsnd/0/frontend-id = "6"
/libxl/6/device/vsnd/0/online = "1"
/libxl/6/device/vsnd/0/state = "1"


> ---
>   sound/xen/xen_snd_front_evtchnl.c | 44 +++++++------------------------
>   1 file changed, 10 insertions(+), 34 deletions(-)
>
> diff --git a/sound/xen/xen_snd_front_evtchnl.c 
> b/sound/xen/xen_snd_front_evtchnl.c
> index 3e21369c8216..26d1b3987887 100644
> --- a/sound/xen/xen_snd_front_evtchnl.c
> +++ b/sound/xen/xen_snd_front_evtchnl.c
> @@ -143,12 +143,12 @@ void xen_snd_front_evtchnl_flush(struct 
> xen_snd_front_evtchnl *channel)
>   static void evtchnl_free(struct xen_snd_front_info *front_info,
>                          struct xen_snd_front_evtchnl *channel)
>   {
> -       unsigned long page = 0;
> +       void *page = NULL;
>   
>   	if (channel->type == EVTCHNL_TYPE_REQ)
> -               page = (unsigned long)channel->u.req.ring.sring;
> +               page = channel->u.req.ring.sring;
>         else if (channel->type == EVTCHNL_TYPE_EVT)
> -               page = (unsigned long)channel->u.evt.page;
> +               page = channel->u.evt.page;
>   
>   	if (!page)
>                 return;
> @@ -167,10 +167,7 @@ static void evtchnl_free(struct xen_snd_front_info 
> *front_info,
>                 xenbus_free_evtchn(front_info->xb_dev, channel->port);
>   
>   	/* End access and free the page. */
> -       if (channel->gref != INVALID_GRANT_REF)
> -               gnttab_end_foreign_access(channel->gref, page);
> -       else
> -               free_page(page);
> +       xenbus_teardown_ring(&page, 1, &channel->gref);
>   
>   	memset(channel, 0, sizeof(*channel));
>   }
> @@ -196,8 +193,7 @@ static int evtchnl_alloc(struct xen_snd_front_info 
> *front_info, int index,
>                          enum xen_snd_front_evtchnl_type type)
>   {
>         struct xenbus_device *xb_dev = front_info->xb_dev;
> -       unsigned long page;
> -       grant_ref_t gref;
> +       void *page;
>         irq_handler_t handler;
>         char *handler_name = NULL;
>         int ret;
> @@ -207,12 +203,9 @@ static int evtchnl_alloc(struct xen_snd_front_info 
> *front_info, int index,
>         channel->index = index;
>         channel->front_info = front_info;
>         channel->state = EVTCHNL_STATE_DISCONNECTED;
> -       channel->gref = INVALID_GRANT_REF;
> -       page = get_zeroed_page(GFP_KERNEL);
> -       if (!page) {
> -               ret = -ENOMEM;
> +       ret = xenbus_setup_ring(xb_dev, GFP_KERNEL, &page, 1, &channel->gref);
> +       if (ret)
>                 goto fail;
> -       }
>   
>   	handler_name = kasprintf(GFP_KERNEL, "%s-%s", XENSND_DRIVER_NAME,
>                                  type == EVTCHNL_TYPE_REQ ?
> @@ -226,33 +219,18 @@ static int evtchnl_alloc(struct xen_snd_front_info 
> *front_info, int index,
>         mutex_init(&channel->ring_io_lock);
>   
>   	if (type == EVTCHNL_TYPE_REQ) {
> -               struct xen_sndif_sring *sring = (struct xen_sndif_sring *)page;
> +               struct xen_sndif_sring *sring = page;
>   
>   		init_completion(&channel->u.req.completion);
>                 mutex_init(&channel->u.req.req_io_lock);
> -               SHARED_RING_INIT(sring);
> -               FRONT_RING_INIT(&channel->u.req.ring, sring, XEN_PAGE_SIZE);
> -
> -               ret = xenbus_grant_ring(xb_dev, sring, 1, &gref);
> -               if (ret < 0) {
> -                       channel->u.req.ring.sring = NULL;
> -                       goto fail;
> -               }
> +               XEN_FRONT_RING_INIT(&channel->u.req.ring, sring, XEN_PAGE_SIZE);
>   
>   		handler = evtchnl_interrupt_req;
>         } else {
> -               ret = gnttab_grant_foreign_access(xb_dev->otherend_id,
> -                                                 virt_to_gfn((void *)page), 0);
> -               if (ret < 0)
> -                       goto fail;
> -
> -               channel->u.evt.page = (struct xensnd_event_page *)page;
> -               gref = ret;
> +               channel->u.evt.page = page;
>                 handler = evtchnl_interrupt_evt;
>         }
>   
> -	channel->gref = gref;
> -
>         ret = xenbus_alloc_evtchn(xb_dev, &channel->port);
>         if (ret < 0)
>                 goto fail;
> @@ -279,8 +257,6 @@ static int evtchnl_alloc(struct xen_snd_front_info 
> *front_info, int index,
>         return 0;
>   
>   fail:
> -       if (page)
> -               free_page(page);
>         kfree(handler_name);
>         dev_err(&xb_dev->dev, "Failed to allocate ring: %d\n", ret);
>         return ret;
--
Regards,

Oleksandr Tyshchenko