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SubjectRe: [PATCH v2 3/5] ALSA: xen-front: Implement Xen event channel handling
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On 16/04/18 08:24, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>
> Handle Xen event channels:
> - create for all configured streams and publish
> corresponding ring references and event channels in Xen store,
> so backend can connect
> - implement event channels interrupt handlers
> - create and destroy event channels with respect to Xen bus state
>
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> ---
> sound/xen/Makefile | 3 +-
> sound/xen/xen_snd_front.c | 10 +-
> sound/xen/xen_snd_front.h | 7 +
> sound/xen/xen_snd_front_evtchnl.c | 474 ++++++++++++++++++++++++++++++++++++++
> sound/xen/xen_snd_front_evtchnl.h | 92 ++++++++
> 5 files changed, 584 insertions(+), 2 deletions(-)
> create mode 100644 sound/xen/xen_snd_front_evtchnl.c
> create mode 100644 sound/xen/xen_snd_front_evtchnl.h
>
> diff --git a/sound/xen/Makefile b/sound/xen/Makefile
> index 06705bef61fa..03c669984000 100644
> --- a/sound/xen/Makefile
> +++ b/sound/xen/Makefile
> @@ -1,6 +1,7 @@
> # SPDX-License-Identifier: GPL-2.0 OR MIT
>
> snd_xen_front-objs := xen_snd_front.o \
> - xen_snd_front_cfg.o
> + xen_snd_front_cfg.o \
> + xen_snd_front_evtchnl.o
>
> obj-$(CONFIG_SND_XEN_FRONTEND) += snd_xen_front.o
> diff --git a/sound/xen/xen_snd_front.c b/sound/xen/xen_snd_front.c
> index 65d2494a9d14..eb46bf4070f9 100644
> --- a/sound/xen/xen_snd_front.c
> +++ b/sound/xen/xen_snd_front.c
> @@ -18,9 +18,11 @@
> #include <xen/interface/io/sndif.h>
>
> #include "xen_snd_front.h"
> +#include "xen_snd_front_evtchnl.h"

Does it really make sense to have multiple driver-private headers?

I think those can be merged.

>
> static void xen_snd_drv_fini(struct xen_snd_front_info *front_info)
> {
> + xen_snd_front_evtchnl_free_all(front_info);
> }
>
> static int sndback_initwait(struct xen_snd_front_info *front_info)
> @@ -32,7 +34,12 @@ static int sndback_initwait(struct xen_snd_front_info *front_info)
> if (ret < 0)
> return ret;
>
> - return 0;
> + /* create event channels for all streams and publish */
> + ret = xen_snd_front_evtchnl_create_all(front_info, num_streams);
> + if (ret < 0)
> + return ret;
> +
> + return xen_snd_front_evtchnl_publish_all(front_info);
> }
>
> static int sndback_connect(struct xen_snd_front_info *front_info)
> @@ -122,6 +129,7 @@ static int xen_drv_probe(struct xenbus_device *xb_dev,
> return -ENOMEM;
>
> front_info->xb_dev = xb_dev;
> + spin_lock_init(&front_info->io_lock);
> dev_set_drvdata(&xb_dev->dev, front_info);
>
> return xenbus_switch_state(xb_dev, XenbusStateInitialising);
> diff --git a/sound/xen/xen_snd_front.h b/sound/xen/xen_snd_front.h
> index b52226cb30bc..9c2ffbb4e4b8 100644
> --- a/sound/xen/xen_snd_front.h
> +++ b/sound/xen/xen_snd_front.h
> @@ -13,9 +13,16 @@
>
> #include "xen_snd_front_cfg.h"
>
> +struct xen_snd_front_evtchnl_pair;
> +
> struct xen_snd_front_info {
> struct xenbus_device *xb_dev;
>
> + /* serializer for backend IO: request/response */
> + spinlock_t io_lock;
> + int num_evt_pairs;
> + struct xen_snd_front_evtchnl_pair *evt_pairs;
> +
> struct xen_front_cfg_card cfg;
> };
>
> diff --git a/sound/xen/xen_snd_front_evtchnl.c b/sound/xen/xen_snd_front_evtchnl.c
> new file mode 100644
> index 000000000000..9ece39f938f8
> --- /dev/null
> +++ b/sound/xen/xen_snd_front_evtchnl.c
> @@ -0,0 +1,474 @@
> +// SPDX-License-Identifier: GPL-2.0 OR MIT
> +
> +/*
> + * Xen para-virtual sound device
> + *
> + * Copyright (C) 2016-2018 EPAM Systems Inc.
> + *
> + * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> + */
> +
> +#include <xen/events.h>
> +#include <xen/grant_table.h>
> +#include <xen/xen.h>
> +#include <xen/xenbus.h>
> +
> +#include "xen_snd_front.h"
> +#include "xen_snd_front_cfg.h"
> +#include "xen_snd_front_evtchnl.h"
> +
> +static irqreturn_t evtchnl_interrupt_req(int irq, void *dev_id)
> +{
> + struct xen_snd_front_evtchnl *channel = dev_id;
> + struct xen_snd_front_info *front_info = channel->front_info;
> + struct xensnd_resp *resp;
> + RING_IDX i, rp;
> + unsigned long flags;
> +
> + if (unlikely(channel->state != EVTCHNL_STATE_CONNECTED))
> + return IRQ_HANDLED;
> +
> + spin_lock_irqsave(&front_info->io_lock, flags);
> +
> +again:
> + rp = channel->u.req.ring.sring->rsp_prod;
> + /* ensure we see queued responses up to rp */
> + rmb();
> +
> + for (i = channel->u.req.ring.rsp_cons; i != rp; i++) {
> + resp = RING_GET_RESPONSE(&channel->u.req.ring, i);
> + if (resp->id != channel->evt_id)
> + continue;
> + switch (resp->operation) {
> + case XENSND_OP_OPEN:
> + /* fall through */
> + case XENSND_OP_CLOSE:
> + /* fall through */
> + case XENSND_OP_READ:
> + /* fall through */
> + case XENSND_OP_WRITE:
> + /* fall through */
> + case XENSND_OP_TRIGGER:
> + channel->u.req.resp_status = resp->status;
> + complete(&channel->u.req.completion);
> + break;
> + case XENSND_OP_HW_PARAM_QUERY:
> + channel->u.req.resp_status = resp->status;
> + channel->u.req.resp.hw_param =
> + resp->resp.hw_param;
> + complete(&channel->u.req.completion);
> + break;
> +
> + default:
> + dev_err(&front_info->xb_dev->dev,
> + "Operation %d is not supported\n",
> + resp->operation);
> + break;
> + }
> + }
> +
> + channel->u.req.ring.rsp_cons = i;
> + if (i != channel->u.req.ring.req_prod_pvt) {
> + int more_to_do;
> +
> + RING_FINAL_CHECK_FOR_RESPONSES(&channel->u.req.ring,
> + more_to_do);
> + if (more_to_do)
> + goto again;
> + } else {
> + channel->u.req.ring.sring->rsp_event = i + 1;
> + }
> +
> + spin_unlock_irqrestore(&front_info->io_lock, flags);
> + return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t evtchnl_interrupt_evt(int irq, void *dev_id)
> +{
> + struct xen_snd_front_evtchnl *channel = dev_id;
> + struct xen_snd_front_info *front_info = channel->front_info;
> + struct xensnd_event_page *page = channel->u.evt.page;
> + u32 cons, prod;
> + unsigned long flags;
> +
> + if (unlikely(channel->state != EVTCHNL_STATE_CONNECTED))
> + return IRQ_HANDLED;
> +
> + spin_lock_irqsave(&front_info->io_lock, flags);
> +
> + prod = page->in_prod;
> + /* ensure we see ring contents up to prod */
> + virt_rmb();
> + if (prod == page->in_cons)
> + goto out;
> +
> + for (cons = page->in_cons; cons != prod; cons++) {
> + struct xensnd_evt *event;
> +
> + event = &XENSND_IN_RING_REF(page, cons);
> + if (unlikely(event->id != channel->evt_id++))
> + continue;
> +
> + switch (event->type) {
> + case XENSND_EVT_CUR_POS:
> + /* do nothing at the moment */
> + break;
> + }
> + }
> +
> + page->in_cons = cons;
> + /* ensure ring contents */
> + virt_wmb();
> +
> +out:
> + spin_unlock_irqrestore(&front_info->io_lock, flags);
> + return IRQ_HANDLED;
> +}
> +
> +void xen_snd_front_evtchnl_flush(struct xen_snd_front_evtchnl *channel)
> +{
> + int notify;
> +
> + channel->u.req.ring.req_prod_pvt++;
> + RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&channel->u.req.ring, notify);
> + if (notify)
> + notify_remote_via_irq(channel->irq);
> +}
> +
> +static void evtchnl_free(struct xen_snd_front_info *front_info,
> + struct xen_snd_front_evtchnl *channel)
> +{
> + unsigned long page = 0;
> +
> + if (channel->type == EVTCHNL_TYPE_REQ)
> + page = (unsigned long)channel->u.req.ring.sring;
> + else if (channel->type == EVTCHNL_TYPE_EVT)
> + page = (unsigned long)channel->u.evt.page;
> +
> + if (!page)
> + return;
> +
> + channel->state = EVTCHNL_STATE_DISCONNECTED;
> + if (channel->type == EVTCHNL_TYPE_REQ) {
> + /* release all who still waits for response if any */
> + channel->u.req.resp_status = -EIO;
> + complete_all(&channel->u.req.completion);
> + }
> +
> + if (channel->irq)
> + unbind_from_irqhandler(channel->irq, channel);
> +
> + if (channel->port)
> + xenbus_free_evtchn(front_info->xb_dev, channel->port);
> +
> + /* end access and free the page */
> + if (channel->gref != GRANT_INVALID_REF)
> + gnttab_end_foreign_access(channel->gref, 0, page);

Free page?

> +
> + memset(channel, 0, sizeof(*channel));
> +}
> +
> +void xen_snd_front_evtchnl_free_all(struct xen_snd_front_info *front_info)
> +{
> + int i;
> +
> + if (!front_info->evt_pairs)
> + return;
> +
> + for (i = 0; i < front_info->num_evt_pairs; i++) {
> + evtchnl_free(front_info, &front_info->evt_pairs[i].req);
> + evtchnl_free(front_info, &front_info->evt_pairs[i].evt);
> + }
> +
> + kfree(front_info->evt_pairs);
> + front_info->evt_pairs = NULL;
> +}
> +
> +static int evtchnl_alloc(struct xen_snd_front_info *front_info, int index,
> + struct xen_snd_front_evtchnl *channel,
> + enum xen_snd_front_evtchnl_type type)
> +{
> + struct xenbus_device *xb_dev = front_info->xb_dev;
> + unsigned long page;
> + grant_ref_t gref;
> + irq_handler_t handler;
> + char *handler_name = NULL;
> + int ret;
> +
> + memset(channel, 0, sizeof(*channel));
> + channel->type = type;
> + channel->index = index;
> + channel->front_info = front_info;
> + channel->state = EVTCHNL_STATE_DISCONNECTED;
> + channel->gref = GRANT_INVALID_REF;
> + page = get_zeroed_page(GFP_NOIO | __GFP_HIGH);

Why GFP_NOIO | __GFP_HIGH? Could it be you copied that from blkfront
driver? I believe swapping via sound card is rather uncommon.

> + if (!page) {
> + ret = -ENOMEM;
> + goto fail;
> + }
> +
> + handler_name = kasprintf(GFP_KERNEL, "%s-%s", XENSND_DRIVER_NAME,
> + type == EVTCHNL_TYPE_REQ ?
> + XENSND_FIELD_RING_REF :
> + XENSND_FIELD_EVT_RING_REF);
> + if (!handler_name) {
> + ret = -ENOMEM;

Missing free_page(page)? Maybe you rather add it in the common
fail path instead of the numerous instances below?


Juergen

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