[PATCH v2 3/5] ALSA: xen-front: Implement Xen event channel handling

From: Oleksandr Andrushchenko
Date: Mon Apr 16 2018 - 02:25:21 EST

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

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@xxxxxxxx>
---
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"

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@xxxxxxxx>
+ */
+
+#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);
+
+ 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);
+ 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;
+ goto fail;
+ }
+
+ if (type == EVTCHNL_TYPE_REQ) {
+ struct xen_sndif_sring *sring = (struct xen_sndif_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;
+ free_page(page);
+ goto fail;
+ }
+
+ handler = evtchnl_interrupt_req;
+ } else {
+ ret = gnttab_grant_foreign_access(xb_dev->otherend_id,
+ virt_to_gfn((void *)page), 0);
+ if (ret < 0) {
+ free_page(page);
+ goto fail;
+ }
+
+ channel->u.evt.page = (struct xensnd_event_page *)page;
+ gref = ret;
+ handler = evtchnl_interrupt_evt;
+ }
+
+ channel->gref = gref;
+
+ ret = xenbus_alloc_evtchn(xb_dev, &channel->port);
+ if (ret < 0)
+ goto fail;
+
+ ret = bind_evtchn_to_irq(channel->port);
+ if (ret < 0) {
+ dev_err(&xb_dev->dev,
+ "Failed to bind IRQ for domid %d port %d: %d\n",
+ front_info->xb_dev->otherend_id, channel->port, ret);
+ goto fail;
+ }
+
+ channel->irq = ret;
+
+ ret = request_threaded_irq(channel->irq, NULL, handler,
+ IRQF_ONESHOT, handler_name, channel);
+ if (ret < 0) {
+ dev_err(&xb_dev->dev, "Failed to request IRQ %d: %d\n",
+ channel->irq, ret);
+ goto fail;
+ }
+
+ kfree(handler_name);
+ return 0;
+
+fail:
+ kfree(handler_name);
+ dev_err(&xb_dev->dev, "Failed to allocate ring: %d\n", ret);
+ return ret;
+}
+
+int xen_snd_front_evtchnl_create_all(struct xen_snd_front_info *front_info,
+ int num_streams)
+{
+ struct xen_front_cfg_card *cfg = &front_info->cfg;
+ struct device *dev = &front_info->xb_dev->dev;
+ int d, ret = 0;
+
+ front_info->evt_pairs =
+ kcalloc(num_streams,
+ sizeof(struct xen_snd_front_evtchnl_pair),
+ GFP_KERNEL);
+ if (!front_info->evt_pairs)
+ return -ENOMEM;
+
+ /* iterate over devices and their streams and create event channels */
+ for (d = 0; d < cfg->num_pcm_instances; d++) {
+ struct xen_front_cfg_pcm_instance *pcm_instance;
+ int s, index;
+
+ pcm_instance = &cfg->pcm_instances[d];
+
+ for (s = 0; s < pcm_instance->num_streams_pb; s++) {
+ index = pcm_instance->streams_pb[s].index;
+
+ ret = evtchnl_alloc(front_info, index,
+ &front_info->evt_pairs[index].req,
+ EVTCHNL_TYPE_REQ);
+ if (ret < 0) {
+ dev_err(dev, "Error allocating control channel\n");
+ goto fail;
+ }
+
+ ret = evtchnl_alloc(front_info, index,
+ &front_info->evt_pairs[index].evt,
+ EVTCHNL_TYPE_EVT);
+ if (ret < 0) {
+ dev_err(dev, "Error allocating in-event channel\n");
+ goto fail;
+ }
+ }
+
+ for (s = 0; s < pcm_instance->num_streams_cap; s++) {
+ index = pcm_instance->streams_cap[s].index;
+
+ ret = evtchnl_alloc(front_info, index,
+ &front_info->evt_pairs[index].req,
+ EVTCHNL_TYPE_REQ);
+ if (ret < 0) {
+ dev_err(dev, "Error allocating control channel\n");
+ goto fail;
+ }
+
+ ret = evtchnl_alloc(front_info, index,
+ &front_info->evt_pairs[index].evt,
+ EVTCHNL_TYPE_EVT);
+ if (ret < 0) {
+ dev_err(dev, "Error allocating in-event channel\n");
+ goto fail;
+ }
+ }
+ }
+ if (ret < 0)
+ goto fail;
+
+ front_info->num_evt_pairs = num_streams;
+ return 0;
+
+fail:
+ xen_snd_front_evtchnl_free_all(front_info);
+ return ret;
+}
+
+static int evtchnl_publish(struct xenbus_transaction xbt,
+ struct xen_snd_front_evtchnl *channel,
+ const char *path, const char *node_ring,
+ const char *node_chnl)
+{
+ struct xenbus_device *xb_dev = channel->front_info->xb_dev;
+ int ret;
+
+ /* write control channel ring reference */
+ ret = xenbus_printf(xbt, path, node_ring, "%u", channel->gref);
+ if (ret < 0) {
+ dev_err(&xb_dev->dev, "Error writing ring-ref: %d\n", ret);
+ return ret;
+ }
+
+ /* write event channel ring reference */
+ ret = xenbus_printf(xbt, path, node_chnl, "%u", channel->port);
+ if (ret < 0) {
+ dev_err(&xb_dev->dev, "Error writing event channel: %d\n", ret);
+ return ret;
+ }
+
+ return 0;
+}
+
+int xen_snd_front_evtchnl_publish_all(struct xen_snd_front_info *front_info)
+{
+ struct xen_front_cfg_card *cfg = &front_info->cfg;
+ struct xenbus_transaction xbt;
+ int ret, d;
+
+again:
+ ret = xenbus_transaction_start(&xbt);
+ if (ret < 0) {
+ xenbus_dev_fatal(front_info->xb_dev, ret,
+ "starting transaction");
+ return ret;
+ }
+
+ for (d = 0; d < cfg->num_pcm_instances; d++) {
+ struct xen_front_cfg_pcm_instance *pcm_instance;
+ int s, index;
+
+ pcm_instance = &cfg->pcm_instances[d];
+
+ for (s = 0; s < pcm_instance->num_streams_pb; s++) {
+ index = pcm_instance->streams_pb[s].index;
+
+ ret = evtchnl_publish(xbt,
+ &front_info->evt_pairs[index].req,
+ pcm_instance->streams_pb[s].xenstore_path,
+ XENSND_FIELD_RING_REF,
+ XENSND_FIELD_EVT_CHNL);
+ if (ret < 0)
+ goto fail;
+
+ ret = evtchnl_publish(xbt,
+ &front_info->evt_pairs[index].evt,
+ pcm_instance->streams_pb[s].xenstore_path,
+ XENSND_FIELD_EVT_RING_REF,
+ XENSND_FIELD_EVT_EVT_CHNL);
+ if (ret < 0)
+ goto fail;
+ }
+
+ for (s = 0; s < pcm_instance->num_streams_cap; s++) {
+ index = pcm_instance->streams_cap[s].index;
+
+ ret = evtchnl_publish(xbt,
+ &front_info->evt_pairs[index].req,
+ pcm_instance->streams_cap[s].xenstore_path,
+ XENSND_FIELD_RING_REF,
+ XENSND_FIELD_EVT_CHNL);
+ if (ret < 0)
+ goto fail;
+
+ ret = evtchnl_publish(xbt,
+ &front_info->evt_pairs[index].evt,
+ pcm_instance->streams_cap[s].xenstore_path,
+ XENSND_FIELD_EVT_RING_REF,
+ XENSND_FIELD_EVT_EVT_CHNL);
+ if (ret < 0)
+ goto fail;
+ }
+ }
+ ret = xenbus_transaction_end(xbt, 0);
+ if (ret < 0) {
+ if (ret == -EAGAIN)
+ goto again;
+
+ xenbus_dev_fatal(front_info->xb_dev, ret,
+ "completing transaction");
+ goto fail_to_end;
+ }
+ return 0;
+fail:
+ xenbus_transaction_end(xbt, 1);
+fail_to_end:
+ xenbus_dev_fatal(front_info->xb_dev, ret, "writing XenStore");
+ return ret;
+}
+
+void xen_snd_front_evtchnl_pair_set_connected(struct xen_snd_front_evtchnl_pair *evt_pair,
+ bool is_connected)
+{
+ enum xen_snd_front_evtchnl_state state;
+
+ if (is_connected)
+ state = EVTCHNL_STATE_CONNECTED;
+ else
+ state = EVTCHNL_STATE_DISCONNECTED;
+
+ evt_pair->req.state = state;
+ evt_pair->evt.state = state;
+}
+
+void xen_snd_front_evtchnl_pair_clear(struct xen_snd_front_evtchnl_pair *evt_pair)
+{
+ evt_pair->req.evt_next_id = 0;
+ evt_pair->evt.evt_next_id = 0;
+}
+
diff --git a/sound/xen/xen_snd_front_evtchnl.h b/sound/xen/xen_snd_front_evtchnl.h
new file mode 100644
index 000000000000..c4921f469347
--- /dev/null
+++ b/sound/xen/xen_snd_front_evtchnl.h
@@ -0,0 +1,92 @@
+/* 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@xxxxxxxx>
+ */
+
+#ifndef __XEN_SND_FRONT_EVTCHNL_H
+#define __XEN_SND_FRONT_EVTCHNL_H
+
+#include <xen/interface/io/sndif.h>
+
+struct xen_snd_front_info;
+
+#ifndef GRANT_INVALID_REF
+/*
+ * FIXME: usage of grant reference 0 as invalid grant reference:
+ * grant reference 0 is valid, but never exposed to a PV driver,
+ * because of the fact it is already in use/reserved by the PV console.
+ */
+#define GRANT_INVALID_REF 0
+#endif
+
+/* timeout in ms to wait for backend to respond */
+#define VSND_WAIT_BACK_MS 3000
+
+enum xen_snd_front_evtchnl_state {
+ EVTCHNL_STATE_DISCONNECTED,
+ EVTCHNL_STATE_CONNECTED,
+};
+
+enum xen_snd_front_evtchnl_type {
+ EVTCHNL_TYPE_REQ,
+ EVTCHNL_TYPE_EVT,
+};
+
+struct xen_snd_front_evtchnl {
+ struct xen_snd_front_info *front_info;
+ int gref;
+ int port;
+ int irq;
+ int index;
+ /* state of the event channel */
+ enum xen_snd_front_evtchnl_state state;
+ enum xen_snd_front_evtchnl_type type;
+ /* either response id or incoming event id */
+ u16 evt_id;
+ /* next request id or next expected event id */
+ u16 evt_next_id;
+ union {
+ struct {
+ struct xen_sndif_front_ring ring;
+ struct completion completion;
+ /* latest response status */
+ int resp_status;
+ /* serializer for backend IO: request/response */
+ struct mutex req_io_lock;
+ union {
+ struct xensnd_query_hw_param hw_param;
+ } resp;
+ } req;
+ struct {
+ struct xensnd_event_page *page;
+ /* this is needed to handle XENSND_EVT_CUR_POS event */
+ struct snd_pcm_substream *substream;
+ } evt;
+ } u;
+};
+
+struct xen_snd_front_evtchnl_pair {
+ struct xen_snd_front_evtchnl req;
+ struct xen_snd_front_evtchnl evt;
+};
+
+int xen_snd_front_evtchnl_create_all(struct xen_snd_front_info *front_info,
+ int num_streams);
+
+void xen_snd_front_evtchnl_free_all(struct xen_snd_front_info *front_info);
+
+int xen_snd_front_evtchnl_publish_all(struct xen_snd_front_info *front_info);
+
+void xen_snd_front_evtchnl_flush(struct xen_snd_front_evtchnl *evtchnl);
+
+void xen_snd_front_evtchnl_pair_set_connected(struct xen_snd_front_evtchnl_pair *evt_pair,
+ bool is_connected);
+
+void xen_snd_front_evtchnl_pair_clear(struct xen_snd_front_evtchnl_pair *evt_pair);
+
+#endif /* __XEN_SND_FRONT_EVTCHNL_H */
--
2.16.2