diff options
Diffstat (limited to 'drivers/xen/xenbus/xenbus_comms.c')
-rw-r--r-- | drivers/xen/xenbus/xenbus_comms.c | 309 |
1 files changed, 277 insertions, 32 deletions
diff --git a/drivers/xen/xenbus/xenbus_comms.c b/drivers/xen/xenbus/xenbus_comms.c index ecdecce80a6c..856ada5d39c9 100644 --- a/drivers/xen/xenbus/xenbus_comms.c +++ b/drivers/xen/xenbus/xenbus_comms.c @@ -34,19 +34,31 @@ #include <linux/wait.h> #include <linux/interrupt.h> +#include <linux/kthread.h> #include <linux/sched.h> #include <linux/err.h> #include <xen/xenbus.h> #include <asm/xen/hypervisor.h> #include <xen/events.h> #include <xen/page.h> -#include "xenbus_comms.h" +#include "xenbus.h" + +/* A list of replies. Currently only one will ever be outstanding. */ +LIST_HEAD(xs_reply_list); + +/* A list of write requests. */ +LIST_HEAD(xb_write_list); +DECLARE_WAIT_QUEUE_HEAD(xb_waitq); +DEFINE_MUTEX(xb_write_mutex); + +/* Protect xenbus reader thread against save/restore. */ +DEFINE_MUTEX(xs_response_mutex); static int xenbus_irq; +static struct task_struct *xenbus_task; static DECLARE_WORK(probe_work, xenbus_probe); -static DECLARE_WAIT_QUEUE_HEAD(xb_waitq); static irqreturn_t wake_waiting(int irq, void *unused) { @@ -84,30 +96,31 @@ static const void *get_input_chunk(XENSTORE_RING_IDX cons, return buf + MASK_XENSTORE_IDX(cons); } +static int xb_data_to_write(void) +{ + struct xenstore_domain_interface *intf = xen_store_interface; + + return (intf->req_prod - intf->req_cons) != XENSTORE_RING_SIZE && + !list_empty(&xb_write_list); +} + /** * xb_write - low level write * @data: buffer to send * @len: length of buffer * - * Returns 0 on success, error otherwise. + * Returns number of bytes written or -err. */ -int xb_write(const void *data, unsigned len) +static int xb_write(const void *data, unsigned int len) { struct xenstore_domain_interface *intf = xen_store_interface; XENSTORE_RING_IDX cons, prod; - int rc; + unsigned int bytes = 0; while (len != 0) { void *dst; unsigned int avail; - rc = wait_event_interruptible( - xb_waitq, - (intf->req_prod - intf->req_cons) != - XENSTORE_RING_SIZE); - if (rc < 0) - return rc; - /* Read indexes, then verify. */ cons = intf->req_cons; prod = intf->req_prod; @@ -115,6 +128,11 @@ int xb_write(const void *data, unsigned len) intf->req_cons = intf->req_prod = 0; return -EIO; } + if (!xb_data_to_write()) + return bytes; + + /* Must write data /after/ reading the consumer index. */ + virt_mb(); dst = get_output_chunk(cons, prod, intf->req, &avail); if (avail == 0) @@ -122,52 +140,45 @@ int xb_write(const void *data, unsigned len) if (avail > len) avail = len; - /* Must write data /after/ reading the consumer index. */ - virt_mb(); - memcpy(dst, data, avail); data += avail; len -= avail; + bytes += avail; /* Other side must not see new producer until data is there. */ virt_wmb(); intf->req_prod += avail; /* Implies mb(): other side will see the updated producer. */ - notify_remote_via_evtchn(xen_store_evtchn); + if (prod <= intf->req_cons) + notify_remote_via_evtchn(xen_store_evtchn); } - return 0; + return bytes; } -int xb_data_to_read(void) +static int xb_data_to_read(void) { struct xenstore_domain_interface *intf = xen_store_interface; return (intf->rsp_cons != intf->rsp_prod); } -int xb_wait_for_data_to_read(void) -{ - return wait_event_interruptible(xb_waitq, xb_data_to_read()); -} - -int xb_read(void *data, unsigned len) +static int xb_read(void *data, unsigned int len) { struct xenstore_domain_interface *intf = xen_store_interface; XENSTORE_RING_IDX cons, prod; - int rc; + unsigned int bytes = 0; while (len != 0) { unsigned int avail; const char *src; - rc = xb_wait_for_data_to_read(); - if (rc < 0) - return rc; - /* Read indexes, then verify. */ cons = intf->rsp_cons; prod = intf->rsp_prod; + if (cons == prod) + return bytes; + if (!check_indexes(cons, prod)) { intf->rsp_cons = intf->rsp_prod = 0; return -EIO; @@ -185,17 +196,243 @@ int xb_read(void *data, unsigned len) memcpy(data, src, avail); data += avail; len -= avail; + bytes += avail; /* Other side must not see free space until we've copied out */ virt_mb(); intf->rsp_cons += avail; - pr_debug("Finished read of %i bytes (%i to go)\n", avail, len); - /* Implies mb(): other side will see the updated consumer. */ - notify_remote_via_evtchn(xen_store_evtchn); + if (intf->rsp_prod - cons >= XENSTORE_RING_SIZE) + notify_remote_via_evtchn(xen_store_evtchn); + } + + return bytes; +} + +static int process_msg(void) +{ + static struct { + struct xsd_sockmsg msg; + char *body; + union { + void *alloc; + struct xs_watch_event *watch; + }; + bool in_msg; + bool in_hdr; + unsigned int read; + } state; + struct xb_req_data *req; + int err; + unsigned int len; + + if (!state.in_msg) { + state.in_msg = true; + state.in_hdr = true; + state.read = 0; + + /* + * We must disallow save/restore while reading a message. + * A partial read across s/r leaves us out of sync with + * xenstored. + * xs_response_mutex is locked as long as we are processing one + * message. state.in_msg will be true as long as we are holding + * the lock here. + */ + mutex_lock(&xs_response_mutex); + + if (!xb_data_to_read()) { + /* We raced with save/restore: pending data 'gone'. */ + mutex_unlock(&xs_response_mutex); + state.in_msg = false; + return 0; + } + } + + if (state.in_hdr) { + if (state.read != sizeof(state.msg)) { + err = xb_read((void *)&state.msg + state.read, + sizeof(state.msg) - state.read); + if (err < 0) + goto out; + state.read += err; + if (state.read != sizeof(state.msg)) + return 0; + if (state.msg.len > XENSTORE_PAYLOAD_MAX) { + err = -EINVAL; + goto out; + } + } + + len = state.msg.len + 1; + if (state.msg.type == XS_WATCH_EVENT) + len += sizeof(*state.watch); + + state.alloc = kmalloc(len, GFP_NOIO | __GFP_HIGH); + if (!state.alloc) + return -ENOMEM; + + if (state.msg.type == XS_WATCH_EVENT) + state.body = state.watch->body; + else + state.body = state.alloc; + state.in_hdr = false; + state.read = 0; + } + + err = xb_read(state.body + state.read, state.msg.len - state.read); + if (err < 0) + goto out; + + state.read += err; + if (state.read != state.msg.len) + return 0; + + state.body[state.msg.len] = '\0'; + + if (state.msg.type == XS_WATCH_EVENT) { + state.watch->len = state.msg.len; + err = xs_watch_msg(state.watch); + } else { + err = -ENOENT; + mutex_lock(&xb_write_mutex); + list_for_each_entry(req, &xs_reply_list, list) { + if (req->msg.req_id == state.msg.req_id) { + if (req->state == xb_req_state_wait_reply) { + req->msg.type = state.msg.type; + req->msg.len = state.msg.len; + req->body = state.body; + req->state = xb_req_state_got_reply; + list_del(&req->list); + req->cb(req); + } else { + list_del(&req->list); + kfree(req); + } + err = 0; + break; + } + } + mutex_unlock(&xb_write_mutex); + if (err) + goto out; } + mutex_unlock(&xs_response_mutex); + + state.in_msg = false; + state.alloc = NULL; + return err; + + out: + mutex_unlock(&xs_response_mutex); + state.in_msg = false; + kfree(state.alloc); + state.alloc = NULL; + return err; +} + +static int process_writes(void) +{ + static struct { + struct xb_req_data *req; + int idx; + unsigned int written; + } state; + void *base; + unsigned int len; + int err = 0; + + if (!xb_data_to_write()) + return 0; + + mutex_lock(&xb_write_mutex); + + if (!state.req) { + state.req = list_first_entry(&xb_write_list, + struct xb_req_data, list); + state.idx = -1; + state.written = 0; + } + + if (state.req->state == xb_req_state_aborted) + goto out_err; + + while (state.idx < state.req->num_vecs) { + if (state.idx < 0) { + base = &state.req->msg; + len = sizeof(state.req->msg); + } else { + base = state.req->vec[state.idx].iov_base; + len = state.req->vec[state.idx].iov_len; + } + err = xb_write(base + state.written, len - state.written); + if (err < 0) + goto out_err; + state.written += err; + if (state.written != len) + goto out; + + state.idx++; + state.written = 0; + } + + list_del(&state.req->list); + state.req->state = xb_req_state_wait_reply; + list_add_tail(&state.req->list, &xs_reply_list); + state.req = NULL; + + out: + mutex_unlock(&xb_write_mutex); + + return 0; + + out_err: + state.req->msg.type = XS_ERROR; + state.req->err = err; + list_del(&state.req->list); + if (state.req->state == xb_req_state_aborted) + kfree(state.req); + else { + state.req->state = xb_req_state_got_reply; + wake_up(&state.req->wq); + } + + mutex_unlock(&xb_write_mutex); + + state.req = NULL; + + return err; +} + +static int xb_thread_work(void) +{ + return xb_data_to_read() || xb_data_to_write(); +} + +static int xenbus_thread(void *unused) +{ + int err; + + while (!kthread_should_stop()) { + if (wait_event_interruptible(xb_waitq, xb_thread_work())) + continue; + + err = process_msg(); + if (err == -ENOMEM) + schedule(); + else if (err) + pr_warn_ratelimited("error %d while reading message\n", + err); + + err = process_writes(); + if (err) + pr_warn_ratelimited("error %d while writing message\n", + err); + } + + xenbus_task = NULL; return 0; } @@ -223,6 +460,7 @@ int xb_init_comms(void) rebind_evtchn_irq(xen_store_evtchn, xenbus_irq); } else { int err; + err = bind_evtchn_to_irqhandler(xen_store_evtchn, wake_waiting, 0, "xenbus", &xb_waitq); if (err < 0) { @@ -231,6 +469,13 @@ int xb_init_comms(void) } xenbus_irq = err; + + if (!xenbus_task) { + xenbus_task = kthread_run(xenbus_thread, NULL, + "xenbus"); + if (IS_ERR(xenbus_task)) + return PTR_ERR(xenbus_task); + } } return 0; |