| /****************************************************************************** |
| * xenbus_comms.c |
| * |
| * Low level code to talks to Xen Store: ringbuffer and event channel. |
| * |
| * Copyright (C) 2005 Rusty Russell, IBM Corporation |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License version 2 |
| * as published by the Free Software Foundation; or, when distributed |
| * separately from the Linux kernel or incorporated into other |
| * software packages, subject to the following license: |
| * |
| * Permission is hereby granted, free of charge, to any person obtaining a copy |
| * of this source file (the "Software"), to deal in the Software without |
| * restriction, including without limitation the rights to use, copy, modify, |
| * merge, publish, distribute, sublicense, and/or sell copies of the Software, |
| * and to permit persons to whom the Software is furnished to do so, subject to |
| * the following conditions: |
| * |
| * The above copyright notice and this permission notice shall be included in |
| * all copies or substantial portions of the Software. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
| * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS |
| * IN THE SOFTWARE. |
| */ |
| |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| |
| #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.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 irqreturn_t wake_waiting(int irq, void *unused) |
| { |
| if (unlikely(xenstored_ready == 0)) { |
| xenstored_ready = 1; |
| schedule_work(&probe_work); |
| } |
| |
| wake_up(&xb_waitq); |
| return IRQ_HANDLED; |
| } |
| |
| static int check_indexes(XENSTORE_RING_IDX cons, XENSTORE_RING_IDX prod) |
| { |
| return ((prod - cons) <= XENSTORE_RING_SIZE); |
| } |
| |
| static void *get_output_chunk(XENSTORE_RING_IDX cons, |
| XENSTORE_RING_IDX prod, |
| char *buf, uint32_t *len) |
| { |
| *len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(prod); |
| if ((XENSTORE_RING_SIZE - (prod - cons)) < *len) |
| *len = XENSTORE_RING_SIZE - (prod - cons); |
| return buf + MASK_XENSTORE_IDX(prod); |
| } |
| |
| static const void *get_input_chunk(XENSTORE_RING_IDX cons, |
| XENSTORE_RING_IDX prod, |
| const char *buf, uint32_t *len) |
| { |
| *len = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(cons); |
| if ((prod - cons) < *len) |
| *len = prod - 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 number of bytes written or -err. |
| */ |
| static int xb_write(const void *data, unsigned int len) |
| { |
| struct xenstore_domain_interface *intf = xen_store_interface; |
| XENSTORE_RING_IDX cons, prod; |
| unsigned int bytes = 0; |
| |
| while (len != 0) { |
| void *dst; |
| unsigned int avail; |
| |
| /* Read indexes, then verify. */ |
| cons = intf->req_cons; |
| prod = intf->req_prod; |
| if (!check_indexes(cons, prod)) { |
| 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) |
| continue; |
| if (avail > len) |
| avail = len; |
| |
| 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. */ |
| if (prod <= intf->req_cons) |
| notify_remote_via_evtchn(xen_store_evtchn); |
| } |
| |
| return bytes; |
| } |
| |
| static int xb_data_to_read(void) |
| { |
| struct xenstore_domain_interface *intf = xen_store_interface; |
| return (intf->rsp_cons != intf->rsp_prod); |
| } |
| |
| static int xb_read(void *data, unsigned int len) |
| { |
| struct xenstore_domain_interface *intf = xen_store_interface; |
| XENSTORE_RING_IDX cons, prod; |
| unsigned int bytes = 0; |
| |
| while (len != 0) { |
| unsigned int avail; |
| const char *src; |
| |
| /* 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; |
| } |
| |
| src = get_input_chunk(cons, prod, intf->rsp, &avail); |
| if (avail == 0) |
| continue; |
| if (avail > len) |
| avail = len; |
| |
| /* Must read data /after/ reading the producer index. */ |
| virt_rmb(); |
| |
| 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; |
| |
| /* Implies mb(): other side will see the updated consumer. */ |
| 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; |
| } |
| |
| /** |
| * xb_init_comms - Set up interrupt handler off store event channel. |
| */ |
| int xb_init_comms(void) |
| { |
| struct xenstore_domain_interface *intf = xen_store_interface; |
| |
| if (intf->req_prod != intf->req_cons) |
| pr_err("request ring is not quiescent (%08x:%08x)!\n", |
| intf->req_cons, intf->req_prod); |
| |
| if (intf->rsp_prod != intf->rsp_cons) { |
| pr_warn("response ring is not quiescent (%08x:%08x): fixing up\n", |
| intf->rsp_cons, intf->rsp_prod); |
| /* breaks kdump */ |
| if (!reset_devices) |
| intf->rsp_cons = intf->rsp_prod; |
| } |
| |
| if (xenbus_irq) { |
| /* Already have an irq; assume we're resuming */ |
| 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) { |
| pr_err("request irq failed %i\n", err); |
| return err; |
| } |
| |
| 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; |
| } |
| |
| void xb_deinit_comms(void) |
| { |
| unbind_from_irqhandler(xenbus_irq, &xb_waitq); |
| xenbus_irq = 0; |
| } |