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/******************************************************************************
* xenbus_comms.c
*
* Low level code to talks to Xen Store: ringbuffer and event channel.
*
* Copyright (C) 2005 Rusty Russell, IBM Corporation
*
* This file may be 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.
*/
#include <types.h>
#include <wait.h>
#include <mm.h>
#include <hypervisor.h>
#include <events.h>
#include <os.h>
#include <lib.h>
#ifdef XENBUS_COMMS_DEBUG
#define DEBUG(_f, _a...) \
printk("MINI_OS(file=xenbus_comms.c, line=%d) " _f "\n", __LINE__, ## _a)
#else
#define DEBUG(_f, _a...) ((void)0)
#endif
#define RINGBUF_DATASIZE ((PAGE_SIZE / 2) - sizeof(struct ringbuf_head))
struct ringbuf_head
{
u32 write; /* Next place to write to */
u32 read; /* Next place to read from */
u8 flags;
char buf[0];
} __attribute__((packed));
DECLARE_WAIT_QUEUE_HEAD(xb_waitq);
static inline struct ringbuf_head *outbuf(void)
{
return mfn_to_virt(start_info.store_mfn);
}
static inline struct ringbuf_head *inbuf(void)
{
return (struct ringbuf_head *)((char *)mfn_to_virt(start_info.store_mfn) + PAGE_SIZE/2);
}
static void wake_waiting(int port, struct pt_regs *regs)
{
wake_up(&xb_waitq);
}
static int check_buffer(const struct ringbuf_head *h)
{
return (h->write < RINGBUF_DATASIZE && h->read < RINGBUF_DATASIZE);
}
/* We can't fill last byte: would look like empty buffer. */
static void *get_output_chunk(const struct ringbuf_head *h,
void *buf, u32 *len)
{
u32 read_mark;
if (h->read == 0)
read_mark = RINGBUF_DATASIZE - 1;
else
read_mark = h->read - 1;
/* Here to the end of buffer, unless they haven't read some out. */
*len = RINGBUF_DATASIZE - h->write;
if (read_mark >= h->write)
*len = read_mark - h->write;
return (void *)((char *)buf + h->write);
}
static const void *get_input_chunk(const struct ringbuf_head *h,
const void *buf, u32 *len)
{
/* Here to the end of buffer, unless they haven't written some. */
*len = RINGBUF_DATASIZE - h->read;
if (h->write >= h->read)
*len = h->write - h->read;
return (void *)((char *)buf + h->read);
}
static void update_output_chunk(struct ringbuf_head *h, u32 len)
{
h->write += len;
if (h->write == RINGBUF_DATASIZE)
h->write = 0;
}
static void update_input_chunk(struct ringbuf_head *h, u32 len)
{
h->read += len;
if (h->read == RINGBUF_DATASIZE)
h->read = 0;
}
static int output_avail(struct ringbuf_head *out)
{
unsigned int avail;
get_output_chunk(out, out->buf, &avail);
return avail != 0;
}
int xb_write(const void *data, unsigned len)
{
struct ringbuf_head h;
struct ringbuf_head *out = outbuf();
do {
void *dst;
unsigned int avail;
wait_event(xb_waitq, output_avail(out));
/* Read, then check: not that we don't trust store.
* Hell, some of my best friends are daemons. But,
* in this post-911 world... */
h = *out;
mb();
if (!check_buffer(&h)) {
return -1; /* ETERRORIST! */
}
dst = get_output_chunk(&h, out->buf, &avail);
if (avail > len)
avail = len;
memcpy(dst, data, avail);
data = (void *)((char *)data + avail);
len -= avail;
update_output_chunk(out, avail);
notify_via_evtchn(start_info.store_evtchn);
} while (len != 0);
return 0;
}
int xs_input_avail(void)
{
unsigned int avail;
struct ringbuf_head *in = inbuf();
get_input_chunk(in, in->buf, &avail);
return avail != 0;
}
int xb_read(void *data, unsigned len)
{
struct ringbuf_head h;
struct ringbuf_head *in = inbuf();
int was_full;
while (len != 0) {
unsigned int avail;
const char *src;
wait_event(xb_waitq, xs_input_avail());
h = *in;
mb();
if (!check_buffer(&h)) {
return -1;
}
src = get_input_chunk(&h, in->buf, &avail);
if (avail > len)
avail = len;
was_full = !output_avail(&h);
memcpy(data, src, avail);
data = (void *)((char *)data + avail);
len -= avail;
update_input_chunk(in, avail);
DEBUG("Finished read of %i bytes (%i to go)\n", avail, len);
/* If it was full, tell them we've taken some. */
if (was_full)
notify_via_evtchn(start_info.store_evtchn);
}
/* If we left something, wake watch thread to deal with it. */
if (xs_input_avail())
wake_up(&xb_waitq);
return 0;
}
/* Set up interrupt handler off store event channel. */
int xb_init_comms(void)
{
printk("Init xenbus comms, store event channel %d\n", start_info.store_evtchn);
if (!start_info.store_evtchn)
return 0;
printk("Binding virq\n");
bind_evtchn(start_info.store_evtchn, &wake_waiting);
/* FIXME zero out page -- domain builder should probably do this*/
memset(mfn_to_virt(start_info.store_mfn), 0, PAGE_SIZE);
notify_via_evtchn(start_info.store_evtchn);
return 0;
}
void xb_suspend_comms(void)
{
if (!start_info.store_evtchn)
return;
// TODO
//unbind_evtchn_from_irqhandler(xen_start_info.store_evtchn, &xb_waitq);
}
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