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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: [PATCH 3/3] libvchan: interdomain communications library
On Mon, 2011-09-19 at 23:43 +0100, Daniel De Graaf wrote:
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
LGPL v2 isn't all that widely used (I had some flaw or other which I
don't recall and have failed to google up).
Most of our libraries are LGPL v2.1 not v2 as well. Since you have the
"or later version" clause I think it should be trivial to uprev? (by the
same token it perhaps doesn't matter, but fewer licenses in use at once
seems useful)
Ian.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> 02110-1301 USA
> + *
> + * @section DESCRIPTION
> + *
> + * This file contains the setup code used to establish the ring buffer.
> + */
> +
> +#include <sys/types.h>
> +#include <sys/mman.h>
> +#include <sys/ioctl.h>
> +#include <sys/user.h>
> +#include <stdlib.h>
> +#include <stdio.h>
> +#include <stdint.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <fcntl.h>
> +
> +#include <xs.h>
> +#include <xen/sys/evtchn.h>
> +#include <xen/sys/gntalloc.h>
> +#include <xen/sys/gntdev.h>
> +#include <libxenvchan.h>
> +
> +#ifndef PAGE_SHIFT
> +#define PAGE_SHIFT 12
> +#endif
> +
> +#ifndef PAGE_SIZE
> +#define PAGE_SIZE 4096
> +#endif
> +
> +#ifndef offsetof
> +#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
> +#endif
> +
> +#define max(a,b) ((a > b) ? a : b)
> +
> +static int init_gnt_srv(struct libvchan *ctrl)
> +{
> + int pages_left = ctrl->read.order >= PAGE_SHIFT ? 1 <<
> (ctrl->read.order - PAGE_SHIFT) : 0;
> + int pages_right = ctrl->write.order >= PAGE_SHIFT ? 1 <<
> (ctrl->write.order - PAGE_SHIFT) : 0;
> + uint32_t ring_ref = -1;
> + void *ring;
> +
> + ring = xc_gntshr_share_page_notify(ctrl->gntshr,
> ctrl->other_domain_id,
> + &ring_ref, 1, offsetof(struct vchan_interface,
> srv_live),
> + ctrl->event_port, NULL);
> +
> + if (!ring)
> + goto out;
> +
> + memset(ring, 0, PAGE_SIZE);
> +
> + ctrl->ring = ring;
> + ctrl->read.shr = &ctrl->ring->left;
> + ctrl->write.shr = &ctrl->ring->right;
> + ctrl->ring->left_order = ctrl->read.order;
> + ctrl->ring->right_order = ctrl->write.order;
> + ctrl->ring->cli_live = 2;
> + ctrl->ring->srv_live = 1;
> + ctrl->ring->cli_notify = VCHAN_NOTIFY_WRITE;
> +
> + if (ctrl->read.order == 10) {
> + ctrl->read.buffer = ((void*)ctrl->ring) + 1024;
> + } else if (ctrl->read.order == 11) {
> + ctrl->read.buffer = ((void*)ctrl->ring) + 2048;
> + } else {
> + ctrl->read.buffer = xc_gntshr_share_pages(ctrl->gntshr,
> ctrl->other_domain_id,
> + pages_left, ctrl->ring->grants, 1);
> + if (!ctrl->read.buffer)
> + goto out_ring;
> + }
> +
> + if (ctrl->write.order == 10) {
> + ctrl->write.buffer = ((void*)ctrl->ring) + 1024;
> + } else if (ctrl->write.order == 11) {
> + ctrl->write.buffer = ((void*)ctrl->ring) + 2048;
> + } else {
> + ctrl->write.buffer = xc_gntshr_share_pages(ctrl->gntshr,
> ctrl->other_domain_id,
> + pages_right, ctrl->ring->grants + pages_left, 1);
> + if (!ctrl->write.buffer)
> + goto out_unmap_left;
> + }
> +
> +out:
> + return ring_ref;
> +out_unmap_left:
> + if (ctrl->read.order > 11)
> + xc_gntshr_munmap(ctrl->gntshr, ctrl->read.buffer, pages_left
> * PAGE_SIZE);
> +out_ring:
> + xc_gntshr_munmap(ctrl->gntshr, ring, PAGE_SIZE);
> + ring_ref = -1;
> + ctrl->ring = NULL;
> + ctrl->write.order = ctrl->read.order = 0;
> + goto out;
> +}
> +
> +static int init_gnt_cli(struct libvchan *ctrl, uint32_t ring_ref)
> +{
> + int rv = -1;
> + uint32_t *grants;
> +
> + ctrl->ring = xc_gnttab_map_grant_ref_notify(ctrl->gnttab,
> + ctrl->other_domain_id, ring_ref,
> + offsetof(struct vchan_interface, cli_live), ctrl->event_port,
> + NULL);
> +
> + if (!ctrl->ring)
> + goto out;
> +
> + ctrl->write.order = ctrl->ring->left_order;
> + ctrl->read.order = ctrl->ring->right_order;
> + ctrl->write.shr = &ctrl->ring->left;
> + ctrl->read.shr = &ctrl->ring->right;
> + if (ctrl->write.order < 10 || ctrl->write.order > 24)
> + goto out_unmap_ring;
> + if (ctrl->read.order < 10 || ctrl->read.order > 24)
> + goto out_unmap_ring;
> + if (ctrl->read.order == ctrl->write.order && ctrl->read.order < 12)
> + goto out_unmap_ring;
> +
> + grants = ctrl->ring->grants;
> +
> + if (ctrl->write.order == 10) {
> + ctrl->write.buffer = ((void*)ctrl->ring) + 1024;
> + } else if (ctrl->write.order == 11) {
> + ctrl->write.buffer = ((void*)ctrl->ring) + 2048;
> + } else {
> + int pages_left = 1 << (ctrl->write.order - PAGE_SHIFT);
> + ctrl->write.buffer =
> xc_gnttab_map_domain_grant_refs(ctrl->gnttab,
> + pages_left, ctrl->other_domain_id, grants,
> PROT_READ|PROT_WRITE);
> + if (!ctrl->write.buffer)
> + goto out_unmap_ring;
> + grants += pages_left;
> + }
> +
> + if (ctrl->read.order == 10) {
> + ctrl->read.buffer = ((void*)ctrl->ring) + 1024;
> + } else if (ctrl->read.order == 11) {
> + ctrl->read.buffer = ((void*)ctrl->ring) + 2048;
> + } else {
> + int pages_right = 1 << (ctrl->read.order - PAGE_SHIFT);
> + ctrl->read.buffer =
> xc_gnttab_map_domain_grant_refs(ctrl->gnttab,
> + pages_right, ctrl->other_domain_id, grants,
> PROT_READ);
> + if (!ctrl->read.buffer)
> + goto out_unmap_left;
> + }
> +
> + rv = 0;
> + out:
> + return rv;
> + out_unmap_left:
> + if (ctrl->write.order >= PAGE_SHIFT)
> + xc_gnttab_munmap(ctrl->gnttab, ctrl->write.buffer,
> + 1 << ctrl->write.order);
> + out_unmap_ring:
> + xc_gnttab_munmap(ctrl->gnttab, ctrl->ring, PAGE_SIZE);
> + ctrl->ring = 0;
> + ctrl->write.order = ctrl->read.order = 0;
> + rv = -1;
> + goto out;
> +}
> +
> +static int init_evt_srv(struct libvchan *ctrl, xentoollog_logger *logger)
> +{
> + ctrl->event = xc_evtchn_open(logger, 0);
> + if (!ctrl->event)
> + return -1;
> + ctrl->event_port = xc_evtchn_bind_unbound_port(ctrl->event,
> ctrl->other_domain_id);
> + if (ctrl->event_port < 0)
> + return -1;
> + if (xc_evtchn_unmask(ctrl->event, ctrl->event_port))
> + return -1;
> + return 0;
> +}
> +
> +static int init_xs_srv(struct libvchan *ctrl, int ring_ref)
> +{
> + int ret = -1;
> + struct xs_handle *xs;
> + struct xs_permissions perms[2];
> + char buf[64];
> + char ref[16];
> + char* domid_str = NULL;
> + xs = xs_domain_open();
> + if (!xs)
> + goto fail;
> + domid_str = xs_read(xs, 0, "domid", NULL);
> + if (!domid_str)
> + goto fail_xs_open;
> +
> + // owner domain is us
> + perms[0].id = atoi(domid_str);
> + // permissions for domains not listed = none
> + perms[0].perms = XS_PERM_NONE;
> + // other domains
> + perms[1].id = ctrl->other_domain_id;
> + perms[1].perms = XS_PERM_READ;
> +
> + snprintf(ref, sizeof ref, "%d", ring_ref);
> + snprintf(buf, sizeof buf, "data/vchan/%d/%d/ring-ref",
> ctrl->other_domain_id, ctrl->device_number);
> + if (!xs_write(xs, 0, buf, ref, strlen(ref)))
> + goto fail_xs_open;
> + if (!xs_set_permissions(xs, 0, buf, perms, 2))
> + goto fail_xs_open;
> +
> + snprintf(ref, sizeof ref, "%d", ctrl->event_port);
> + snprintf(buf, sizeof buf, "data/vchan/%d/%d/event-channel",
> ctrl->other_domain_id, ctrl->device_number);
> + if (!xs_write(xs, 0, buf, ref, strlen(ref)))
> + goto fail_xs_open;
> + if (!xs_set_permissions(xs, 0, buf, perms, 2))
> + goto fail_xs_open;
> +
> + ret = 0;
> + fail_xs_open:
> + free(domid_str);
> + xs_daemon_close(xs);
> + fail:
> + return ret;
> +}
> +
> +static int min_order(size_t siz)
> +{
> + int rv = PAGE_SHIFT;
> + while (siz > (1 << rv))
> + rv++;
> + return rv;
> +}
> +
> +struct libvchan *libvchan_server_init(xentoollog_logger *logger, int domain,
> int devno, size_t left_min, size_t right_min)
> +{
> + // if you go over this size, you'll have too many grants to fit in
> the shared page.
> + size_t MAX_RING_SIZE = 256 * PAGE_SIZE;
> + struct libvchan *ctrl;
> + int ring_ref;
> + if (left_min > MAX_RING_SIZE || right_min > MAX_RING_SIZE)
> + return 0;
> +
> + ctrl = malloc(sizeof(*ctrl));
> + if (!ctrl)
> + return 0;
> +
> + ctrl->other_domain_id = domain;
> + ctrl->device_number = devno;
> + ctrl->ring = NULL;
> + ctrl->event = NULL;
> + ctrl->is_server = 1;
> + ctrl->server_persist = 0;
> +
> + ctrl->read.order = min_order(left_min);
> + ctrl->write.order = min_order(right_min);
> +
> + // if we can avoid allocating extra pages by using in-page rings, do
> so
> +#define MAX_SMALL_RING 1024
> +#define MAX_LARGE_RING 2048
> + if (left_min <= MAX_SMALL_RING && right_min <= MAX_LARGE_RING) {
> + ctrl->read.order = 10;
> + ctrl->write.order = 11;
> + } else if (left_min <= MAX_LARGE_RING && right_min <= MAX_SMALL_RING)
> {
> + ctrl->read.order = 11;
> + ctrl->write.order = 10;
> + } else if (left_min <= MAX_LARGE_RING) {
> + ctrl->read.order = 11;
> + } else if (right_min <= MAX_LARGE_RING) {
> + ctrl->write.order = 11;
> + }
> +
> + ctrl->gntshr = xc_gntshr_open(logger, 0);
> + if (!ctrl->gntshr)
> + goto out;
> +
> + if (init_evt_srv(ctrl, logger))
> + goto out;
> + ring_ref = init_gnt_srv(ctrl);
> + if (ring_ref < 0)
> + goto out;
> + if (init_xs_srv(ctrl, ring_ref))
> + goto out;
> + return ctrl;
> +out:
> + libvchan_close(ctrl);
> + return 0;
> +}
> +
> +static int init_evt_cli(struct libvchan *ctrl, xentoollog_logger *logger)
> +{
> + ctrl->event = xc_evtchn_open(logger, 0);
> + if (!ctrl->event)
> + return -1;
> + ctrl->event_port = xc_evtchn_bind_interdomain(ctrl->event,
> + ctrl->other_domain_id, ctrl->event_port);
> + if (ctrl->event_port < 0)
> + return -1;
> + xc_evtchn_unmask(ctrl->event, ctrl->event_port);
> + return 0;
> +}
> +
> +
> +struct libvchan *libvchan_client_init(xentoollog_logger *logger, int domain,
> int devno)
> +{
> + struct libvchan *ctrl = malloc(sizeof(struct libvchan));
> + struct xs_handle *xs = NULL;
> + char buf[64];
> + char *ref;
> + int ring_ref;
> + unsigned int len;
> + char* domid_str = NULL;
> +
> + if (!ctrl)
> + return 0;
> + ctrl->other_domain_id = domain;
> + ctrl->device_number = devno;
> + ctrl->ring = NULL;
> + ctrl->event = NULL;
> + ctrl->write.order = ctrl->read.order = 0;
> + ctrl->is_server = 0;
> +
> + xs = xs_daemon_open();
> + if (!xs)
> + xs = xs_domain_open();
> + if (!xs)
> + goto fail;
> +
> + domid_str = xs_read(xs, 0, "domid", NULL);
> + if (!domid_str)
> + goto fail;
> +
> +// find xenstore entry
> + snprintf(buf, sizeof buf,
> "/local/domain/%d/data/vchan/%s/%d/ring-ref",
> + ctrl->other_domain_id, domid_str, ctrl->device_number);
> + ref = xs_read(xs, 0, buf, &len);
> + if (!ref)
> + goto fail;
> + ring_ref = atoi(ref);
> + free(ref);
> + if (!ring_ref)
> + goto fail;
> + snprintf(buf, sizeof buf,
> "/local/domain/%d/data/vchan/%s/%d/event-channel",
> + ctrl->other_domain_id, domid_str, ctrl->device_number);
> + ref = xs_read(xs, 0, buf, &len);
> + if (!ref)
> + goto fail;
> + ctrl->event_port = atoi(ref);
> + free(ref);
> + if (!ctrl->event_port)
> + goto fail;
> +
> + ctrl->gnttab = xc_gnttab_open(logger, 0);
> + if (!ctrl->gnttab)
> + goto out;
> +
> +// set up event channel
> + if (init_evt_cli(ctrl, logger))
> + goto fail;
> +
> +// set up shared page(s)
> + if (init_gnt_cli(ctrl, ring_ref))
> + goto fail;
> +
> + ctrl->ring->cli_live = 1;
> + ctrl->ring->srv_notify = VCHAN_NOTIFY_WRITE;
> +
> + out:
> + free(domid_str);
> + if (xs)
> + xs_daemon_close(xs);
> + return ctrl;
> + fail:
> + libvchan_close(ctrl);
> + ctrl = NULL;
> + goto out;
> +}
> diff --git a/tools/libvchan/io.c b/tools/libvchan/io.c
> new file mode 100644
> index 0000000..08d5dcf
> --- /dev/null
> +++ b/tools/libvchan/io.c
> @@ -0,0 +1,375 @@
> +/**
> + * @file
> + * @section AUTHORS
> + *
> + * Copyright (C) 2010 Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
> + *
> + * Authors:
> + * Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
> + * Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
> + *
> + * @section LICENSE
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> 02110-1301 USA
> + *
> + * @section DESCRIPTION
> + *
> + * This file contains the communications interface built on the ring buffer.
> + */
> +
> +#include <sys/types.h>
> +#include <sys/mman.h>
> +#include <sys/ioctl.h>
> +#include <sys/uio.h>
> +#include <stdlib.h>
> +#include <stdint.h>
> +#include <string.h>
> +#include <unistd.h>
> +
> +#include <xenctrl.h>
> +#include <libxenvchan.h>
> +
> +#ifndef PAGE_SHIFT
> +#define PAGE_SHIFT 12
> +#endif
> +
> +#ifndef PAGE_SIZE
> +#define PAGE_SIZE 4096
> +#endif
> +
> +// allow vchan data to be easily observed in strace by doing a
> +// writev() to FD -1 with the data being read/written.
> +#ifndef VCHAN_DEBUG
> +#define VCHAN_DEBUG 0
> +#endif
> +
> +#define barrier() asm volatile("" ::: "memory")
> +
> +
> +static inline uint32_t rd_prod(struct libvchan *ctrl)
> +{
> + return ctrl->read.shr->prod;
> +}
> +
> +static inline uint32_t* _rd_cons(struct libvchan *ctrl)
> +{
> + return &ctrl->read.shr->cons;
> +}
> +#define rd_cons(x) (*_rd_cons(x))
> +
> +static inline uint32_t* _wr_prod(struct libvchan *ctrl)
> +{
> + return &ctrl->write.shr->prod;
> +}
> +#define wr_prod(x) (*_wr_prod(x))
> +
> +static inline uint32_t wr_cons(struct libvchan *ctrl)
> +{
> + return ctrl->write.shr->cons;
> +}
> +
> +static inline const void* rd_ring(struct libvchan *ctrl)
> +{
> + return ctrl->read.buffer;
> +}
> +
> +static inline void* wr_ring(struct libvchan *ctrl)
> +{
> + return ctrl->write.buffer;
> +}
> +
> +static inline uint32_t wr_ring_size(struct libvchan *ctrl)
> +{
> + return (1 << ctrl->write.order);
> +}
> +
> +static inline uint32_t rd_ring_size(struct libvchan *ctrl)
> +{
> + return (1 << ctrl->read.order);
> +}
> +
> +static inline void request_notify(struct libvchan *ctrl, uint8_t bit)
> +{
> + uint8_t *notify = ctrl->is_server ? &ctrl->ring->cli_notify :
> &ctrl->ring->srv_notify;
> + __sync_or_and_fetch(notify, bit);
> +}
> +
> +static inline int send_notify(struct libvchan *ctrl, uint8_t bit)
> +{
> + uint8_t *notify = ctrl->is_server ? &ctrl->ring->srv_notify :
> &ctrl->ring->cli_notify;
> + uint8_t prev = __sync_fetch_and_and(notify, ~bit);
> + if (prev & bit)
> + return xc_evtchn_notify(ctrl->event, ctrl->event_port);
> + else
> + return 0;
> +}
> +
> +/**
> + * Get the amount of buffer space available and enable notifications if
> needed.
> + */
> +static inline int fast_get_data_ready(struct libvchan *ctrl, size_t request)
> +{
> + int ready = rd_prod(ctrl) - rd_cons(ctrl);
> + if (ready >= request)
> + return ready;
> + /* We plan to consume all data; please tell us if you send more */
> + request_notify(ctrl, VCHAN_NOTIFY_WRITE);
> + /*
> + * If the writer moved rd_prod after our read but before request, we
> + * will not get notified even though the actual amount of data ready
> is
> + * above request. Reread rd_prod to cover this case.
> + */
> + return rd_prod(ctrl) - rd_cons(ctrl);
> +}
> +
> +int libvchan_data_ready(struct libvchan *ctrl)
> +{
> + /* Since this value is being used outside libvchan, request
> notification
> + * when it changes
> + */
> + request_notify(ctrl, VCHAN_NOTIFY_WRITE);
> + return rd_prod(ctrl) - rd_cons(ctrl);
> +}
> +
> +/**
> + * Get the amount of buffer space available and enable notifications if
> needed.
> + */
> +static inline int fast_get_buffer_space(struct libvchan *ctrl, size_t
> request)
> +{
> + int ready = wr_ring_size(ctrl) - (wr_prod(ctrl) - wr_cons(ctrl));
> + if (ready >= request)
> + return ready;
> + /* We plan to fill the buffer; please tell us when you've read it */
> + request_notify(ctrl, VCHAN_NOTIFY_READ);
> + /*
> + * If the reader moved wr_cons after our read but before request, we
> + * will not get notified even though the actual amount of buffer space
> + * is above request. Reread wr_cons to cover this case.
> + */
> + return wr_ring_size(ctrl) - (wr_prod(ctrl) - wr_cons(ctrl));
> +}
> +
> +int libvchan_buffer_space(struct libvchan *ctrl)
> +{
> + /* Since this value is being used outside libvchan, request
> notification
> + * when it changes
> + */
> + request_notify(ctrl, VCHAN_NOTIFY_READ);
> + return wr_ring_size(ctrl) - (wr_prod(ctrl) - wr_cons(ctrl));
> +}
> +
> +int libvchan_wait(struct libvchan *ctrl)
> +{
> + int ret = xc_evtchn_pending(ctrl->event);
> + if (ret < 0)
> + return -1;
> + xc_evtchn_unmask(ctrl->event, ret);
> + return 0;
> +}
> +
> +/**
> + * returns -1 on error, or size on success
> + */
> +static int do_send(struct libvchan *ctrl, const void *data, size_t size)
> +{
> + int real_idx = wr_prod(ctrl) & (wr_ring_size(ctrl) - 1);
> + int avail_contig = wr_ring_size(ctrl) - real_idx;
> + if (VCHAN_DEBUG) {
> + char metainfo[32];
> + struct iovec iov[2];
> + iov[0].iov_base = metainfo;
> + iov[0].iov_len = snprintf(metainfo, 32, "vchan wr %d/%d",
> ctrl->other_domain_id, ctrl->device_number);
> + iov[1].iov_base = (void *)data;
> + iov[1].iov_len = size;
> + writev(-1, iov, 2);
> + }
> + if (avail_contig > size)
> + avail_contig = size;
> + memcpy(wr_ring(ctrl) + real_idx, data, avail_contig);
> + if (avail_contig < size)
> + {
> + // we rolled across the end of the ring
> + memcpy(wr_ring(ctrl), data + avail_contig, size -
> avail_contig);
> + }
> + barrier(); // data must be in the ring prior to increment
> + wr_prod(ctrl) += size;
> + barrier(); // increment must happen prior to notify
> + if (send_notify(ctrl, VCHAN_NOTIFY_WRITE))
> + return -1;
> + return size;
> +}
> +
> +/**
> + * returns 0 if no buffer space is available, -1 on error, or size on success
> + */
> +int libvchan_send(struct libvchan *ctrl, const void *data, size_t size)
> +{
> + int avail;
> + while (1) {
> + if (!libvchan_is_open(ctrl))
> + return -1;
> + avail = fast_get_buffer_space(ctrl, size);
> + if (size <= avail)
> + return do_send(ctrl, data, size);
> + if (!ctrl->blocking)
> + return 0;
> + if (size > wr_ring_size(ctrl))
> + return -1;
> + if (libvchan_wait(ctrl))
> + return -1;
> + }
> +}
> +
> +int libvchan_write(struct libvchan *ctrl, const void *data, size_t size)
> +{
> + int avail;
> + if (!libvchan_is_open(ctrl))
> + return -1;
> + if (ctrl->blocking) {
> + size_t pos = 0;
> + while (1) {
> + avail = fast_get_buffer_space(ctrl, size - pos);
> + if (pos + avail > size)
> + avail = size - pos;
> + if (avail)
> + pos += do_send(ctrl, data + pos, avail);
> + if (pos == size)
> + return pos;
> + if (libvchan_wait(ctrl))
> + return -1;
> + if (!libvchan_is_open(ctrl))
> + return -1;
> + }
> + } else {
> + avail = fast_get_buffer_space(ctrl, size);
> + if (size > avail)
> + size = avail;
> + if (size == 0)
> + return 0;
> + return do_send(ctrl, data, size);
> + }
> +}
> +
> +static int do_recv(struct libvchan *ctrl, void *data, size_t size)
> +{
> + int real_idx = rd_cons(ctrl) & (rd_ring_size(ctrl) - 1);
> + int avail_contig = rd_ring_size(ctrl) - real_idx;
> + if (avail_contig > size)
> + avail_contig = size;
> + barrier(); // data read must happen after rd_cons read
> + memcpy(data, rd_ring(ctrl) + real_idx, avail_contig);
> + if (avail_contig < size)
> + {
> + // we rolled across the end of the ring
> + memcpy(data + avail_contig, rd_ring(ctrl), size -
> avail_contig);
> + }
> + rd_cons(ctrl) += size;
> + if (VCHAN_DEBUG) {
> + char metainfo[32];
> + struct iovec iov[2];
> + iov[0].iov_base = metainfo;
> + iov[0].iov_len = snprintf(metainfo, 32, "vchan rd %d/%d",
> ctrl->other_domain_id, ctrl->device_number);
> + iov[1].iov_base = data;
> + iov[1].iov_len = size;
> + writev(-1, iov, 2);
> + }
> + barrier(); // consumption must happen prior to notify of newly freed
> space
> + if (send_notify(ctrl, VCHAN_NOTIFY_READ))
> + return -1;
> + return size;
> +}
> +
> +/**
> + * reads exactly size bytes from the vchan.
> + * returns 0 if insufficient data is available, -1 on error, or size on
> success
> + */
> +int libvchan_recv(struct libvchan *ctrl, void *data, size_t size)
> +{
> + while (1) {
> + int avail = fast_get_data_ready(ctrl, size);
> + if (size <= avail)
> + return do_recv(ctrl, data, size);
> + if (!libvchan_is_open(ctrl))
> + return -1;
> + if (!ctrl->blocking)
> + return 0;
> + if (size > rd_ring_size(ctrl))
> + return -1;
> + if (libvchan_wait(ctrl))
> + return -1;
> + }
> +}
> +
> +int libvchan_read(struct libvchan *ctrl, void *data, size_t size)
> +{
> + while (1) {
> + int avail = fast_get_data_ready(ctrl, size);
> + if (avail && size > avail)
> + size = avail;
> + if (avail)
> + return do_recv(ctrl, data, size);
> + if (!libvchan_is_open(ctrl))
> + return -1;
> + if (!ctrl->blocking)
> + return 0;
> + if (libvchan_wait(ctrl))
> + return -1;
> + }
> +}
> +
> +int libvchan_is_open(struct libvchan* ctrl)
> +{
> + if (ctrl->is_server)
> + return ctrl->server_persist ? 1 : ctrl->ring->cli_live;
> + else
> + return ctrl->ring->srv_live;
> +}
> +
> +int libvchan_fd_for_select(struct libvchan *ctrl)
> +{
> + return xc_evtchn_fd(ctrl->event);
> +}
> +
> +void libvchan_close(struct libvchan *ctrl)
> +{
> + if (!ctrl)
> + return;
> + if (ctrl->read.order >= PAGE_SHIFT)
> + munmap(ctrl->read.buffer, 1 << ctrl->read.order);
> + if (ctrl->write.order >= PAGE_SHIFT)
> + munmap(ctrl->write.buffer, 1 << ctrl->write.order);
> + if (ctrl->ring) {
> + if (ctrl->is_server) {
> + ctrl->ring->srv_live = 0;
> + xc_gntshr_munmap(ctrl->gntshr, ctrl->ring, PAGE_SIZE);
> + } else {
> + ctrl->ring->cli_live = 0;
> + xc_gnttab_munmap(ctrl->gnttab, ctrl->ring, PAGE_SIZE);
> + }
> + }
> + if (ctrl->event) {
> + if (ctrl->event_port >= 0 && ctrl->ring)
> + xc_evtchn_notify(ctrl->event, ctrl->event_port);
> + xc_evtchn_close(ctrl->event);
> + }
> + if (ctrl->is_server) {
> + if (ctrl->gntshr)
> + xc_gntshr_close(ctrl->gntshr);
> + } else {
> + if (ctrl->gnttab)
> + xc_gnttab_close(ctrl->gnttab);
> + }
> + free(ctrl);
> +}
> diff --git a/tools/libvchan/libxenvchan.h b/tools/libvchan/libxenvchan.h
> new file mode 100644
> index 0000000..c4a3ab9
> --- /dev/null
> +++ b/tools/libvchan/libxenvchan.h
> @@ -0,0 +1,173 @@
> +/**
> + * @file
> + * @section AUTHORS
> + *
> + * Copyright (C) 2010 Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
> + *
> + * Authors:
> + * Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
> + * Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
> + *
> + * @section LICENSE
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> 02110-1301 USA
> + *
> + * @section DESCRIPTION
> + *
> + * Originally borrowed from the Qubes OS Project, http://www.qubes-os.org,
> + * this code has been substantially rewritten to use the gntdev and gntalloc
> + * devices instead of raw MFNs and map_foreign_range.
> + *
> + * This is a library for inter-domain communication. A standard Xen ring
> + * buffer is used, with a datagram-based interface built on top. The grant
> + * reference and event channels are shared in XenStore under the path
> + *
> /local/domain/<srv-id>/data/vchan/<cli-id>/<port>/{ring-ref,event-channel}
> + *
> + * The ring.h macros define an asymmetric interface to a shared data
> structure
> + * that assumes all rings reside in a single contiguous memory space. This
> is
> + * not suitable for vchan because the interface to the ring is symmetric
> except
> + * for the setup. Unlike the producer-consumer rings defined in ring.h, the
> + * size of the rings used in vchan are determined at execution time instead
> of
> + * compile time, so the macros in ring.h cannot be used to access the rings.
> + */
> +
> +#include <xen/io/libvchan.h>
> +#include <xen/sys/evtchn.h>
> +#include <xenctrl.h>
> +
> +struct libvchan_ring {
> + /* Pointer into the shared page. Offsets into buffer. */
> + struct ring_shared* shr;
> + /* ring data; may be its own shared page(s) depending on order */
> + void* buffer;
> + /**
> + * The size of the ring is (1 << order); offsets wrap around when they
> + * exceed this. This copy is required because we can't trust the order
> + * in the shared page to remain constant.
> + */
> + int order;
> +};
> +
> +/**
> + * struct libvchan: control structure passed to all library calls
> + */
> +struct libvchan {
> + /* person we communicate with */
> + int other_domain_id;
> + /* "port" we communicate on (allows multiple vchans to exist in
> xenstore) */
> + int device_number;
> + /* Mapping handle for shared ring page */
> + union {
> + xc_gntshr *gntshr; /* for server */
> + xc_gnttab *gnttab; /* for client */
> + };
> + /* Pointer to shared ring page */
> + struct vchan_interface *ring;
> + /* event channel interface */
> + xc_evtchn *event;
> + uint32_t event_port;
> + /* informative flags: are we acting as server? */
> + int is_server:1;
> + /* true if server remains active when client closes (allows
> reconnection) */
> + int server_persist:1;
> + /* true if operations should block instead of returning 0 */
> + int blocking:1;
> + /* communication rings */
> + struct libvchan_ring read, write;
> +};
> +
> +/**
> + * Set up a vchan, including granting pages
> + * @param logger Logger for libxc errors
> + * @param domain The peer domain that will be connecting
> + * @param devno A device number, used to identify this vchan in xenstore
> + * @param send_min The minimum size (in bytes) of the send ring (left)
> + * @param recv_min The minimum size (in bytes) of the receive ring (right)
> + * @return The structure, or NULL in case of an error
> + */
> +struct libvchan *libvchan_server_init(xentoollog_logger *logger, int domain,
> int devno, size_t read_min, size_t write_min);
> +/**
> + * Connect to an existing vchan. Note: you can reconnect to an existing vchan
> + * safely, however no locking is performed, so you must prevent multiple
> clients
> + * from connecting to a single server.
> + *
> + * @param logger Logger for libxc errors
> + * @param domain The peer domain to connect to
> + * @param devno A device number, used to identify this vchan in xenstore
> + * @return The structure, or NULL in case of an error
> + */
> +struct libvchan *libvchan_client_init(xentoollog_logger *logger, int domain,
> int devno);
> +/**
> + * Close a vchan. This deallocates the vchan and attempts to free its
> + * resources. The other side is notified of the close, but can still read any
> + * data pending prior to the close.
> + */
> +void libvchan_close(struct libvchan *ctrl);
> +
> +/**
> + * Packet-based receive: always reads exactly $size bytes.
> + * @param ctrl The vchan control structure
> + * @param data Buffer for data that was read
> + * @param size Size of the buffer and amount of data to read
> + * @return -1 on error, 0 if nonblocking and insufficient data is available,
> or $size
> + */
> +int libvchan_recv(struct libvchan *ctrl, void *data, size_t size);
> +/**
> + * Stream-based receive: reads as much data as possible.
> + * @param ctrl The vchan control structure
> + * @param data Buffer for data that was read
> + * @param size Size of the buffer
> + * @return -1 on error, otherwise the amount of data read (which may be zero
> if
> + * the vchan is nonblocking)
> + */
> +int libvchan_read(struct libvchan *ctrl, void *data, size_t size);
> +/**
> + * Packet-based send: send entire buffer if possible
> + * @param ctrl The vchan control structure
> + * @param data Buffer for data to send
> + * @param size Size of the buffer and amount of data to send
> + * @return -1 on error, 0 if nonblocking and insufficient space is
> available, or $size
> + */
> +int libvchan_send(struct libvchan *ctrl, const void *data, size_t size);
> +/**
> + * Stream-based send: send as much data as possible.
> + * @param ctrl The vchan control structure
> + * @param data Buffer for data to send
> + * @param size Size of the buffer
> + * @return -1 on error, otherwise the amount of data sent (which may be zero
> if
> + * the vchan is nonblocking)
> + */
> +int libvchan_write(struct libvchan *ctrl, const void *data, size_t size);
> +/**
> + * Waits for reads or writes to unblock, or for a close
> + */
> +int libvchan_wait(struct libvchan *ctrl);
> +/**
> + * Returns the event file descriptor for this vchan. When this FD is
> readable,
> + * libvchan_wait() will not block, and the state of the vchan has changed
> since
> + * the last invocation of libvchan_wait().
> + */
> +int libvchan_fd_for_select(struct libvchan *ctrl);
> +/**
> + * Query the state of the vchan shared page:
> + * return 0 when one side has called libvchan_close() or crashed
> + * return 1 when both sides are open
> + * return 2 [server only] when no client has yet connected
> + */
> +int libvchan_is_open(struct libvchan* ctrl);
> +/** Amount of data ready to read, in bytes */
> +int libvchan_data_ready(struct libvchan *ctrl);
> +/** Amount of data it is possible to send without blocking */
> +int libvchan_buffer_space(struct libvchan *ctrl);
> diff --git a/tools/libvchan/node-select.c b/tools/libvchan/node-select.c
> new file mode 100644
> index 0000000..ea1bfc6
> --- /dev/null
> +++ b/tools/libvchan/node-select.c
> @@ -0,0 +1,162 @@
> +/**
> + * @file
> + * @section AUTHORS
> + *
> + * Copyright (C) 2010 Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
> + *
> + * Authors:
> + * Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
> + * Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
> + *
> + * @section LICENSE
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this program; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> 02110-1301 USA
> + *
> + * @section DESCRIPTION
> + *
> + * This is a test program for libvchan. Communications are bidirectional,
> + * with either server (grant offeror) or client able to read and write.
> + */
> +
> +#include <stdlib.h>
> +#include <stdio.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <fcntl.h>
> +#include <errno.h>
> +
> +#include <libxenvchan.h>
> +
> +void usage(char** argv)
> +{
> + fprintf(stderr, "usage:\n"
> + "\t%s [client|server] domainid nodeid [rbufsiz wbufsiz]\n",
> + argv[0]);
> + exit(1);
> +}
> +
> +#define BUFSIZE 5000
> +char inbuf[BUFSIZE];
> +char outbuf[BUFSIZE];
> +int insiz = 0;
> +int outsiz = 0;
> +struct libvchan *ctrl = 0;
> +
> +void vchan_wr() {
> + if (!insiz)
> + return;
> + int ret = libvchan_write(ctrl, inbuf, insiz);
> + if (ret < 0) {
> + fprintf(stderr, "vchan write failed\n");
> + exit(1);
> + }
> + if (ret > 0) {
> + insiz -= ret;
> + memmove(inbuf, inbuf + ret, insiz);
> + }
> +}
> +
> +void stdout_wr() {
> + if (!outsiz)
> + return;
> + int ret = write(1, outbuf, outsiz);
> + if (ret < 0 && errno != EAGAIN)
> + exit(1);
> + if (ret > 0) {
> + outsiz -= ret;
> + memmove(outbuf, outbuf + ret, outsiz);
> + }
> +}
> +
> +/**
> + Simple libvchan application, both client and server.
> + Both sides may write and read, both from the libvchan and from
> + stdin/stdout (just like netcat).
> +*/
> +
> +int main(int argc, char **argv)
> +{
> + int ret;
> + int libvchan_fd;
> + if (argc < 4)
> + usage(argv);
> + if (!strcmp(argv[1], "server")) {
> + int rsiz = argc > 4 ? atoi(argv[4]) : 0;
> + int wsiz = argc > 5 ? atoi(argv[5]) : 0;
> + ctrl = libvchan_server_init(NULL, atoi(argv[2]),
> atoi(argv[3]), rsiz, wsiz);
> + } else if (!strcmp(argv[1], "client"))
> + ctrl = libvchan_client_init(NULL, atoi(argv[2]),
> atoi(argv[3]));
> + else
> + usage(argv);
> + if (!ctrl) {
> + perror("libvchan_*_init");
> + exit(1);
> + }
> +
> + fcntl(0, F_SETFL, O_NONBLOCK);
> + fcntl(1, F_SETFL, O_NONBLOCK);
> +
> + libvchan_fd = libvchan_fd_for_select(ctrl);
> + for (;;) {
> + fd_set rfds;
> + fd_set wfds;
> + FD_ZERO(&rfds);
> + FD_ZERO(&wfds);
> + if (insiz != BUFSIZE)
> + FD_SET(0, &rfds);
> + if (outsiz)
> + FD_SET(1, &wfds);
> + FD_SET(libvchan_fd, &rfds);
> + ret = select(libvchan_fd + 1, &rfds, &wfds, NULL, NULL);
> + if (ret < 0) {
> + perror("select");
> + exit(1);
> + }
> + if (FD_ISSET(0, &rfds)) {
> + ret = read(0, inbuf + insiz, BUFSIZE - insiz);
> + if (ret < 0 && errno != EAGAIN)
> + exit(1);
> + if (ret == 0) {
> + while (insiz) {
> + vchan_wr();
> + libvchan_wait(ctrl);
> + }
> + return 0;
> + }
> + if (ret)
> + insiz += ret;
> + vchan_wr();
> + }
> + if (FD_ISSET(libvchan_fd, &rfds)) {
> + libvchan_wait(ctrl);
> + vchan_wr();
> + }
> + if (FD_ISSET(1, &wfds))
> + stdout_wr();
> + while (libvchan_data_ready(ctrl) && outsiz < BUFSIZE) {
> + ret = libvchan_read(ctrl, outbuf + outsiz, BUFSIZE -
> outsiz);
> + if (ret < 0)
> + exit(1);
> + outsiz += ret;
> + stdout_wr();
> + }
> + if (!libvchan_is_open(ctrl)) {
> + fcntl(1, F_SETFL, 0);
> + while (outsiz)
> + stdout_wr();
> + return 0;
> + }
> + }
> +}
> diff --git a/tools/libvchan/node.c b/tools/libvchan/node.c
> new file mode 100644
> index 0000000..6a9204c
> --- /dev/null
> +++ b/tools/libvchan/node.c
> @@ -0,0 +1,169 @@
> +/**
> + * @file
> + * @section AUTHORS
> + *
> + * Copyright (C) 2010 Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
> + *
> + * Authors:
> + * Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
> + * Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
> + *
> + * @section LICENSE
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this program; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> 02110-1301 USA
> + *
> + * @section DESCRIPTION
> + *
> + * This is a test program for libvchan. Communications are in one direction,
> + * either server (grant offeror) to client or vice versa.
> + */
> +
> +#include <stdlib.h>
> +#include <stdio.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <time.h>
> +
> +#include <libxenvchan.h>
> +
> +int libvchan_write_all(struct libvchan *ctrl, char *buf, int size)
> +{
> + int written = 0;
> + int ret;
> + while (written < size) {
> + ret = libvchan_write(ctrl, buf + written, size - written);
> + if (ret <= 0) {
> + perror("write");
> + exit(1);
> + }
> + written += ret;
> + }
> + return size;
> +}
> +
> +int write_all(int fd, char *buf, int size)
> +{
> + int written = 0;
> + int ret;
> + while (written < size) {
> + ret = write(fd, buf + written, size - written);
> + if (ret <= 0) {
> + perror("write");
> + exit(1);
> + }
> + written += ret;
> + }
> + return size;
> +}
> +
> +void usage(char** argv)
> +{
> + fprintf(stderr, "usage:\n"
> + "%s [client|server] [read|write] domid nodeid\n", argv[0]);
> + exit(1);
> +}
> +
> +#define BUFSIZE 5000
> +char buf[BUFSIZE];
> +void reader(struct libvchan *ctrl)
> +{
> + int size;
> + for (;;) {
> + size = rand() % (BUFSIZE - 1) + 1;
> + size = libvchan_read(ctrl, buf, size);
> + fprintf(stderr, "#");
> + if (size < 0) {
> + perror("read vchan");
> + libvchan_close(ctrl);
> + exit(1);
> + }
> + size = write_all(1, buf, size);
> + if (size < 0) {
> + perror("stdout write");
> + exit(1);
> + }
> + if (size == 0) {
> + perror("write size=0?\n");
> + exit(1);
> + }
> + }
> +}
> +
> +void writer(struct libvchan *ctrl)
> +{
> + int size;
> + for (;;) {
> + size = rand() % (BUFSIZE - 1) + 1;
> + size = read(0, buf, size);
> + if (size < 0) {
> + perror("read stdin");
> + libvchan_close(ctrl);
> + exit(1);
> + }
> + if (size == 0)
> + break;
> + size = libvchan_write_all(ctrl, buf, size);
> + fprintf(stderr, "#");
> + if (size < 0) {
> + perror("vchan write");
> + exit(1);
> + }
> + if (size == 0) {
> + perror("write size=0?\n");
> + exit(1);
> + }
> + }
> +}
> +
> +
> +/**
> + Simple libvchan application, both client and server.
> + One side does writing, the other side does reading; both from
> + standard input/output fds.
> +*/
> +int main(int argc, char **argv)
> +{
> + int seed = time(0);
> + struct libvchan *ctrl = 0;
> + int wr = 0;
> + if (argc < 4)
> + usage(argv);
> + if (!strcmp(argv[2], "read"))
> + wr = 0;
> + else if (!strcmp(argv[2], "write"))
> + wr = 1;
> + else
> + usage(argv);
> + if (!strcmp(argv[1], "server"))
> + ctrl = libvchan_server_init(NULL, atoi(argv[3]),
> atoi(argv[4]), 0, 0);
> + else if (!strcmp(argv[1], "client"))
> + ctrl = libvchan_client_init(NULL, atoi(argv[3]),
> atoi(argv[4]));
> + else
> + usage(argv);
> + if (!ctrl) {
> + perror("libvchan_*_init");
> + exit(1);
> + }
> + ctrl->blocking = 1;
> +
> + srand(seed);
> + fprintf(stderr, "seed=%d\n", seed);
> + if (wr)
> + writer(ctrl);
> + else
> + reader(ctrl);
> + libvchan_close(ctrl);
> + return 0;
> +}
> diff --git a/xen/include/public/io/libvchan.h
> b/xen/include/public/io/libvchan.h
> new file mode 100644
> index 0000000..a3bf7cd
> --- /dev/null
> +++ b/xen/include/public/io/libvchan.h
> @@ -0,0 +1,97 @@
> +/**
> + * @file
> + * @section AUTHORS
> + *
> + * Copyright (C) 2010 Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
> + *
> + * Authors:
> + * Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
> + * Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
> + *
> + * @section LICENSE
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> 02110-1301 USA
> + *
> + * @section DESCRIPTION
> + *
> + * Originally borrowed from the Qubes OS Project, http://www.qubes-os.org,
> + * this code has been substantially rewritten to use the gntdev and gntalloc
> + * devices instead of raw MFNs and map_foreign_range.
> + *
> + * This is a library for inter-domain communication. A standard Xen ring
> + * buffer is used, with a datagram-based interface built on top. The grant
> + * reference and event channels are shared in XenStore under the path
> + *
> /local/domain/<srv-id>/data/vchan/<cli-id>/<port>/{ring-ref,event-channel}
> + *
> + * The ring.h macros define an asymmetric interface to a shared data
> structure
> + * that assumes all rings reside in a single contiguous memory space. This
> is
> + * not suitable for vchan because the interface to the ring is symmetric
> except
> + * for the setup. Unlike the producer-consumer rings defined in ring.h, the
> + * size of the rings used in vchan are determined at execution time instead
> of
> + * compile time, so the macros in ring.h cannot be used to access the rings.
> + */
> +
> +#include <stdint.h>
> +#include <sys/types.h>
> +
> +struct ring_shared {
> + uint32_t cons, prod;
> +};
> +
> +#define VCHAN_NOTIFY_WRITE 0x1
> +#define VCHAN_NOTIFY_READ 0x2
> +
> +/**
> + * vchan_interface: primary shared data structure
> + */
> +struct vchan_interface {
> + /**
> + * Standard consumer/producer interface, one pair per buffer
> + * left is client write, server read
> + * right is client read, server write
> + */
> + struct ring_shared left, right;
> + /**
> + * size of the rings, which determines their location
> + * 10 - at offset 1024 in ring's page
> + * 11 - at offset 2048 in ring's page
> + * 12+ - uses 2^(N-12) grants to describe the multi-page ring
> + * These should remain constant once the page is shared.
> + * Only one of the two orders can be 10 (or 11).
> + */
> + uint16_t left_order, right_order;
> + /**
> + * Shutdown detection:
> + * 0: client (or server) has exited
> + * 1: client (or server) is connected
> + * 2: client has not yet connected
> + */
> + uint8_t cli_live, srv_live;
> + /**
> + * Notification bits:
> + * VCHAN_NOTIFY_WRITE: send notify when data is written
> + * VCHAN_NOTIFY_READ: send notify when data is read (consumed)
> + * cli_notify is used for the client to inform the server of its
> action
> + */
> + uint8_t cli_notify, srv_notify;
> + /**
> + * Grant list: ordering is left, right. Must not extend into actual
> ring
> + * or grow beyond the end of the initial shared page.
> + * These should remain constant once the page is shared, to allow
> + * for possible remapping by a client that restarts.
> + */
> + uint32_t grants[0];
> +};
> +
> --
> 1.7.6.2
>
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