Re: [Qemu-devel] [PATCH 3/7] xen: add console backend driver.

[Anthony Liguori <anthony@codemonkey.ws>]

Gerd Hoffmann wrote:
> This patch adds a xenconsole backend driver.  It it based on current
> xen-unstable code.  It has been changed to make use of the common
> backend driver code.
>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  Makefile.target  |    1 +
>  hw/xen-backend.h |    3 +
>  hw/xen-console.c |  271 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  hw/xen-machine.c |    2 +
>  4 files changed, 277 insertions(+), 0 deletions(-)
>  create mode 100644 hw/xen-console.c
>
> diff --git a/Makefile.target b/Makefile.target
> index 0451048..05619fa 100644
> --- a/Makefile.target
> +++ b/Makefile.target
> @@ -517,6 +517,7 @@ endif
>  
>  # xen backend driver support
>  XEN_OBJS := xen-machine.o xen-backend.o
> +XEN_OBJS += xen-console.o
>  ifeq ($(CONFIG_XEN), yes)
>    OBJS += $(XEN_OBJS)
>    LIBS += $(XEN_LIBS)
> diff --git a/hw/xen-backend.h b/hw/xen-backend.h
> index db36ae7..55ffd31 100644
> --- a/hw/xen-backend.h
> +++ b/hw/xen-backend.h
> @@ -114,3 +114,6 @@ int xen_be_send_notify(struct xendev *xendev);
>  void xen_be_printf(struct xendev *xendev, int msg_level, const char *fmt, ...)
>      __attribute__ ((format(printf, 3, 4)));
>  
> +/* actual backend drivers */
> +struct devops xen_console_ops;      /* xen_console.c     */
> +
> diff --git a/hw/xen-console.c b/hw/xen-console.c
> new file mode 100644
> index 0000000..9c67f1b
> --- /dev/null
> +++ b/hw/xen-console.c
> @@ -0,0 +1,271 @@
> +/*
> + *  Copyright (C) International Business Machines  Corp., 2005
> + *  Author(s): Anthony Liguori <aliguori@us.ibm.com>
> + *
> + *  Copyright (C) Red Hat 2007
> + *
> + *  Xen Console
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; under version 2 of the License.
> + *
> + *  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 General Public License for more details.
> + *
> + *  You should have received a copy of the GNU General Public License
> + *  along with this program; if not, write to the Free Software
> + *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
> + */
> +
> +#include <malloc.h>
> +#include <stdlib.h>
> +#include <errno.h>
> +#include <string.h>
> +#include <sys/select.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <termios.h>
> +#include <stdarg.h>
> +#include <sys/mman.h>
> +#include <xs.h>
> +#include <xen/io/console.h>
> +#include <xenctrl.h>
> +
> +#include "hw.h"
> +#include "sysemu.h"
> +#include "qemu-char.h"
> +#include "xen-backend.h"
> +
> +#define dolog(val, fmt, ...) fprintf(stderr, fmt "\n", ## __VA_ARGS__)
> +
> +struct buffer {
> +    uint8_t *data;
> +    size_t consumed;
> +    size_t size;
> +    size_t capacity;
> +    size_t max_capacity;
> +};
> +
> +struct xen_console {
> +    struct xendev     xendev;  /* must be first */
> +    struct buffer     buffer;
> +    char              console[BUFSIZE];
> +    int               ring_ref;
> +    void              *sring;
> +    CharDriverState   *chr;
> +    int               backlog;
> +};
> +
> +static void buffer_append(struct xen_console *con)
> +{
> +    struct buffer *buffer = &con->buffer;
> +    XENCONS_RING_IDX cons, prod, size;
> +    struct xencons_interface *intf = con->sring;
> +
> +    cons = intf->out_cons;
> +    prod = intf->out_prod;
> +    xen_mb();
> +
> +    size = prod - cons;
> +    if ((size == 0) || (size > sizeof(intf->out)))
> +	return;
> +
> +    if ((buffer->capacity - buffer->size) < size) {
> +	buffer->capacity += (size + 1024);
> +	buffer->data = realloc(buffer->data, buffer->capacity);
> +	if (buffer->data == NULL) {
> +	    dolog(LOG_ERR, "Memory allocation failed");
> +	    exit(ENOMEM);
> +	}
> +    }
> +
> +    while (cons != prod)
> +	buffer->data[buffer->size++] = intf->out[
> +	    MASK_XENCONS_IDX(cons++, intf->out)];
> +
> +    xen_mb();
> +    intf->out_cons = cons;
> +    xen_be_send_notify(&con->xendev);
> +
> +    if (buffer->max_capacity &&
> +	buffer->size > buffer->max_capacity) {
> +	/* Discard the middle of the data. */
> +
> +	size_t over = buffer->size - buffer->max_capacity;
> +	uint8_t *maxpos = buffer->data + buffer->max_capacity;
> +
> +	memmove(maxpos - over, maxpos, over);
> +	buffer->data = realloc(buffer->data, buffer->max_capacity);
> +	buffer->size = buffer->capacity = buffer->max_capacity;
> +
> +	if (buffer->consumed > buffer->max_capacity - over)
> +	    buffer->consumed = buffer->max_capacity - over;
> +    }
> +}
> +
> +static void buffer_advance(struct buffer *buffer, size_t len)
> +{
> +    buffer->consumed += len;
> +    if (buffer->consumed == buffer->size) {
> +	buffer->consumed = 0;
> +	buffer->size = 0;
> +    }
> +}
> +
> +static int ring_free_bytes(struct xen_console *con)
> +{
> +    struct xencons_interface *intf = con->sring;
> +    XENCONS_RING_IDX cons, prod, space;
> +
> +    cons = intf->in_cons;
> +    prod = intf->in_prod;
> +    xen_mb();
> +
> +    space = prod - cons;
> +    if (space > sizeof(intf->in))
> +	return 0; /* ring is screwed: ignore it */
> +
> +    return (sizeof(intf->in) - space);
> +}
> +
> +static int xencons_can_receive(void *opaque)
> +{
> +    struct xen_console *con = opaque;
> +    return ring_free_bytes(con);
> +}
> +
> +static void xencons_receive(void *opaque, const uint8_t *buf, int len)
> +{
> +    struct xen_console *con = opaque;
> +    struct xencons_interface *intf = con->sring;
> +    XENCONS_RING_IDX prod;
> +    int i, max;
> +
> +    max = ring_free_bytes(con);
> +    /* The can_receive() func limits this, but check again anyway */
> +    if (max < len)
> +	len = max;
> +
> +    prod = intf->in_prod;
> +    for (i = 0; i < len; i++) {
> +	intf->in[MASK_XENCONS_IDX(prod++, intf->in)] =
> +	    buf[i];
> +    }
> +    xen_wmb();
> +    intf->in_prod = prod;
> +    xen_be_send_notify(&con->xendev);
> +}
> +
> +static void xencons_send(struct xen_console *con)
> +{
> +    ssize_t len, size;
> +
> +    size = con->buffer.size - con->buffer.consumed;
> +    len = qemu_chr_write(con->chr, con->buffer.data + con->buffer.consumed,
> +			 size);
> +    if (len < 1) {
> +	if (!con->backlog) {
> +	    con->backlog = 1;
> +	    xen_be_printf(&con->xendev, 1, "backlog piling up, nobody listening?\n");
> +	}
> +    } else {
> +	buffer_advance(&con->buffer, len);
> +	if (con->backlog && len == size) {
> +	    con->backlog = 0;
> +	    xen_be_printf(&con->xendev, 1, "backlog is gone\n");
> +	}
> +    }
> +}
> +
> +/* -------------------------------------------------------------------- */
> +
> +static int con_init(struct xendev *xendev)
> +{
> +    struct xen_console *con = container_of(xendev, struct xen_console, xendev);
> +    char *type;
> +
> +    if (!serial_hds[con->xendev.dev]) {
> +	xen_be_printf(xendev, 1, "serial line %d not configured\n", con->xendev.dev);
> +	return -1;
> +    }
> +
> +    /* setup */
> +    snprintf(con->console, sizeof(con->console),
> +	     "/local/domain/%d/console", con->xendev.dom);
> +    con->chr = serial_hds[con->xendev.dev];
> +
> +    type = xenstore_read_str(con->console, "type");
> +    if (!type || 0 != strcmp(type, "ioemu")) {
> +	xen_be_printf(xendev, 1, "not for me (type=%s)\n", type);
> +	return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +static int con_connect(struct xendev *xendev)
> +{
> +    struct xen_console *con = container_of(xendev, struct xen_console, xendev);
> +    int limit;
> +
> +    if (-1 == xenstore_read_int(con->console, "ring-ref", &con->ring_ref))
> +	return -1;
> +    if (-1 == xenstore_read_int(con->console, "port", &con->xendev.remote_port))
> +	return -1;
> +    if (0 == xenstore_read_int(con->console, "limit", &limit))
> +	con->buffer.max_capacity = limit;
> +
> +    con->sring = xc_map_foreign_range(xen_xc, con->xendev.dom,
> +				      XC_PAGE_SIZE,
> +				      PROT_READ|PROT_WRITE,
> +				      con->ring_ref);
> +    if (!con->sring)
> +	return -1;
> +
> +    xen_be_bind_evtchn(&con->xendev);
> +    qemu_chr_add_handlers(con->chr, xencons_can_receive, xencons_receive,
> +			  NULL, con);
> +
> +    xen_be_printf(xendev, 1, "ring mfn %d, remote port %d, local port %d, limit %zd\n",
> +		  con->ring_ref,
> +		  con->xendev.remote_port,
> +		  con->xendev.local_port,
> +		  con->buffer.max_capacity);
> +    return 0;
> +}
> +
> +static void con_disconnect(struct xendev *xendev)
> +{
> +    struct xen_console *con = container_of(xendev, struct xen_console, xendev);
> +
> +    qemu_chr_add_handlers(con->chr, NULL, NULL, NULL, NULL);
> +    xen_be_unbind_evtchn(&con->xendev);
> +
> +    if (con->sring) {
> +	munmap(con->sring, XC_PAGE_SIZE);
> +	con->sring = NULL;
> +    }
> +}
> +
> +static void con_event(struct xendev *xendev)
> +{
> +    struct xen_console *con = container_of(xendev, struct xen_console, xendev);
> +
> +    buffer_append(con);
> +    if (con->buffer.size - con->buffer.consumed)
> +	xencons_send(con);
> +}
> +
> +/* -------------------------------------------------------------------- */
> +
> +struct devops xen_console_ops = {
>   

I missed it in the previous patchset, but it would be nice to QEMU-ify 
these things.  For instance, 'struct xen_console' => 'XenConsole', 
'struct devopts' => 'XenDevOpts', etc.

Regards,

Anthony Liguori

> +    .size       = sizeof(struct xen_console),
> +    .flags      = DEVOPS_FLAG_IGNORE_STATE,
> +    .init       = con_init,
> +    .connect    = con_connect,
> +    .event      = con_event,
> +    .disconnect = con_disconnect,
> +};
> diff --git a/hw/xen-machine.c b/hw/xen-machine.c
> index 798c0a7..da10982 100644
> --- a/hw/xen-machine.c
> +++ b/hw/xen-machine.c
> @@ -57,6 +57,8 @@ static void xenpv_init(ram_addr_t ram_size, int vga_ram_size,
>  
>      /* setup xen backend handlers */
>      xen_be_init();
> +
> +    xen_be_register("console", &xen_console_ops);
>  }
>  
>  QEMUMachine xenpv_machine = {
>