Re: [Qemu-devel] [PATCH V2] Support logging xen-guest console

[Anthony Liguori]

On 06/22/2011 02:26 AM, Chunyan Liu wrote:
> Add code to support logging xen-domU console, as what xenconsoled does. Log info
> will be saved in /var/log/xen/console/guest-domUname.log.

It needs to be specified by command line.  It's not appropriate to 
assume qemu is running as root with access to a non-user directory.

Regards,

Anthony Liguori

> Signed-off-by: Chunyan Liu<address@hidden>
> ---
>   hw/xen_console.c |   71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>   1 files changed, 71 insertions(+), 0 deletions(-)
>
> diff --git a/hw/xen_console.c b/hw/xen_console.c
> index c6c8163..f898e4f 100644
> --- a/hw/xen_console.c
> +++ b/hw/xen_console.c
> @@ -36,6 +36,8 @@
>   #include "qemu-char.h"
>   #include "xen_backend.h"
>
> +static int log_guest = 0;
> +
>   struct buffer {
>       uint8_t *data;
>       size_t consumed;
> @@ -52,8 +54,24 @@ struct XenConsole {
>       void              *sring;
>       CharDriverState   *chr;
>       int               backlog;
> +    int               log_fd;
>   };
>
> +static int write_all(int fd, const char* buf, size_t len)
> +{
> +    while (len) {
> +        ssize_t ret = write(fd, buf, len);
> +        if (ret == -1&&  errno == EINTR)
> +            continue;
> +        if (ret<  0)
> +            return -1;
> +        len -= ret;
> +        buf += ret;
> +    }
> +
> +    return 0;
> +}
> +
>   static void buffer_append(struct XenConsole *con)
>   {
>       struct buffer *buffer =&con->buffer;
> @@ -81,6 +99,15 @@ static void buffer_append(struct XenConsole *con)
>       intf->out_cons = cons;
>       xen_be_send_notify(&con->xendev);
>
> +    if (con->log_fd != -1) {
> +        int logret;
> +        logret = write_all(con->log_fd, buffer->data + buffer->size - size, 
> size);
> +        if (logret<  0) {
> +            xen_be_printf(&con->xendev, 1, "Write to log failed on domain %d: %d 
> (%s)\n",
> +                      con->xendev.dom, errno, strerror(errno));
> +        }
> +     }
> +
>       if (buffer->max_capacity&&
>         buffer->size>  buffer->max_capacity) {
>         /* Discard the middle of the data. */
> @@ -174,12 +201,43 @@ static void xencons_send(struct XenConsole *con)
>       }
>   }
>
> +static int create_domain_log(struct XenConsole *con)
> +{
> +    char *logfile;
> +    char *path, *domname;
> +    int fd;
> +    const char *logdir = "/var/log/xen/console";
> +
> +    path = xs_get_domain_path(xenstore, con->xendev.dom);
> +    domname = xenstore_read_str(path, "name");
> +    free(path);
> +    if (!domname)
> +        return -1;
> +
> +    if (mkdir(logdir, 0755)&&  errno != EEXIST)
> +    {
> +        xen_be_printf(&con->xendev, 1,  "Directory %s does not exist and fail to 
> create it!", logdir);
> +        return -1;
> +    }
> +
> +    asprintf(&logfile, "%s/guest-%s.log", logdir, domname);
> +    qemu_free(domname);
> +
> +    fd = open(logfile, O_WRONLY|O_CREAT|O_APPEND, 0644);
> +    free(logfile);
> +    if (fd == -1)
> +        xen_be_printf(&con->xendev, 1,  "Failed to open log %s: %d (%s)", 
> logfile, errno, strerror(errno));
> +
> +    return fd;
> +}
> +
>   /* -------------------------------------------------------------------- */
>
>   static int con_init(struct XenDevice *xendev)
>   {
>       struct XenConsole *con = container_of(xendev, struct XenConsole, xendev);
>       char *type, *dom;
> +    char *logenv = NULL;
>
>       /* setup */
>       dom = xs_get_domain_path(xenstore, con->xendev.dom);
> @@ -198,6 +256,10 @@ static int con_init(struct XenDevice *xendev)
>       else
>           con->chr = serial_hds[con->xendev.dev];
>
> +    logenv = getenv("XENCONSOLED_TRACE");
> +    if (logenv != NULL&&  strlen(logenv) == strlen("guest")&&  !strcmp(logenv, 
> "guest")) {
> +        log_guest = 1;
> +    }
>       return 0;
>   }
>
> @@ -230,6 +292,9 @@ static int con_connect(struct XenDevice *xendev)
>                   con->xendev.remote_port,
>                   con->xendev.local_port,
>                   con->buffer.max_capacity);
> +    con->log_fd = -1;
> +    if (log_guest)
> +         con->log_fd = create_domain_log(con);
>       return 0;
>   }
>
> @@ -245,6 +310,12 @@ static void con_disconnect(struct XenDevice *xendev)
>         munmap(con->sring, XC_PAGE_SIZE);
>         con->sring = NULL;
>       }
> +
> +    if (con->log_fd != -1) {
> +        close(con->log_fd);
> +        con->log_fd = -1;
> +    }
> +
>   }
>
>   static void con_event(struct XenDevice *xendev)