Re: [Qemu-devel] [PATCH 2/3] QAPI: Introduce memchar-write QMP command

[Luiz Capitulino]

On Tue, 22 Jan 2013 16:12:51 +0800
Lei Li <address@hidden> wrote:

> Signed-off-by: Lei Li <address@hidden>
> ---
>  hmp-commands.hx  |   16 ++++++++++++++++
>  hmp.c            |   13 +++++++++++++
>  hmp.h            |    1 +
>  qapi-schema.json |   41 +++++++++++++++++++++++++++++++++++++++++
>  qemu-char.c      |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
>  qmp-commands.hx  |   34 ++++++++++++++++++++++++++++++++++
>  6 files changed, 153 insertions(+), 0 deletions(-)
> 
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index 0934b9b..e546c76 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -837,6 +837,22 @@ STEXI
>  @item nmi @var{cpu}
>  @findex nmi
>  Inject an NMI on the given CPU (x86 only).
> +
> +ETEXI
> +
> +    {
> +        .name       = "memchar_write",
> +        .args_type  = "chardev:s,data:s",
> +        .params     = "chardev data",

This is missing .help. Please look at the other entries for examples.

> +        .mhandler.cmd = hmp_memchar_write,
> +    },
> +
> +STEXI
> address@hidden memchar_write @var{chardev} @var{data}
> address@hidden memchar_write
> +Provide writing interface for CirMemCharDriver. Write @var{data}
> +to char device 'memory'.
> +
>  ETEXI
>  
>      {
> diff --git a/hmp.c b/hmp.c
> index c7b6ba0..546d687 100644
> --- a/hmp.c
> +++ b/hmp.c
> @@ -684,6 +684,19 @@ void hmp_pmemsave(Monitor *mon, const QDict *qdict)
>      hmp_handle_error(mon, &errp);
>  }
>  
> +void hmp_memchar_write(Monitor *mon, const QDict *qdict)
> +{
> +    uint32_t size;
> +    const char *chardev = qdict_get_str(qdict, "chardev");
> +    const char *data = qdict_get_str(qdict, "data");
> +    Error *errp = NULL;
> +
> +    size = strlen(data);
> +    qmp_memchar_write(chardev, size, data, false, 0, &errp);
> +
> +    hmp_handle_error(mon, &errp);
> +}
> +
>  static void hmp_cont_cb(void *opaque, int err)
>  {
>      if (!err) {
> diff --git a/hmp.h b/hmp.h
> index 44be683..06d6ea2 100644
> --- a/hmp.h
> +++ b/hmp.h
> @@ -43,6 +43,7 @@ void hmp_system_powerdown(Monitor *mon, const QDict *qdict);
>  void hmp_cpu(Monitor *mon, const QDict *qdict);
>  void hmp_memsave(Monitor *mon, const QDict *qdict);
>  void hmp_pmemsave(Monitor *mon, const QDict *qdict);
> +void hmp_memchar_write(Monitor *mon, const QDict *qdict);
>  void hmp_cont(Monitor *mon, const QDict *qdict);
>  void hmp_system_wakeup(Monitor *mon, const QDict *qdict);
>  void hmp_inject_nmi(Monitor *mon, const QDict *qdict);
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 6d7252b..c34e9ac 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -325,6 +325,47 @@
>  { 'command': 'query-chardev', 'returns': ['ChardevInfo'] }
>  
>  ##
> +# @DataFormat:
> +#
> +# An enumeration of data format.
> +#
> +# @utf8: The data format is 'utf8'.
> +#
> +# @base64: The data format is 'base64'.
> +#
> +# Since: 1.4
> +##
> +{ 'enum': 'DataFormat'
> +  'data': [ 'utf8', 'base64' ] }
> +
> +##
> +# @memchar-write:
> +#
> +# Provide writing interface for memchardev. Write data to char
> +# device 'memory'.
> +#
> +# @chardev: the name of the memory char device.

I wonder if this should be 'device' instead.

> +#
> +# @size: the size to write in bytes.
> +#
> +# @data: the source data write to memchar.
> +#
> +# @format: #optional the format of the data write to chardev 'memory',
> +#          by default is 'utf8'.
> +#
> +# Returns: Nothing on success
> +#          If @chardev is not a valid char device, DeviceNotFound
> +#
> +# Notes: For now assume 'drop' behaver, which would result in writes
> +#        dropping queued data.

I agree this is the desired interface, but it's not what it does, see
below.

> +#
> +# Since: 1.4
> +##
> +{ 'command': 'memchar-write',
> +  'data': {'chardev': 'str', 'size': 'int', 'data': 'str',
> +           '*format': 'DataFormat'} }
> +
> +##
>  # @CommandInfo:
>  #
>  # Information about a QMP command
> diff --git a/qemu-char.c b/qemu-char.c
> index b323e94..c3bb6ec 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -2754,6 +2754,54 @@ fail:
>      return NULL;
>  }
>  
> +static bool qemu_is_chr(const CharDriverState *chr, const char *filename)
> +{
> +    return strcmp(chr->filename, filename);
> +}
> +
> +void qmp_memchar_write(const char *chardev, int64_t size,
> +                       const char *data, bool has_format,
> +                       enum DataFormat format,
> +                       Error **errp)
> +{
> +    CharDriverState *chr;
> +    guchar *write_data;
> +    int ret;
> +    gsize write_count;
> +
> +    chr = qemu_chr_find(chardev);
> +    if (!chr) {
> +        error_set(errp, QERR_DEVICE_NOT_FOUND, chardev);
> +        return;
> +    }
> +
> +    if (qemu_is_chr(chr, "memory")) {
> +        error_setg(errp,"%s is not memory char device\n", chardev);

Please, drop the trailing '\n'.

> +        return;
> +    }
> +
> +    /* XXX: Drop the coming data when the buffer is full. */
> +    if (cirmem_chr_is_full(chr)) {
> +        error_setg(errp, "Memory device %s is full", chardev);
> +        return;
> +    }

This is where the code contradicts the doc, and we can't fix this
later because we'd change the interface.

Why can't you just drop this check?

> +
> +    write_count = (gsize)size;
> +
> +    if (has_format && (format == DATA_FORMAT_BASE64)) {
> +        write_data = g_base64_decode(data, &write_count);
> +    } else {
> +        write_data = (uint8_t *)data;
> +    }
> +
> +    ret = cirmem_chr_write(chr, write_data, write_count);
> +
> +    if (ret < 0) {
> +        error_setg(errp, "Failed to write to device %s", chardev);
> +        return;
> +    }
> +}
> +
>  QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename)
>  {
>      char host[65], port[33], width[8], height[8];
> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index cbf1280..8ad06d0 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -466,6 +466,40 @@ Note: inject-nmi fails when the guest doesn't support 
> injecting.
>  EQMP
>  
>      {
> +        .name       = "memchar-write",
> +        .args_type  = "chardev:s,size:i,data:s,format:s?",
> +        .help       = "write size of data to memory chardev",

Please, drop .help. We only use it for hmp commands.

> +        .mhandler.cmd_new = qmp_marshal_input_memchar_write,
> +    },
> +
> +SQMP
> +memchar-write
> +-------------
> +
> +Provide writing interface for CirMemCharDriver. Write data to memory
> +char device.
> +
> +Arguments:
> +
> +- "chardev": the name of the char device, must be unique (json-string)
> +- "size": the memory size, in bytes, should be power of 2 (json-int)
> +- "data": the source data write to memory (json-string)
> +- "format": the data format write to memory, default is
> +            utf8. (json-string, optional)
> +          - Possible values: "utf8", "base64"
> +
> +Example:
> +
> +-> { "execute": "memchar-write",
> +                "arguments": { "chardev": foo,
> +                               "size": 8,
> +                               "data": "abcdefgh",
> +                               "format": "utf8" } }
> +<- { "return": {} }
> +
> +EQMP
> +
> +    {
>          .name       = "xen-save-devices-state",
>          .args_type  = "filename:F",
>      .mhandler.cmd_new = qmp_marshal_input_xen_save_devices_state,