Re: [Qemu-devel] [PATCH 2/4] QAPI: Introduce memchar-write QMP command

[Lei Li <lilei@linux.vnet.ibm.com>]

On 10/29/2012 09:23 PM, Luiz Capitulino wrote:
> On Mon, 29 Oct 2012 12:10:24 +0800
> Lei Li <lilei@linux.vnet.ibm.com> wrote:
>
>> On 10/27/2012 01:17 AM, Luiz Capitulino wrote:
>>> On Fri, 26 Oct 2012 19:21:50 +0800
>>> Lei Li <lilei@linux.vnet.ibm.com> wrote:
>>>
>>>> Signed-off-by: Lei Li <lilei@linux.vnet.ibm.com>
>>>> ---
>>>>    hmp-commands.hx  |   17 +++++++++++++++++
>>>>    hmp.c            |   15 +++++++++++++++
>>>>    hmp.h            |    1 +
>>>>    qapi-schema.json |   47 +++++++++++++++++++++++++++++++++++++++++++++++
>>>>    qemu-char.c      |   44 ++++++++++++++++++++++++++++++++++++++++++++
>>>>    qmp-commands.hx  |   34 ++++++++++++++++++++++++++++++++++
>>>>    6 files changed, 158 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/hmp-commands.hx b/hmp-commands.hx
>>>> index e0b537d..a37b8e9 100644
>>>> --- a/hmp-commands.hx
>>>> +++ b/hmp-commands.hx
>>>> @@ -825,6 +825,23 @@ Inject an NMI on the given CPU (x86 only).
>>>>    ETEXI
>>>>    
>>>>        {
>>>> +        .name       = "memchar_write",
>>>> +        .args_type  = "chardev:s,data:s",
>>>> +        .params     = "chardev data",
>>>> +        .mhandler.cmd = hmp_memchar_write,
>>>> +    },
>>>> +
>>>> +STEXI
>>>> +@item memchar_write @var{chardev} @var{data}
>>>> +@findex memchar_write
>>>> +Provide writing interface for CirMemCharDriver. Write @var{data}
>>>> +to cirmemchr char device. Note that we  will add 'control' options
>>>> +for read and write command that specifies behavior when the queue
>>>> +is full/empty, for now just assume a drop behaver in these two commands.
>>> You can drop everything after "Note".
>>>
>> ok
>>
>>>> +
>>>> +ETEXI
>>>> +
>>>> +    {
>>>>            .name       = "migrate",
>>>>            .args_type  = "detach:-d,blk:-b,inc:-i,uri:s",
>>>>            .params     = "[-d] [-b] [-i] uri",
>>>> diff --git a/hmp.c b/hmp.c
>>>> index 2b97982..082985b 100644
>>>> --- a/hmp.c
>>>> +++ b/hmp.c
>>>> @@ -683,6 +683,21 @@ 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");
>>>> +    enum DataFormat format;
>>> Why do you need this variable?
>> Sure, I will drop this.
>>
>>>> +    Error *errp = NULL;
>>>> +
>>>> +    size = strlen(data);
>>>> +    format = DATA_FORMAT_UTF8;
>>>> +    qmp_memchar_write(chardev, size, data, true, format, &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 71ea384..406ebb1 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 c615ee2..43ef6bc 100644
>>>> --- a/qapi-schema.json
>>>> +++ b/qapi-schema.json
>>>> @@ -325,6 +325,53 @@
>>>>    { 'command': 'query-chardev', 'returns': ['ChardevInfo'] }
>>>>    
>>>>    ##
>>>> +# @DataFormat:
>>>> +#
>>>> +# An enumeration of data format. The default value would
>>>> +# be utf8.
>>> Please, remove the "default value" part. This is decided by the command
>>> using this type.
>> Now the option format is optional, if it's not set then default by 'utf8'.
>> I think it's a reasonable behaver. :)
> What I meant is that the right place to say what the value is is in
> the command documentation, not in @DataFormat doc. Here, only having
> "An enumeration of data encodings" is fine.

OK, done.

>>>> +#
>>>> +# @utf8: The data format is 'utf8'.
>>>> +#
>>>> +# @base64: The data format is 'base64'.
>>>> +#
>>>> +# Note: The data format start with 'utf8' and 'base64',
>>>> +#       will support other data format as well.
>>> Please, drop this note. It's not needed.
>>>
>> ok
>>
>>>> +#
>>>> +# Since: 1.3
>>>> +##
>>>> +{ 'enum': 'DataFormat'
>>>> +  'data': [ 'utf8', 'base64' ] }
>>>> +
>>>> +##
>>>> +# @memchar-write:
>>>> +#
>>>> +# Provide writing interface for memchardev. Write data to memchar
>>>> +# char device.
>>>> +#
>>>> +# @chardev: the name of the memchar char device.
>>>> +#
>>>> +# @size: the size to write in bytes. Should be power of 2.
>>>> +#
>>>> +# @data: the source data write to memchar.
>>>> +#
>>>> +# @format: #optional the format of the data write to memchardev, by
>>>> +#          default is 'utf8'.
>>>> +#
>>>> +# Returns: Nothing on success
>>>> +#          If @chardev is not a valid memchr device, DeviceNotFound
>>>> +#
>>>> +# Notes: The option 'block' is not supported now due to the miss
>>>> +#        feature in qmp. Will add it later when we gain the necessary
>>>> +#        infrastructure enhancement. For now just assume 'drop' behaver
>>>> +#        for this command.
>>> Please, replace this note with an explanation of the current behavior. No
>>> need to talk about the future.
>> Sure.
>>
>>>> +#
>>>> +# Since: 1.3
>>>> +##
>>>> +{ '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 c3ec43d..6114e29 100644
>>>> --- a/qemu-char.c
>>>> +++ b/qemu-char.c
>>>> @@ -2717,6 +2717,50 @@ fail:
>>>>        return NULL;
>>>>    }
>>>>    
>>>> +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 (strcmp(chr->filename, "memchr") != 0) {
>>>> +        error_setg(errp,"%s is not memory char device\n", chardev);
>>>> +        return;
>>>> +    }
>>> This is wrong, as it's unreliable. A hackish (but hopefully correct) way
>>> of doing this would be to check chr->init against the circmem init function.
>>> But please, put this behind a function because it's ugly.
>> Hmm, I guess it's because the chr->filename could be NULL. but we can still
>> get it since CharDriverState keeps the inited type of backend. I am not sure
>> that check chr->init against the cirmem init funciton could work, I'll have
>> a try.
>>
>>>> +
>>>> +    /* XXX: For the sync command as 'block', waiting for the qmp
>>>> +     * to support necessary feature. Now just act as 'drop' */
>>> Please, replace this note with an explanation of the current behavior.
>> ok.
>>
>>>> +    if (cirmem_chr_is_full(chr)) {
>>>> +        error_setg(errp, "Failed to write to memchr %s", chardev);
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    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);
>>> IIRC circmem_chr_write() doesn't check if write_count if a power of two,
>>> what happens if it isn't?
>> I have considered your suggestion on this in v4. The reason why I did not
>> add the assert is that I think we have already check with this when cirmem
>> init, so there is no need to check it again. Correct me if I am wrong. :)
> I was actually asking an honest question: does cirmem_chr_write() assume
> that len is a power of two? If yes, what if the user doesn't pass a
> power of two value to qmp_memchar_write()?

Ah, there must be some misunderstanding here... :) We let the size of ring
buffer inited as power of 2, not the write_count. And it has already been
checked when we init the CirMemCharDriver. That's why I did not
add the assert in the function cirmem_chr_write.

>
>>>> +
>>>> +    if (ret < 0) {
>>>> +        error_setg(errp, "Failed to write to memchr %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 5ba8c48..7548b9b 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?,control:s?",
>>> You've dropped 'control', haven't you?
>> Yes, sorry I forgot to drop here.. :(
>>
>>>> +        .help       = "write size of data to memchar chardev",
>>>> +        .mhandler.cmd_new = qmp_marshal_input_memchar_write,
>>>> +    },
>>>> +
>>>> +SQMP
>>>> +memchar-write
>>>> +-------------
>>>> +
>>>> +Provide writing interface for memchardev. Write data to memchar
>>>> +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 writed to memchar (json-string)
>>>> +- "format": the data format write to memchardev, 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,
>>


-- 
Lei