Re: [Qemu-devel] [PATCH v3 0/6] qemu: guest agent: implement guest-exec command

["Denis V. Lunev" <den@openvz.org>]

On 21/05/15 08:49, Denis V. Lunev wrote:
> These patches for guest-agent add the functionality to execute commands on
> a guest UNIX machine.
>
> These patches add the following interfaces:
>
> guest-pipe-open
> guest-exec
> guest-exec-status
>
> With these interfaces it's possible to:
>
> * Open an anonymous pipe and work with it as with a file using already
> implemented interfaces guest-file-{read,write,flush,close}.
>
> * Execute a binary or a script on a guest machine.
> We can pass arbitrary arguments and environment to a new child process.
>
> * Pass redirected IO from/to stdin, stdout, stderr from a child process to a
> local file or an anonymous pipe.
>
> * Check the status of a child process, get its exit status if it exited or get
> signal number if it was killed.
>
> We plan to add support for Windows in the near future using the same interfaces
> we introduce here.
>
> Example of usage:
>
> {"execute": "guest-pipe-open", "arguments":{"mode": "r"}}
> {'return': 1000}
>
> {"execute":"guest-exec", "arguments":{ "path": "id", "params": ["user"],
>      "env": ["MYENV=myvalue"], "handle_stdout": 1000 }}'
> {"return": 2636}
>
> {"execute": "guest-exec-status", "arguments": {"pid": 2636}}
> {"return":{"exit":0,"handle_stderr":-1,"handle_stdin":-1,"handle_stdout":1000,"signal":-1}}
>
> {"execute": "guest-file-read", "arguments": {"handle": 1000, "count":128}}
> {"return":{"count":58,"buf-b64":"dWlk...","eof":true}}
>
> {"execute": "guest-file-close", "arguments": {"handle": 1000}}
> {"return":{}}
>
>
> These patches are based on the patches proposed by Michael Roth in 2011:
> http://lists.gnu.org/archive/html/qemu-devel/2011-12/msg00722.html
>
> We made several modifications to the interfaces proposed by Michael to simplify
> their usage and we also added several new functions:
>
> * Arguments to an executable file are passed as an array of strings.
>
>      Before that we had to pass parameters like this:
>      'params': [ {'param': '-b'}, {'param': '-n1'} ]
>
>      Now we may pass them just as an array of strings:
>      'params': [ '-b', '-n1' ]
>
> * Environment can be passed to a child process.
>
>      "env": ["MYENV=myvalue"]
>
> * Removed "detach" argument from "guest-exec" - it never waits for a child
> process to signal.  With this change it's possible to return just PID from
> "guest-exec", a user must call "guest-exec-status" to get the status of a child.
>
> * Removed "wait" argument from "guest-exec-status" - waiting for a child process
> to signal is dangerous, because it may block the whole qemu-ga.  Instead, the
> command polls just once a status of a child.
>
> * "guest-exec-status" returns exit status of a child process or a signal number,
> in case a process was killed.
>
> * Simplified the command "guest-pipe-open" - the way how it stores the pipe
> fd's.  No additional logic is needed about which end of pipe should be closed
> with "guest-file-close".  This way we avoid modifying the interface of the
> existing "guest-file-close".
>
> In the conversation about the original patches there was a suggestion to merge
> "path" and "params" into one single list.  But we didn't do so, because having
> separate "path" is similar to exec*() family functions in UNIX.  That way it
> looks more consistent.
>
> Changes from v2:
> - return code of commands changed to dictionary
> - ported to current HEAD
> - new way for moving pipe to non-blocking state (universal)
>
> Changes from v1:
> - Windows version of the patchset is added
> - SIGPIPE processing is added for Unix version of the patchset
> - added guest_exec_file_busy() to prevent GuestFileHandle* object from being
>    deleted in case it's used in guest-exec command.
>
> Signed-off-by: Olga Krishtal <okrishtal@parallels.com>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
>
> P.S. Michael, this is a working version and could we consider it for merging
>       into 2.4? If you still want to use universal GLIB code, we could
>       re-write this later using standard refactoring way.
>
PING, 1 week till soft freeze.

Eric, Michael, can you pls consider these patches? We have
really small amount of time left.

Regards,
     Den