[PATCH v2] libxl: add "xl qemu-monitor-command"

[PATCH v2] libxl: add "xl qemu-monitor-command"

[Juergen Gross]

Add a new xl command "qemu-monitor-command" to issue arbitrary commands
to a domain's device model. Syntax is:

xl qemu-monitor-command <domain> <command>

The command is issued via qmp human-monitor-command command. Any
information returned by the command is printed to stdout.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 docs/man/xl.pod.1.in           | 36 ++++++++++++++++++++++++++++++++++++
 tools/libxl/libxl.h            | 14 ++++++++++++++
 tools/libxl/libxl_colo_qdisk.c |  2 +-
 tools/libxl/libxl_internal.h   |  3 ++-
 tools/libxl/libxl_qmp.c        | 38 ++++++++++++++++++++++++++++++++++++--
 tools/libxl/xl.h               |  1 +
 tools/libxl/xl_cmdimpl.c       | 27 +++++++++++++++++++++++++++
 tools/libxl/xl_cmdtable.c      |  5 +++++
 8 files changed, 122 insertions(+), 4 deletions(-)

diff --git a/docs/man/xl.pod.1.in b/docs/man/xl.pod.1.in
index 1adf322..a2be541 100644
--- a/docs/man/xl.pod.1.in
+++ b/docs/man/xl.pod.1.in
@@ -1516,6 +1516,42 @@ List pass-through usb devices for a domain.
 
 =back
 
+=head1 DEVICE-MODEL CONTROL
+
+=over 4
+
+=item B<qemu-monitor-command> I<domain-id> I<command>
+
+Issue a monitor command to the device model of the domain specified by
+I<domain-id>. I<command> can be any valid command qemu understands. This
+can be e.g. used to add non-standard devices or devices with non-standard
+parameters to a domain. The output of the command is printed to stdout.
+
+B<Warning:> This qemu monitor access is provided for convenience when
+debugging, troubleshooting, and experimenting.  Its use is not
+supported by the Xen Project.
+
+Specifically, not all information printed by the qemu monitor will
+necessarily be accurate or complete, because in a Xen system qemu
+does not have a complete view of the guest.
+
+Furthermore, modifying the guest's setup via the qemu monitor may
+conflict with the Xen toolstack's assumptions.  Resulting problems
+may include, but are not limited to: guest crashes; toolstack error
+messages; inability to migrate the guest; and security
+vulnerabilities which are not covered by the Xen Project security
+response policy.
+
+B<EXAMPLE>
+
+Obtain information of USB devices connected as such via the device model
+(only!) to a domain:
+
+ xl qemu-monitor-command vm1 'info usb'
+  Device 0.2, Port 5, Speed 480 Mb/s, Product Mass Storage
+
+=back
+
 =head1 TMEM
 
 =over 4
diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index e4c25c4..7cfa540 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -275,6 +275,12 @@
 #define LIBXL_HAVE_BUILD_ID 1
 
 /*
+ * LIBXL_HAVE_QEMU_MONITOR_COMMAND indiactes the availability of the
+ * libxl_qemu_monitor_command() function.
+ */
+#define LIBXL_HAVE_QEMU_MONITOR_COMMAND 1
+
+/*
  * libxl ABI compatibility
  *
  * The only guarantee which libxl makes regarding ABI compatibility
@@ -2152,6 +2158,14 @@ void libxl_psr_cat_info_list_free(libxl_psr_cat_info *list, int nr);
 int libxl_fd_set_cloexec(libxl_ctx *ctx, int fd, int cloexec);
 int libxl_fd_set_nonblock(libxl_ctx *ctx, int fd, int nonblock);
 
+/*
+ * Issue a qmp monitor command to the device model of the specified domain.
+ * The function returns the output of the command in a new allocated buffer
+ * via output.
+ */
+int libxl_qemu_monitor_command(libxl_ctx *ctx, uint32_t domid,
+                               const char *command_line, char **output);
+
 #include <libxl_event.h>
 
 #endif /* LIBXL_H */
diff --git a/tools/libxl/libxl_colo_qdisk.c b/tools/libxl/libxl_colo_qdisk.c
index c23b81b..d271d1f 100644
--- a/tools/libxl/libxl_colo_qdisk.c
+++ b/tools/libxl/libxl_colo_qdisk.c
@@ -173,7 +173,7 @@ static void colo_qdisk_save_preresume(libxl__egc *egc,
                     "file.driver=nbd,file.host=%s,file.port=%d,"
                     "file.export=%s,node-name=%s,if=none",
                     host, port, export_name, node);
-    ret = libxl__qmp_hmp(gc, domid, cmd);
+    ret = libxl__qmp_hmp(gc, domid, cmd, NULL);
     if (ret)
         rc = ERROR_FAIL;
 
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index ce8e17a..9f534c4 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1818,7 +1818,8 @@ _hidden int libxl__qmp_x_blockdev_change(libxl__gc *gc, int domid,
                                          const char *parant,
                                          const char *child, const char *node);
 /* run a hmp command in qmp mode */
-_hidden int libxl__qmp_hmp(libxl__gc *gc, int domid, const char *command_line);
+_hidden int libxl__qmp_hmp(libxl__gc *gc, int domid, const char *command_line,
+                           char **out);
 /* close and free the QMP handler */
 _hidden void libxl__qmp_close(libxl__qmp_handler *qmp);
 /* remove the socket file, if the file has already been removed,
diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
index 63c49c5..33883b8 100644
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -1103,14 +1103,48 @@ int libxl__qmp_x_blockdev_change(libxl__gc *gc, int domid, const char *parent,
     return qmp_run_command(gc, domid, "x-blockdev-change", args, NULL, NULL);
 }
 
-int libxl__qmp_hmp(libxl__gc *gc, int domid, const char *command_line)
+static int hmp_callback(libxl__qmp_handler *qmp,
+                        const libxl__json_object *response,
+                        void *opaque)
+{
+    char **output = opaque;
+    GC_INIT(qmp->ctx);
+    int rc = 0;
+
+    if (!output)
+        goto out;
+
+    *output = NULL;
+
+    if (libxl__json_object_is_string(response)) {
+        *output = libxl__strdup(gc, libxl__json_object_get_string(response));
+        goto out;
+    }
+
+    LOG(ERROR, "Response has unexpected format");
+    rc = ERROR_FAIL;
+
+out:
+    return rc;
+}
+
+int libxl__qmp_hmp(libxl__gc *gc, int domid, const char *command_line,
+                   char **output)
 {
     libxl__json_object *args = NULL;
 
     qmp_parameters_add_string(gc, &args, "command-line", command_line);
 
     return qmp_run_command(gc, domid, "human-monitor-command", args,
-                           NULL, NULL);
+                           hmp_callback, output);
+}
+
+int libxl_qemu_monitor_command(libxl_ctx *ctx, uint32_t domid,
+                               const char *command_line, char **output)
+{
+    GC_INIT(ctx);
+
+    return libxl__qmp_hmp(gc, domid, command_line, output);
 }
 
 int libxl__qmp_initializations(libxl__gc *gc, uint32_t domid,
diff --git a/tools/libxl/xl.h b/tools/libxl/xl.h
index e601ca1..0a8c813 100644
--- a/tools/libxl/xl.h
+++ b/tools/libxl/xl.h
@@ -133,6 +133,7 @@ int main_psr_cmt_show(int argc, char **argv);
 int main_psr_cat_cbm_set(int argc, char **argv);
 int main_psr_cat_show(int argc, char **argv);
 #endif
+int main_qemu_monitor_command(int argc, char **argv);
 
 void help(const char *command);
 
diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index 7540fb1..ad2cba5 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -9536,6 +9536,33 @@ int main_psr_hwinfo(int argc, char **argv)
 
 #endif
 
+int main_qemu_monitor_command(int argc, char **argv)
+{
+    int opt;
+    uint32_t domid;
+    char *cmd;
+    char *output;
+    int ret;
+
+    SWITCH_FOREACH_OPT(opt, "", NULL, "qemu-monitor-command", 2) {
+        /* No options */
+    }
+
+    domid = find_domain(argv[optind]);
+    cmd = argv[optind + 1];
+
+    if (argc - optind > 2) {
+        fprintf(stderr, "Invalid arguments.\n");
+        return 1;
+    }
+
+    ret = libxl_qemu_monitor_command(ctx, domid, cmd, &output);
+    if (!ret && output)
+        printf("%s\n", output);
+
+    return ret;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libxl/xl_cmdtable.c b/tools/libxl/xl_cmdtable.c
index 85c1e0f..78786fe 100644
--- a/tools/libxl/xl_cmdtable.c
+++ b/tools/libxl/xl_cmdtable.c
@@ -584,6 +584,11 @@ struct cmd_spec cmd_table[] = {
       "List information about all USB controllers and devices for a domain",
       "<Domain>",
     },
+    { "qemu-monitor-command",
+      &main_qemu_monitor_command, 0, 1,
+      "Issue a qemu monitor command to the device model of a domain",
+      "<Domain> <Command>",
+    },
 };
 
 int cmdtable_len = sizeof(cmd_table)/sizeof(struct cmd_spec);
-- 
2.6.6


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Re: [PATCH v2] libxl: add "xl qemu-monitor-command"

[Dario Faggioli]

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On Mon, 2016-09-05 at 16:11 +0200, Juergen Gross wrote:
> diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
> @@ -1103,14 +1103,48 @@ int libxl__qmp_x_blockdev_change(libxl__gc
> *gc, int domid, const char *parent,
>      return qmp_run_command(gc, domid, "x-blockdev-change", args,
> NULL, NULL);
>  }
>  
> -int libxl__qmp_hmp(libxl__gc *gc, int domid, const char
> *command_line)
> +static int hmp_callback(libxl__qmp_handler *qmp,
> +                        const libxl__json_object *response,
> +                        void *opaque)
> +{
> +    char **output = opaque;
> +    GC_INIT(qmp->ctx);
> +    int rc = 0;
> +
I'm probably being a bit picky, but libxl's CODING_STYLE says rc should
not be initialized.

> +    if (!output)
> +        goto out;
> +
> +    *output = NULL;
> +
> +    if (libxl__json_object_is_string(response)) {
> +        *output = libxl__strdup(gc,
> libxl__json_object_get_string(response));
> +        goto out;
> +    }
> +
> +    LOG(ERROR, "Response has unexpected format");
> +    rc = ERROR_FAIL;
> +
> +out:
> +    return rc;
> +}
> +
Also, aren't we missing calling GC_FREE on the out path?

> +int libxl__qmp_hmp(libxl__gc *gc, int domid, const char
> *command_line,
> +                   char **output)
>  {
>      libxl__json_object *args = NULL;
>  
>      qmp_parameters_add_string(gc, &args, "command-line",
> command_line);
>  
>      return qmp_run_command(gc, domid, "human-monitor-command", args,
> -                           NULL, NULL);
> +                           hmp_callback, output);
> +}
> +
> +int libxl_qemu_monitor_command(libxl_ctx *ctx, uint32_t domid,
> +                               const char *command_line, char
> **output)
> +{
> +    GC_INIT(ctx);
> +
> +    return libxl__qmp_hmp(gc, domid, command_line, output);
>
 GC_FREE; again ?

>  }
> 

> diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
> @@ -9536,6 +9536,33 @@ int main_psr_hwinfo(int argc, char **argv)
>  
>  #endif
>  
> +int main_qemu_monitor_command(int argc, char **argv)
> +{
> +    int opt;
> +    uint32_t domid;
> +    char *cmd;
> +    char *output;
> +    int ret;
> +
> +    SWITCH_FOREACH_OPT(opt, "", NULL, "qemu-monitor-command", 2) {
> +        /* No options */
> +    }
> +
> +    domid = find_domain(argv[optind]);
> +    cmd = argv[optind + 1];
> +
> +    if (argc - optind > 2) {
> +        fprintf(stderr, "Invalid arguments.\n");
> +        return 1;
> +    }
> +
> +    ret = libxl_qemu_monitor_command(ctx, domid, cmd, &output);
> +    if (!ret && output)
> +        printf("%s\n", output);
> +
> +    return ret;
>
Things are not fully consistent yet, but there's an ongoing effort for
having xl terminate with either EXIT_SUCCESS or EXIT_FAILURE. Can you
use them when exit()-ing or, like in this case, returning from a
main_foo() function?

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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Re: [PATCH v2] libxl: add "xl qemu-monitor-command"

[Juergen Gross]

On 06/09/16 10:31, Dario Faggioli wrote:
> On Mon, 2016-09-05 at 16:11 +0200, Juergen Gross wrote:
>> diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
>> @@ -1103,14 +1103,48 @@ int libxl__qmp_x_blockdev_change(libxl__gc
>> *gc, int domid, const char *parent,
>>      return qmp_run_command(gc, domid, "x-blockdev-change", args,
>> NULL, NULL);
>>  }
>>  
>> -int libxl__qmp_hmp(libxl__gc *gc, int domid, const char
>> *command_line)
>> +static int hmp_callback(libxl__qmp_handler *qmp,
>> +                        const libxl__json_object *response,
>> +                        void *opaque)
>> +{
>> +    char **output = opaque;
>> +    GC_INIT(qmp->ctx);
>> +    int rc = 0;
>> +
> I'm probably being a bit picky, but libxl's CODING_STYLE says rc should
> not be initialized.

Okay.

> 
>> +    if (!output)
>> +        goto out;
>> +
>> +    *output = NULL;
>> +
>> +    if (libxl__json_object_is_string(response)) {
>> +        *output = libxl__strdup(gc,
>> libxl__json_object_get_string(response));
>> +        goto out;
>> +    }
>> +
>> +    LOG(ERROR, "Response has unexpected format");
>> +    rc = ERROR_FAIL;
>> +
>> +out:
>> +    return rc;
>> +}
>> +
> Also, aren't we missing calling GC_FREE on the out path?

Yes. And libxl__strdup should use NOGC.

> 
>> +int libxl__qmp_hmp(libxl__gc *gc, int domid, const char
>> *command_line,
>> +                   char **output)
>>  {
>>      libxl__json_object *args = NULL;
>>  
>>      qmp_parameters_add_string(gc, &args, "command-line",
>> command_line);
>>  
>>      return qmp_run_command(gc, domid, "human-monitor-command", args,
>> -                           NULL, NULL);
>> +                           hmp_callback, output);
>> +}
>> +
>> +int libxl_qemu_monitor_command(libxl_ctx *ctx, uint32_t domid,
>> +                               const char *command_line, char
>> **output)
>> +{
>> +    GC_INIT(ctx);
>> +
>> +    return libxl__qmp_hmp(gc, domid, command_line, output);
>>
>  GC_FREE; again ?

Yep.

> 
>>  }
>>
> 
>> diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
>> @@ -9536,6 +9536,33 @@ int main_psr_hwinfo(int argc, char **argv)
>>  
>>  #endif
>>  
>> +int main_qemu_monitor_command(int argc, char **argv)
>> +{
>> +    int opt;
>> +    uint32_t domid;
>> +    char *cmd;
>> +    char *output;
>> +    int ret;
>> +
>> +    SWITCH_FOREACH_OPT(opt, "", NULL, "qemu-monitor-command", 2) {
>> +        /* No options */
>> +    }
>> +
>> +    domid = find_domain(argv[optind]);
>> +    cmd = argv[optind + 1];
>> +
>> +    if (argc - optind > 2) {
>> +        fprintf(stderr, "Invalid arguments.\n");
>> +        return 1;
>> +    }
>> +
>> +    ret = libxl_qemu_monitor_command(ctx, domid, cmd, &output);
>> +    if (!ret && output)
>> +        printf("%s\n", output);
>> +
>> +    return ret;
>>
> Things are not fully consistent yet, but there's an ongoing effort for
> having xl terminate with either EXIT_SUCCESS or EXIT_FAILURE. Can you
> use them when exit()-ing or, like in this case, returning from a
> main_foo() function?

Sure.


Thanks,

Juergen

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