Recently commands where introduced on the mailing that involved adding
commands to the guest agent that could potentially break older versions
of QEMU. While it's okay to expect that qemu-ga can be updated to support
newer host features, it's unrealistic to require a host to be updated to
support qemu-ga features, or to expect that qemu-ga should be downgraded
in these circumstances, especially considering that a large mix of
guests/agents may be running on a particular host.
To address this, we introduce here a mechanism to set qemu-ga's
feature-set to one that is known to be compatible with
the host/QEMU running the guest. As new commands/options are added, we
can maintain backward-compatibility by adding conditional checks to filter
out host-incompatible functionality based on the host-specified support
level (generally analogous to the host QEMU version) set by the
client.
The current default/minimum support level supports all versions of QEMU
that have had qemu-ga in-tree (0.15.0, 1.0.0) and so should be
backward-compatible with existing hosts/clients.
Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com>
---
qapi-schema-guest.json | 31 ++++++++++++++++++++++++++++-
qemu-ga.c | 46 ++++++++++++++++++++++++++++++++++++++++++++
qga/guest-agent-commands.c | 13 ++++++++++++
qga/guest-agent-core.h | 11 ++++++++++
4 files changed, 100 insertions(+), 1 deletions(-)
diff --git a/qapi-schema-guest.json b/qapi-schema-guest.json
index 5f8a18d..32bc041 100644
--- a/qapi-schema-guest.json
+++ b/qapi-schema-guest.json
@@ -43,15 +43,44 @@
#
# Since: 0.15.0
##
+{ 'type': 'GuestAgentSupportLevel',
+ 'data': { 'major': 'int', 'minor': 'int', 'micro': 'int' } }
{ 'type': 'GuestAgentCommandInfo',
'data': { 'name': 'str', 'enabled': 'bool' } }
{ 'type': 'GuestAgentInfo',
'data': { 'version': 'str',
- 'supported_commands': ['GuestAgentCommandInfo'] } }
+ 'supported_commands': ['GuestAgentCommandInfo']
+ 'support_level': 'GuestAgentSupportLevel' } }
{ 'command': 'guest-info',
'returns': 'GuestAgentInfo' }
##
+# @guest-set-support-level:
+#
+# Set guest agent feature-set to one that is compatible with/supported by
+# the host.
+#
+# Certain commands/options may have dependencies on host
+# version/support-level, such as specific QEMU features (such
+# dependencies will be noted in this schema). By default we assume 1.0.0,
+# which is backward-compatible with QEMU 0.15.0/1.0, and should be compatible
+# with later versions of QEMU as well. To enable newer guest agent features,
+# this command must be issued to raise the support-level to one corresponding
+# to supported host QEMU/KVM/etc capabilities.
+#
+# The currently set support level is obtainable via the guest-info command.
+#
+# @level: Desired host support-level, generally <= host QEMU version
+# level. Note that undefined behavior may occur if a support-level is
+# provided that exceeds the capabilities of the version of QEMU currently
+# running the guest.
+#
+# Returns: Nothing on success
+#
+{ 'command': 'guest-set-support-level',
+ 'data': { 'major': 'int', 'minor': 'int', '*micro': 'int' } }
+
+##
# @guest-shutdown:
#
# Initiate guest-activated shutdown. Note: this is an asynchronous
diff --git a/qemu-ga.c b/qemu-ga.c
index 200bb15..6840233 100644
--- a/qemu-ga.c
+++ b/qemu-ga.c
@@ -28,6 +28,7 @@
#include "qerror.h"
#include "error_int.h"
#include "qapi/qmp-core.h"
+#include "qga-qapi-types.h"
#define QGA_VIRTIO_PATH_DEFAULT "/dev/virtio-ports/org.qemu.guest_agent.0"
#define QGA_PIDFILE_DEFAULT "/var/run/qemu-ga.pid"
@@ -102,6 +103,45 @@ static void usage(const char *cmd)
static void conn_channel_close(GAState *s);
+static GuestAgentSupportLevel ga_support_level;
+
+static int ga_cmp_support_levels(GuestAgentSupportLevel a,
+ GuestAgentSupportLevel b)
+{
+ if (a.major == b.major) {
+ if (a.minor == b.minor) {
+ return a.micro - b.micro;
+ }
+ return a.minor - b.minor;
+ }
+ return a.major - b.major;
+}
+
+bool ga_has_support_level(int major, int minor, int micro)
+{
+ GuestAgentSupportLevel level = { major, minor, micro };
+ return ga_cmp_support_levels(level, ga_support_level) >= 0;
+}
+
+void ga_set_support_level(GuestAgentSupportLevel level)
+{
+ GuestAgentSupportLevel min_support_level = {
+ QGA_SUPPORT_LEVEL_MAJOR_MIN,
+ QGA_SUPPORT_LEVEL_MINOR_MIN,
+ QGA_SUPPORT_LEVEL_MICRO_MIN
+ };
+ if (ga_cmp_support_levels(level, min_support_level) <= 0) {
+ ga_support_level = min_support_level;
+ } else {
+ ga_support_level = level;
+ }
+}
+
+GuestAgentSupportLevel ga_get_support_level(void)
+{
+ return ga_support_level;
+}
+
static const char *ga_log_level_str(GLogLevelFlags level)
{
switch (level & G_LOG_LEVEL_MASK) {
@@ -569,6 +609,11 @@ int main(int argc, char **argv)
GLogLevelFlags log_level = G_LOG_LEVEL_ERROR | G_LOG_LEVEL_CRITICAL;
FILE *log_file = stderr;
GAState *s;
+ GuestAgentSupportLevel default_support_level = {
+ QGA_SUPPORT_LEVEL_MAJOR_DEFAULT,
+ QGA_SUPPORT_LEVEL_MINOR_DEFAULT,
+ QGA_SUPPORT_LEVEL_MICRO_DEFAULT
+ };
module_call_init(MODULE_INIT_QAPI);
@@ -642,6 +687,7 @@ int main(int argc, char **argv)
become_daemon(pidfile);
}
+ ga_set_support_level(default_support_level);
s = g_malloc0(sizeof(GAState));
s->conn_channel = NULL;
s->path = path;
diff --git a/qga/guest-agent-commands.c b/qga/guest-agent-commands.c
index a09c8ca..656dde8 100644
--- a/qga/guest-agent-commands.c
+++ b/qga/guest-agent-commands.c
@@ -62,6 +62,8 @@ struct GuestAgentInfo *qmp_guest_info(Error **err)
char **cmd_list_head, **cmd_list;
info->version = g_strdup(QGA_VERSION);
+ info->support_level = g_malloc0(sizeof(GuestAgentSupportLevel));
+ *info->support_level = ga_get_support_level();
cmd_list_head = cmd_list = qmp_get_command_list();
if (*cmd_list_head == NULL) {
@@ -87,6 +89,17 @@ out:
return info;
}
+void qmp_guest_set_support_level(int64_t major, int64_t minor, bool has_micro,
+ int64_t micro, Error **errp)
+{
+ GuestAgentSupportLevel level = {
+ major,
+ minor,
+ has_micro ? micro : 0
+ };
+ ga_set_support_level(level);
+}
+
void qmp_guest_shutdown(bool has_mode, const char *mode, Error **err)
{
int ret;
diff --git a/qga/guest-agent-core.h b/qga/guest-agent-core.h
index e42b91d..7327e73 100644
--- a/qga/guest-agent-core.h
+++ b/qga/guest-agent-core.h
@@ -12,8 +12,16 @@
*/
#include "qapi/qmp-core.h"
#include "qemu-common.h"
+#include "qga-qapi-types.h"
#define QGA_VERSION "1.0"
+#define QGA_SUPPORT_LEVEL_MAJOR_DEFAULT 1
+#define QGA_SUPPORT_LEVEL_MINOR_DEFAULT 0
+#define QGA_SUPPORT_LEVEL_MICRO_DEFAULT 0
+/* lowest possible support level */
+#define QGA_SUPPORT_LEVEL_MAJOR_MIN 1
+#define QGA_SUPPORT_LEVEL_MINOR_MIN 0
+#define QGA_SUPPORT_LEVEL_MICRO_MIN 0
#define QGA_READ_COUNT_DEFAULT 4 << 10
typedef struct GAState GAState;
@@ -29,3 +37,6 @@ GACommandState *ga_command_state_new(void);
bool ga_logging_enabled(GAState *s);
void ga_disable_logging(GAState *s);
void ga_enable_logging(GAState *s);
+bool ga_has_support_level(int major, int minor, int micro);
+void ga_set_support_level(GuestAgentSupportLevel level);
+GuestAgentSupportLevel ga_get_support_level(void);
--
1.7.4.1
