From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:54932) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RlU8V-0001iU-NB for qemu-devel@nongnu.org; Thu, 12 Jan 2012 18:32:49 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RlU8U-0000M1-76 for qemu-devel@nongnu.org; Thu, 12 Jan 2012 18:32:47 -0500 Received: from e3.ny.us.ibm.com ([32.97.182.143]:45536) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RlU8U-0000Lc-3M for qemu-devel@nongnu.org; Thu, 12 Jan 2012 18:32:46 -0500 Received: from /spool/local by e3.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 12 Jan 2012 18:32:44 -0500 Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q0CNWYpG344764 for ; Thu, 12 Jan 2012 18:32:34 -0500 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q0CNWXQm011262 for ; Thu, 12 Jan 2012 16:32:33 -0700 Message-ID: <4F0F6D90.3010908@linux.vnet.ibm.com> Date: Thu, 12 Jan 2012 17:32:32 -0600 From: Michael Roth MIME-Version: 1.0 References: <1326325801-22825-1-git-send-email-mdroth@linux.vnet.ibm.com> <1326326165-23201-1-git-send-email-mdroth@linux.vnet.ibm.com> <20120112165705.3541bcc9@doriath> In-Reply-To: <20120112165705.3541bcc9@doriath> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2] qemu-ga: add guest-set-support-level command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Luiz Capitulino Cc: aliguori@us.ibm.com, qemu-devel@nongnu.org On 01/12/2012 12:57 PM, Luiz Capitulino wrote: > On Wed, 11 Jan 2012 17:56:05 -0600 > Michael Roth wrote: > >> 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. > > The approach looks fine to me. I have a few review comments below. > >> >> Signed-off-by: Michael Roth >> --- >> 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' } } > > This and GuestAgentCommandInfo are missing good documentation. Looks like > we don't document types as we do in qapi-schema.json. I think we should. > Agreed, I'll precede this with a patch to add the documentation for existing types, and update this patch accordingly. >> { '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' } > > For example, something important that's is not totally clear to me just by > reading the command definition is if 'support_level' refers to the support > level that can be changed by a client. > >> >> ## >> +# @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. > > It's also better to note that if @level< 1.0.0 then the support level will > be set to 1.0.0. > I must've looked at this like 5 times and made a mental note to do that, but in the end it escaped me... >> +# >> +# 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 >> + }; > > Can be const. > >> + 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); > > You could avoid that call, default_support_level and all the _DEFAULT > macros by initializing ga_support_level statically (using the _MIN macros). > The _MIN vs. _DEFAULT is there because we may some time in the future decide to bump up the default support level. We'd still allow fallback to _MIN, if needed, but it may begin to impede progress in the future. But yah, technically since *_MIN == *_DEFAULT I could get rid of them till we need them, I just wanted to make it clear in the code from the start. Same with making the call...ga_set_support_level() may at some point take list of capabilities or something...just wanted to make a central point where all the initialization happens. But I don't mind losing it if that's too much ugly-now-but-might-make-sense-later stuff. >> 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); >