* Re: [Qemu-devel] [PATCH v1] qemu: command: rework cpu feature argument support [not found] ` <20161115074212.GB4015667@orkuz.home> @ 2016-11-15 13:44 ` Eduardo Habkost 2016-11-16 13:15 ` [Qemu-devel] [libvirt] " Jiri Denemark 2016-11-17 15:04 ` [Qemu-devel] " Markus Armbruster 0 siblings, 2 replies; 6+ messages in thread From: Eduardo Habkost @ 2016-11-15 13:44 UTC (permalink / raw) To: Collin L. Walling, jjherne, borntraeger, libvir-list, Markus Armbruster, qemu-devel CCing qemu-devel. CCing Markus, in case he has any insights about the interface introspection. On Tue, Nov 15, 2016 at 08:42:12AM +0100, Jiri Denemark wrote: > On Mon, Nov 14, 2016 at 18:02:29 -0200, Eduardo Habkost wrote: > > On Mon, Nov 14, 2016 at 02:26:03PM -0500, Collin L. Walling wrote: > > > cpu features are passed to the qemu command with feature=on/off > > > instead of +/-feature. > > > > > > Signed-off-by: Collin L. Walling <walling@linux.vnet.ibm.com> > > > > If I'm not mistaken, the "feature=on|off" syntax was added on > > QEMU 2.0.0. Does current libvirt support older QEMU versions? > > Of course it does. I'd love to switch to feature=on|off, but how can we > check if QEMU supports it? We can't really start using this syntax > without it. Actually, I was wrong, this was added in v2.4.0. "feat=on|off" needs two things to work (in x86): * Translation of all "foo=bar" options to QOM property setting. This was added in v2.0.0-rc0~162^2 * The actual QOM properties for feature names to be present. They were added in v2.4.0-rc0~101^2~1 So you can be sure "feat=on" is supported by checking if the feature flags are present in device-list-properties output for the CPU model. But device-list-properties is also messy[1]. Maybe we can use the availability of query-cpu-model-expansion to check if we can safely use the new "feat=on|off" system? It's easier than taking all the variables above into account. --- [1] * device-list-properties support for x86 CPU QOM classes will be in QEMU 2.8. * device-list-properties on x86 CPU QOM classes returns an error on QEMU 2.5-2.7. * device-list-properties on x86 CPU classes may crash QEMU in QEMU older than 2.5 (see commit 4c315c27). But: * query-cpu-definitions will probably return the CPU QOM typename in QEMU 2.9+ only. -- Eduardo ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [libvirt] [PATCH v1] qemu: command: rework cpu feature argument support 2016-11-15 13:44 ` [Qemu-devel] [PATCH v1] qemu: command: rework cpu feature argument support Eduardo Habkost @ 2016-11-16 13:15 ` Jiri Denemark 2016-11-16 14:05 ` Eduardo Habkost 2016-11-17 15:04 ` [Qemu-devel] " Markus Armbruster 1 sibling, 1 reply; 6+ messages in thread From: Jiri Denemark @ 2016-11-16 13:15 UTC (permalink / raw) To: Eduardo Habkost Cc: Collin L. Walling, jjherne, borntraeger, libvir-list, Markus Armbruster, qemu-devel On Tue, Nov 15, 2016 at 11:44:00 -0200, Eduardo Habkost wrote: > CCing qemu-devel. > > CCing Markus, in case he has any insights about the interface > introspection. > > On Tue, Nov 15, 2016 at 08:42:12AM +0100, Jiri Denemark wrote: > > On Mon, Nov 14, 2016 at 18:02:29 -0200, Eduardo Habkost wrote: > > > On Mon, Nov 14, 2016 at 02:26:03PM -0500, Collin L. Walling wrote: > > > > cpu features are passed to the qemu command with feature=on/off > > > > instead of +/-feature. > > > > > > > > Signed-off-by: Collin L. Walling <walling@linux.vnet.ibm.com> > > > > > > If I'm not mistaken, the "feature=on|off" syntax was added on > > > QEMU 2.0.0. Does current libvirt support older QEMU versions? > > > > Of course it does. I'd love to switch to feature=on|off, but how can we > > check if QEMU supports it? We can't really start using this syntax > > without it. > > Actually, I was wrong, this was added in v2.4.0. "feat=on|off" > needs two things to work (in x86): > > * Translation of all "foo=bar" options to QOM property setting. > This was added in v2.0.0-rc0~162^2 > * The actual QOM properties for feature names to be present. They > were added in v2.4.0-rc0~101^2~1 > > So you can be sure "feat=on" is supported by checking if the > feature flags are present in device-list-properties output for > the CPU model. But device-list-properties is also messy[1]. > > Maybe we can use the availability of query-cpu-model-expansion to > check if we can safely use the new "feat=on|off" system? It's > easier than taking all the variables above into account. Yeah, this could work since s390 already supports query-cpu-model-expansion. It would cause feature=on|off not to be used on x86_64 with QEMU older than 2.9.0, but I guess that's not a big deal, is it? Jirka ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [libvirt] [PATCH v1] qemu: command: rework cpu feature argument support 2016-11-16 13:15 ` [Qemu-devel] [libvirt] " Jiri Denemark @ 2016-11-16 14:05 ` Eduardo Habkost 2016-11-16 15:44 ` Collin L. Walling 0 siblings, 1 reply; 6+ messages in thread From: Eduardo Habkost @ 2016-11-16 14:05 UTC (permalink / raw) To: Collin L. Walling, jjherne, borntraeger, libvir-list, Markus Armbruster, qemu-devel On Wed, Nov 16, 2016 at 02:15:02PM +0100, Jiri Denemark wrote: > On Tue, Nov 15, 2016 at 11:44:00 -0200, Eduardo Habkost wrote: > > CCing qemu-devel. > > > > CCing Markus, in case he has any insights about the interface > > introspection. > > > > On Tue, Nov 15, 2016 at 08:42:12AM +0100, Jiri Denemark wrote: > > > On Mon, Nov 14, 2016 at 18:02:29 -0200, Eduardo Habkost wrote: > > > > On Mon, Nov 14, 2016 at 02:26:03PM -0500, Collin L. Walling wrote: > > > > > cpu features are passed to the qemu command with feature=on/off > > > > > instead of +/-feature. > > > > > > > > > > Signed-off-by: Collin L. Walling <walling@linux.vnet.ibm.com> > > > > > > > > If I'm not mistaken, the "feature=on|off" syntax was added on > > > > QEMU 2.0.0. Does current libvirt support older QEMU versions? > > > > > > Of course it does. I'd love to switch to feature=on|off, but how can we > > > check if QEMU supports it? We can't really start using this syntax > > > without it. > > > > Actually, I was wrong, this was added in v2.4.0. "feat=on|off" > > needs two things to work (in x86): > > > > * Translation of all "foo=bar" options to QOM property setting. > > This was added in v2.0.0-rc0~162^2 > > * The actual QOM properties for feature names to be present. They > > were added in v2.4.0-rc0~101^2~1 > > > > So you can be sure "feat=on" is supported by checking if the > > feature flags are present in device-list-properties output for > > the CPU model. But device-list-properties is also messy[1]. > > > > Maybe we can use the availability of query-cpu-model-expansion to > > check if we can safely use the new "feat=on|off" system? It's > > easier than taking all the variables above into account. > > Yeah, this could work since s390 already supports > query-cpu-model-expansion. It would cause feature=on|off not to be used > on x86_64 with QEMU older than 2.9.0, but I guess that's not a big deal, > is it? Not a problem, as we have no plans to remove +feat/-feat support in x86 anymore. -- Eduardo ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [libvirt] [PATCH v1] qemu: command: rework cpu feature argument support 2016-11-16 14:05 ` Eduardo Habkost @ 2016-11-16 15:44 ` Collin L. Walling 0 siblings, 0 replies; 6+ messages in thread From: Collin L. Walling @ 2016-11-16 15:44 UTC (permalink / raw) To: Eduardo Habkost, jjherne, borntraeger, libvir-list, Markus Armbruster, qemu-devel On 11/16/2016 09:05 AM, Eduardo Habkost wrote: > On Wed, Nov 16, 2016 at 02:15:02PM +0100, Jiri Denemark wrote: >> On Tue, Nov 15, 2016 at 11:44:00 -0200, Eduardo Habkost wrote: >>> CCing qemu-devel. >>> >>> CCing Markus, in case he has any insights about the interface >>> introspection. >>> >>> On Tue, Nov 15, 2016 at 08:42:12AM +0100, Jiri Denemark wrote: >>>> On Mon, Nov 14, 2016 at 18:02:29 -0200, Eduardo Habkost wrote: >>>>> On Mon, Nov 14, 2016 at 02:26:03PM -0500, Collin L. Walling wrote: >>>>>> cpu features are passed to the qemu command with feature=on/off >>>>>> instead of +/-feature. >>>>>> >>>>>> Signed-off-by: Collin L. Walling <walling@linux.vnet.ibm.com> >>>>> If I'm not mistaken, the "feature=on|off" syntax was added on >>>>> QEMU 2.0.0. Does current libvirt support older QEMU versions? >>>> Of course it does. I'd love to switch to feature=on|off, but how can we >>>> check if QEMU supports it? We can't really start using this syntax >>>> without it. >>> Actually, I was wrong, this was added in v2.4.0. "feat=on|off" >>> needs two things to work (in x86): >>> >>> * Translation of all "foo=bar" options to QOM property setting. >>> This was added in v2.0.0-rc0~162^2 >>> * The actual QOM properties for feature names to be present. They >>> were added in v2.4.0-rc0~101^2~1 >>> >>> So you can be sure "feat=on" is supported by checking if the >>> feature flags are present in device-list-properties output for >>> the CPU model. But device-list-properties is also messy[1]. >>> >>> Maybe we can use the availability of query-cpu-model-expansion to >>> check if we can safely use the new "feat=on|off" system? It's >>> easier than taking all the variables above into account. >> Yeah, this could work since s390 already supports >> query-cpu-model-expansion. It would cause feature=on|off not to be used >> on x86_64 with QEMU older than 2.9.0, but I guess that's not a big deal, >> is it? > Not a problem, as we have no plans to remove +feat/-feat support > in x86 anymore. > Beautiful. Thanks for your responses everyone. :) ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH v1] qemu: command: rework cpu feature argument support 2016-11-15 13:44 ` [Qemu-devel] [PATCH v1] qemu: command: rework cpu feature argument support Eduardo Habkost 2016-11-16 13:15 ` [Qemu-devel] [libvirt] " Jiri Denemark @ 2016-11-17 15:04 ` Markus Armbruster 2016-11-17 16:36 ` Eduardo Habkost 1 sibling, 1 reply; 6+ messages in thread From: Markus Armbruster @ 2016-11-17 15:04 UTC (permalink / raw) To: Eduardo Habkost Cc: Collin L. Walling, jjherne, borntraeger, libvir-list, qemu-devel Eduardo Habkost <ehabkost@redhat.com> writes: > CCing qemu-devel. > > CCing Markus, in case he has any insights about the interface > introspection. > > On Tue, Nov 15, 2016 at 08:42:12AM +0100, Jiri Denemark wrote: >> On Mon, Nov 14, 2016 at 18:02:29 -0200, Eduardo Habkost wrote: >> > On Mon, Nov 14, 2016 at 02:26:03PM -0500, Collin L. Walling wrote: >> > > cpu features are passed to the qemu command with feature=on/off >> > > instead of +/-feature. >> > > >> > > Signed-off-by: Collin L. Walling <walling@linux.vnet.ibm.com> >> > >> > If I'm not mistaken, the "feature=on|off" syntax was added on >> > QEMU 2.0.0. Does current libvirt support older QEMU versions? >> >> Of course it does. I'd love to switch to feature=on|off, but how can we >> check if QEMU supports it? We can't really start using this syntax >> without it. > > Actually, I was wrong, this was added in v2.4.0. "feat=on|off" > needs two things to work (in x86): > > * Translation of all "foo=bar" options to QOM property setting. > This was added in v2.0.0-rc0~162^2 > * The actual QOM properties for feature names to be present. They > were added in v2.4.0-rc0~101^2~1 > > So you can be sure "feat=on" is supported by checking if the > feature flags are present in device-list-properties output for > the CPU model. But device-list-properties is also messy[1]. > > Maybe we can use the availability of query-cpu-model-expansion to > check if we can safely use the new "feat=on|off" system? It's > easier than taking all the variables above into account. > > --- > > [1] * device-list-properties support for x86 CPU QOM classes > will be in QEMU 2.8. > * device-list-properties on x86 CPU QOM classes returns > an error on QEMU 2.5-2.7. > * device-list-properties on x86 CPU classes may crash QEMU in > QEMU older than 2.5 (see commit 4c315c27). > But: > * query-cpu-definitions will probably return the CPU QOM > typename in QEMU 2.9+ only. In other words: * feature=on|off works since 2.4, but what's the best way to probe for it? * device-list-properties can act as a witness, but there are two problems: you need to map between CPU model and QOM typename to use it, and it can fail or even crash before 2.8. * 2.9 will take provide the information to map between CPU model and QOM typename. I guess the sane choice is to probe for the CPU model - QOM typename mapping information, and if it's there, assume device-list-properties and feature=on|off work. Eduardo, what do you think? ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH v1] qemu: command: rework cpu feature argument support 2016-11-17 15:04 ` [Qemu-devel] " Markus Armbruster @ 2016-11-17 16:36 ` Eduardo Habkost 0 siblings, 0 replies; 6+ messages in thread From: Eduardo Habkost @ 2016-11-17 16:36 UTC (permalink / raw) To: Markus Armbruster Cc: Collin L. Walling, jjherne, borntraeger, libvir-list, qemu-devel On Thu, Nov 17, 2016 at 04:04:33PM +0100, Markus Armbruster wrote: > Eduardo Habkost <ehabkost@redhat.com> writes: > > > CCing qemu-devel. > > > > CCing Markus, in case he has any insights about the interface > > introspection. > > > > On Tue, Nov 15, 2016 at 08:42:12AM +0100, Jiri Denemark wrote: > >> On Mon, Nov 14, 2016 at 18:02:29 -0200, Eduardo Habkost wrote: > >> > On Mon, Nov 14, 2016 at 02:26:03PM -0500, Collin L. Walling wrote: > >> > > cpu features are passed to the qemu command with feature=on/off > >> > > instead of +/-feature. > >> > > > >> > > Signed-off-by: Collin L. Walling <walling@linux.vnet.ibm.com> > >> > > >> > If I'm not mistaken, the "feature=on|off" syntax was added on > >> > QEMU 2.0.0. Does current libvirt support older QEMU versions? > >> > >> Of course it does. I'd love to switch to feature=on|off, but how can we > >> check if QEMU supports it? We can't really start using this syntax > >> without it. > > > > Actually, I was wrong, this was added in v2.4.0. "feat=on|off" > > needs two things to work (in x86): > > > > * Translation of all "foo=bar" options to QOM property setting. > > This was added in v2.0.0-rc0~162^2 > > * The actual QOM properties for feature names to be present. They > > were added in v2.4.0-rc0~101^2~1 > > > > So you can be sure "feat=on" is supported by checking if the > > feature flags are present in device-list-properties output for > > the CPU model. But device-list-properties is also messy[1]. > > > > Maybe we can use the availability of query-cpu-model-expansion to > > check if we can safely use the new "feat=on|off" system? It's > > easier than taking all the variables above into account. > > > > --- > > > > [1] * device-list-properties support for x86 CPU QOM classes > > will be in QEMU 2.8. > > * device-list-properties on x86 CPU QOM classes returns > > an error on QEMU 2.5-2.7. > > * device-list-properties on x86 CPU classes may crash QEMU in > > QEMU older than 2.5 (see commit 4c315c27). > > But: > > * query-cpu-definitions will probably return the CPU QOM > > typename in QEMU 2.9+ only. > > In other words: > > * feature=on|off works since 2.4, but what's the best way to probe for > it? > > * device-list-properties can act as a witness, but there are two > problems: you need to map between CPU model and QOM typename to use > it, and it can fail or even crash before 2.8. > > * 2.9 will take provide the information to map between CPU model and QOM > typename. > > I guess the sane choice is to probe for the CPU model - QOM typename > mapping information, and if it's there, assume device-list-properties > and feature=on|off work. Eduardo, what do you think? That would work for x86, but not for s390x on QEMU <= 2.8 (where only feat=on|off is supported). Using query-cpu-model-expansion as a witness would work for both s390x and i386, even with QEMU <= 2.8. -- Eduardo ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2016-11-17 16:36 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- [not found] <1479151563-13473-1-git-send-email-walling@linux.vnet.ibm.com> [not found] ` <1479151563-13473-2-git-send-email-walling@linux.vnet.ibm.com> [not found] ` <20161114200229.GG5057@thinpad.lan.raisama.net> [not found] ` <20161115074212.GB4015667@orkuz.home> 2016-11-15 13:44 ` [Qemu-devel] [PATCH v1] qemu: command: rework cpu feature argument support Eduardo Habkost 2016-11-16 13:15 ` [Qemu-devel] [libvirt] " Jiri Denemark 2016-11-16 14:05 ` Eduardo Habkost 2016-11-16 15:44 ` Collin L. Walling 2016-11-17 15:04 ` [Qemu-devel] " Markus Armbruster 2016-11-17 16:36 ` Eduardo Habkost
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