| Message ID | 20190328182810.21497-3-kwolf@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | file-posix: query-qemu-features for auto-read-only | expand |
On 3/28/19 1:28 PM, Kevin Wolf wrote: > auto-read-only=on changed its behaviour in file-posix for the 4.0 > release. This change cannot be detected through the usual mechanisms > like schema introspection. Add a new feature to query-qemu-features to > allow libvirt to detect the presence of the new behaviour. Oddly enough, introspecting the schema is sufficient to learn about this particular feature (that is, until we actually have a runtime feature that requires us to run the command, merely seeing what features the command supports is useful on its own). But that doesn't change the fact that we should keep things as a command. Reviewed-by: Eric Blake <eblake@redhat.com>
Am 28.03.2019 um 19:45 hat Eric Blake geschrieben: > On 3/28/19 1:28 PM, Kevin Wolf wrote: > > auto-read-only=on changed its behaviour in file-posix for the 4.0 > > release. This change cannot be detected through the usual mechanisms > > like schema introspection. Add a new feature to query-qemu-features to > > allow libvirt to detect the presence of the new behaviour. > > Oddly enough, introspecting the schema is sufficient to learn about this > particular feature (that is, until we actually have a runtime feature > that requires us to run the command, merely seeing what features the > command supports is useful on its own). But that doesn't change the fact > that we should keep things as a command. Yes, I thought the same. But without the command, the type would disapear from query-qmp-schema, so it has to be there either way. I think, however, that libvirt should actually run the command, not only test for its presence. Maybe we end up with some case where a new version can't provide the feature unconditionally for some reason, and then we want to be able to turn a static feature into a runtime one. Kevin
On Fri, Mar 29, 2019 at 08:52:13 +0100, Kevin Wolf wrote: > Am 28.03.2019 um 19:45 hat Eric Blake geschrieben: > > On 3/28/19 1:28 PM, Kevin Wolf wrote: > > > auto-read-only=on changed its behaviour in file-posix for the 4.0 > > > release. This change cannot be detected through the usual mechanisms > > > like schema introspection. Add a new feature to query-qemu-features to > > > allow libvirt to detect the presence of the new behaviour. > > > > Oddly enough, introspecting the schema is sufficient to learn about this > > particular feature (that is, until we actually have a runtime feature > > that requires us to run the command, merely seeing what features the > > command supports is useful on its own). But that doesn't change the fact > > that we should keep things as a command. > > Yes, I thought the same. But without the command, the type would > disapear from query-qmp-schema, so it has to be there either way. > > I think, however, that libvirt should actually run the command, not only > test for its presence. Maybe we end up with some case where a new > version can't provide the feature unconditionally for some reason, and > then we want to be able to turn a static feature into a runtime one. I'm definitely going to call the command. Actually I'm working on implementing it right now. One benefit of doing it right away is that we don't have any capability test data for the new version yet, so they will not have to be updated once we'd actually need to call the command.
Kevin Wolf <kwolf@redhat.com> writes: > auto-read-only=on changed its behaviour in file-posix for the 4.0 > release. Commit hash, please. > This change cannot be detected through the usual mechanisms > like schema introspection. Add a new feature to query-qemu-features to > allow libvirt to detect the presence of the new behaviour. > > Signed-off-by: Kevin Wolf <kwolf@redhat.com> > --- > qapi/misc.json | 7 ++++++- > qmp.c | 1 + > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/qapi/misc.json b/qapi/misc.json > index d892f37633..df23c54a65 100644 > --- a/qapi/misc.json > +++ b/qapi/misc.json > @@ -3058,10 +3058,15 @@ > # Information about support for QEMU features that isn't available through > # schema introspection. > # > +# @file-posix-dynamic-auto-read-only: > +# true if auto-read-only=on means that the image file is dynamically reopened > +# read-only or read-write depending on whether any writers are attached to > +# the node. > +# The name @file-posix-dynamic-auto-read-only suggests the semantic change of auto-read-only=on explained in the doc comment applies only to some BlockDrivers (as a non-variant member of BlockdevOptions, auto-read-only applies to all). Which ones exactly? > # Since: 4.0 > ## > { 'struct': 'QemuFeatures', > - 'data': { } } > + 'data': { 'file-posix-dynamic-auto-read-only': 'bool' } } > > ## > # @query-qemu-features: > diff --git a/qmp.c b/qmp.c > index 0aad533eca..2a887c1e7d 100644 > --- a/qmp.c > +++ b/qmp.c > @@ -723,6 +723,7 @@ QemuFeatures *qmp_query_qemu_features(Error **errp) > QemuFeatures *caps = g_new(QemuFeatures, 1); > > *caps = (QemuFeatures) { > + .file_posix_dynamic_auto_read_only = true, > }; > > return caps; Running the command provides no additional information over schema introspection. Kind of contradicts "Information about support for QEMU features that isn't available through schema introspection" :)
On Fri, Mar 29, 2019 at 10:57:55 +0100, Markus Armbruster wrote: > Kevin Wolf <kwolf@redhat.com> writes: > > > auto-read-only=on changed its behaviour in file-posix for the 4.0 > > release. > > Commit hash, please. > > > This change cannot be detected through the usual mechanisms > > like schema introspection. Add a new feature to query-qemu-features to > > allow libvirt to detect the presence of the new behaviour. > > > > Signed-off-by: Kevin Wolf <kwolf@redhat.com> > > --- > > qapi/misc.json | 7 ++++++- > > qmp.c | 1 + > > 2 files changed, 7 insertions(+), 1 deletion(-) [...] > > diff --git a/qmp.c b/qmp.c > > index 0aad533eca..2a887c1e7d 100644 > > --- a/qmp.c > > +++ b/qmp.c > > @@ -723,6 +723,7 @@ QemuFeatures *qmp_query_qemu_features(Error **errp) > > QemuFeatures *caps = g_new(QemuFeatures, 1); > > > > *caps = (QemuFeatures) { > > + .file_posix_dynamic_auto_read_only = true, > > }; > > > > return caps; > > Running the command provides no additional information over schema > introspection. Kind of contradicts "Information about support for QEMU > features that isn't available through schema introspection" :) Honestly I don't care whether it provides information on top of the schema. There is a long term defficiency which does not allow us to detect changes in the code as they are invisible to libvirt's means of capability detection. Then it results in monstrosities like: https://libvirt.org/git/?p=libvirt.git;a=blob;f=src/qemu/qemu_capabilities.c;h=56228e7a36e78ad2ff52a5e83d4af144deea9528;hb=HEAD#l4309 Or you get ad-hoc hacks which add a useless command just to have something exposed in the schema: commit e1ca8f7e1915496148f6e0ce1f7c2309af013312 Author: Gerd Hoffmann <kraxel@redhat.com> Date: Thu Nov 22 08:16:13 2018 +0100 qapi: add query-display-options command Add query-display-options command, which allows querying the qemu display configuration. This isn't particularly useful, except it exposes QAPI type DisplayOptions in query-qmp-schema, so that libvirt can discover recently added -display parameter rendernode (commit d4dc4ab133b). Works around lack of sufficiently powerful command line introspection. Whether there is a static entry in the QMP schema (which feels wrong btw as it does not actually expose something which is regarding the interaction with QMP) or something like this, we need it yesterday. I don't want to add version checks any more.
Peter Krempa <pkrempa@redhat.com> writes: [...] > Whether there is a static entry in the QMP schema (which feels wrong > btw as it does not actually expose something which is regarding the > interaction with QMP) or something like this, we need it yesterday. I > don't want to add version checks any more. I do understand the pressing need for a solution. But beware of "we need to do something, $this is something, therefore we need to do $this".
Markus Armbruster <armbru@redhat.com> writes: > Kevin Wolf <kwolf@redhat.com> writes: > >> auto-read-only=on changed its behaviour in file-posix for the 4.0 >> release. > > Commit hash, please. I guess it's commit 23dece19da4 "file-posix: Make auto-read-only dynamic". >> This change cannot be detected through the usual mechanisms >> like schema introspection. Add a new feature to query-qemu-features to >> allow libvirt to detect the presence of the new behaviour. >> >> Signed-off-by: Kevin Wolf <kwolf@redhat.com> >> --- >> qapi/misc.json | 7 ++++++- >> qmp.c | 1 + >> 2 files changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/qapi/misc.json b/qapi/misc.json >> index d892f37633..df23c54a65 100644 >> --- a/qapi/misc.json >> +++ b/qapi/misc.json >> @@ -3058,10 +3058,15 @@ >> # Information about support for QEMU features that isn't available through >> # schema introspection. >> # >> +# @file-posix-dynamic-auto-read-only: >> +# true if auto-read-only=on means that the image file is dynamically reopened >> +# read-only or read-write depending on whether any writers are attached to >> +# the node. >> +# > > The name @file-posix-dynamic-auto-read-only suggests the semantic change > of auto-read-only=on explained in the doc comment applies only to some > BlockDrivers (as a non-variant member of BlockdevOptions, auto-read-only > applies to all). Which ones exactly? Kevin answered this on IRC. In my words (and possibly with my mistakes): @auto-read-only is advisory, as documented: # @auto-read-only: if true and @read-only is false, QEMU may automatically # decide not to open the image read-write as requested, but # fall back to read-only instead (and switch between the modes # later), e.g. depending on whether the image file is writable # or whether a writing user is attached to the node # (default: false, since 3.1) Note the "QEMU may". The file-posix drivers always honor it. These are "file", "host_device", "host_cdrom" on a POSIX host, but not on a Windows host. No other driver does. The semantic change we're trying to convey is the following. Before commit 23dece19da4, these drivers did not make use of "(and switch between the modes later)". Since then, they do: they switch from read-only to read/write only when the first writer appears, and switch back to read-only when the last writer disappears. The "posix" in @file-posix-dynamic-auto-read-only feels weird. To make sense of it, you need to know on what kind of host QEMU runs. If we ever implement it for Windows hosts, we'd get do add @file-windows-posix-dynamic-auto-read-only. What about instead adding @file-dynamic-auto-read-only with a suitable compile-time conditional? [...]
On Fri, Mar 29, 2019 at 14:05:46 +0100, Markus Armbruster wrote: > Peter Krempa <pkrempa@redhat.com> writes: > > [...] > > Whether there is a static entry in the QMP schema (which feels wrong > > btw as it does not actually expose something which is regarding the > > interaction with QMP) or something like this, we need it yesterday. I > > don't want to add version checks any more. > > I do understand the pressing need for a solution. But beware of "we > need to do something, $this is something, therefore we need to do > $this". Well, then that tends to result in a perpetual search for the optimal solution while libvirt is stuck with adding version checks or false witnesses (checking that something not entirely relevant, which was added at the same time, is present). So, is the issue that fixes to code which are always unconditionally present would show up both in the new command and in the schema? In the case of fixes this will always happen. As I've tried to say in the first reply a solution like this feels much better than trying to stuff it somehow into the QMP schema without an command. If a fix to the code is advertised it does not have much to do with QMP itself, thus adding anything to QMP schema only would feel partially odd.
Peter Krempa <pkrempa@redhat.com> writes: > On Fri, Mar 29, 2019 at 14:05:46 +0100, Markus Armbruster wrote: >> Peter Krempa <pkrempa@redhat.com> writes: >> >> [...] >> > Whether there is a static entry in the QMP schema (which feels wrong >> > btw as it does not actually expose something which is regarding the >> > interaction with QMP) or something like this, we need it yesterday. I >> > don't want to add version checks any more. >> >> I do understand the pressing need for a solution. But beware of "we >> need to do something, $this is something, therefore we need to do >> $this". > > Well, then that tends to result in a perpetual search for the optimal > solution while libvirt is stuck with adding version checks or false > witnesses (checking that something not entirely relevant, which was > added at the same time, is present). "Tends to" yes. "Does" only if we fail to pick a solution. All I wanted to say was "beware of first past the post". I did not mean to say "all that matters is getting to the post prettily, not when". > So, is the issue that fixes to code which are always unconditionally > present would show up both in the new command and in the schema? In the > case of fixes this will always happen. As I've tried to say in the > first reply a solution like this feels much better than trying to stuff > it somehow into the QMP schema without an command. If a fix to the code > is advertised it does not have much to do with QMP itself, thus adding > anything to QMP schema only would feel partially odd. I'm not sure I understand. The proposed solution puts the information in the schema. It also makes it available in the result of the new command. But why bother running the new command when you already run query-qmp-schema?
Markus Armbruster <armbru@redhat.com> writes: > Markus Armbruster <armbru@redhat.com> writes: > >> Kevin Wolf <kwolf@redhat.com> writes: >> >>> auto-read-only=on changed its behaviour in file-posix for the 4.0 >>> release. >> >> Commit hash, please. > > I guess it's commit 23dece19da4 "file-posix: Make auto-read-only > dynamic". > >>> This change cannot be detected through the usual mechanisms >>> like schema introspection. Add a new feature to query-qemu-features to >>> allow libvirt to detect the presence of the new behaviour. >>> >>> Signed-off-by: Kevin Wolf <kwolf@redhat.com> [...] > The "posix" in @file-posix-dynamic-auto-read-only feels weird. To make > sense of it, you need to know on what kind of host QEMU runs. If we > ever implement it for Windows hosts, we'd get do add > @file-windows-posix-dynamic-auto-read-only. > > What about instead adding @file-dynamic-auto-read-only with a suitable > compile-time conditional? > > [...] Incremental patch: diff --git a/qapi/misc.json b/qapi/misc.json index df23c54a65..36b5ceb595 100644 --- a/qapi/misc.json +++ b/qapi/misc.json @@ -3058,7 +3058,7 @@ # Information about support for QEMU features that isn't available through # schema introspection. # -# @file-posix-dynamic-auto-read-only: +# @file-dynamic-auto-read-only: # true if auto-read-only=on means that the image file is dynamically reopened # read-only or read-write depending on whether any writers are attached to # the node. @@ -3066,7 +3066,9 @@ # Since: 4.0 ## { 'struct': 'QemuFeatures', - 'data': { 'file-posix-dynamic-auto-read-only': 'bool' } } + 'data': { + 'file-dynamic-auto-read-only': { 'type': 'bool', + 'if': 'defined(CONFIG_POSIX)' } } } ## # @query-qemu-features: diff --git a/qmp.c b/qmp.c index 2a887c1e7d..7a4e8d5935 100644 --- a/qmp.c +++ b/qmp.c @@ -723,7 +723,7 @@ QemuFeatures *qmp_query_qemu_features(Error **errp) QemuFeatures *caps = g_new(QemuFeatures, 1); *caps = (QemuFeatures) { - .file_posix_dynamic_auto_read_only = true, + .file_dynamic_auto_read_only = true, }; return caps;
Markus Armbruster <armbru@redhat.com> writes: > Markus Armbruster <armbru@redhat.com> writes: > >> Markus Armbruster <armbru@redhat.com> writes: >> >>> Kevin Wolf <kwolf@redhat.com> writes: >>> >>>> auto-read-only=on changed its behaviour in file-posix for the 4.0 >>>> release. >>> >>> Commit hash, please. >> >> I guess it's commit 23dece19da4 "file-posix: Make auto-read-only >> dynamic". >> >>>> This change cannot be detected through the usual mechanisms >>>> like schema introspection. Add a new feature to query-qemu-features to >>>> allow libvirt to detect the presence of the new behaviour. >>>> >>>> Signed-off-by: Kevin Wolf <kwolf@redhat.com> > [...] >> The "posix" in @file-posix-dynamic-auto-read-only feels weird. To make >> sense of it, you need to know on what kind of host QEMU runs. If we >> ever implement it for Windows hosts, we'd get do add >> @file-windows-posix-dynamic-auto-read-only. >> >> What about instead adding @file-dynamic-auto-read-only with a suitable >> compile-time conditional? >> >> [...] > > Incremental patch: Too fast, use this one. diff --git a/qapi/misc.json b/qapi/misc.json index df23c54a65..36b5ceb595 100644 --- a/qapi/misc.json +++ b/qapi/misc.json @@ -3058,7 +3058,7 @@ # Information about support for QEMU features that isn't available through # schema introspection. # -# @file-posix-dynamic-auto-read-only: +# @file-dynamic-auto-read-only: # true if auto-read-only=on means that the image file is dynamically reopened # read-only or read-write depending on whether any writers are attached to # the node. @@ -3066,7 +3066,9 @@ # Since: 4.0 ## { 'struct': 'QemuFeatures', - 'data': { 'file-posix-dynamic-auto-read-only': 'bool' } } + 'data': { + 'file-dynamic-auto-read-only': { 'type': 'bool', + 'if': 'defined(CONFIG_POSIX)' } } } ## # @query-qemu-features: diff --git a/qmp.c b/qmp.c index 2a887c1e7d..2f5a7d7a2e 100644 --- a/qmp.c +++ b/qmp.c @@ -723,7 +723,9 @@ QemuFeatures *qmp_query_qemu_features(Error **errp) QemuFeatures *caps = g_new(QemuFeatures, 1); *caps = (QemuFeatures) { - .file_posix_dynamic_auto_read_only = true, +#ifdef CONFIG_POSIX + .file_dynamic_auto_read_only = true, +#endif }; return caps; diff --git a/scripts/qapi/visit.py b/scripts/qapi/visit.py index 826b8066e1..ad14fadf54 100644 --- a/scripts/qapi/visit.py +++ b/scripts/qapi/visit.py @@ -110,14 +110,9 @@ void visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **errp) } ''') - # 'goto out' produced for base, for each member, and if variants were - # present - if base or members or variants: - ret += mcgen(''' - -out: -''') ret += mcgen(''' + goto out; /* suppress unused label warning */ +out: error_propagate(errp, err); } ''')
Am 29.03.2019 um 17:19 hat Markus Armbruster geschrieben: > Markus Armbruster <armbru@redhat.com> writes: > > > Markus Armbruster <armbru@redhat.com> writes: > > > >> Markus Armbruster <armbru@redhat.com> writes: > >> > >>> Kevin Wolf <kwolf@redhat.com> writes: > >>> > >>>> auto-read-only=on changed its behaviour in file-posix for the 4.0 > >>>> release. > >>> > >>> Commit hash, please. > >> > >> I guess it's commit 23dece19da4 "file-posix: Make auto-read-only > >> dynamic". > >> > >>>> This change cannot be detected through the usual mechanisms > >>>> like schema introspection. Add a new feature to query-qemu-features to > >>>> allow libvirt to detect the presence of the new behaviour. > >>>> > >>>> Signed-off-by: Kevin Wolf <kwolf@redhat.com> > > [...] > >> The "posix" in @file-posix-dynamic-auto-read-only feels weird. To make > >> sense of it, you need to know on what kind of host QEMU runs. If we > >> ever implement it for Windows hosts, we'd get do add > >> @file-windows-posix-dynamic-auto-read-only. > >> > >> What about instead adding @file-dynamic-auto-read-only with a suitable > >> compile-time conditional? > >> > >> [...] > > > > Incremental patch: > > Too fast, use this one. > > diff --git a/qapi/misc.json b/qapi/misc.json > index df23c54a65..36b5ceb595 100644 > --- a/qapi/misc.json > +++ b/qapi/misc.json > @@ -3058,7 +3058,7 @@ > # Information about support for QEMU features that isn't available through > # schema introspection. > # > -# @file-posix-dynamic-auto-read-only: > +# @file-dynamic-auto-read-only: > # true if auto-read-only=on means that the image file is dynamically reopened > # read-only or read-write depending on whether any writers are attached to > # the node. > @@ -3066,7 +3066,9 @@ > # Since: 4.0 > ## > { 'struct': 'QemuFeatures', > - 'data': { 'file-posix-dynamic-auto-read-only': 'bool' } } > + 'data': { > + 'file-dynamic-auto-read-only': { 'type': 'bool', > + 'if': 'defined(CONFIG_POSIX)' } } } I don't think there is a good reason to make the field conditional. What should be conditional is its value: diff --git a/qapi/misc.json b/qapi/misc.json index df23c54a65..a460fd2acc 100644 --- a/qapi/misc.json +++ b/qapi/misc.json @@ -3058,7 +3058,7 @@ # Information about support for QEMU features that isn't available through # schema introspection. # -# @file-posix-dynamic-auto-read-only: +# @file-dynamic-auto-read-only: # true if auto-read-only=on means that the image file is dynamically reopened # read-only or read-write depending on whether any writers are attached to # the node. @@ -3066,7 +3066,7 @@ # Since: 4.0 ## { 'struct': 'QemuFeatures', - 'data': { 'file-posix-dynamic-auto-read-only': 'bool' } } + 'data': { 'file-dynamic-auto-read-only': 'bool' } } ## # @query-qemu-features: diff --git a/qmp.c b/qmp.c index 2a887c1e7d..3d3c300dc6 100644 --- a/qmp.c +++ b/qmp.c @@ -723,7 +723,11 @@ QemuFeatures *qmp_query_qemu_features(Error **errp) QemuFeatures *caps = g_new(QemuFeatures, 1); *caps = (QemuFeatures) { - .file_posix_dynamic_auto_read_only = true, +#ifdef CONFIG_POSIX + .file_dynamic_auto_read_only = true, +#else + .file_dynamic_auto_read_only = false, +#endif }; return caps;
Am 29.03.2019 um 14:14 hat Markus Armbruster geschrieben: > Markus Armbruster <armbru@redhat.com> writes: > > > Kevin Wolf <kwolf@redhat.com> writes: > > > >> auto-read-only=on changed its behaviour in file-posix for the 4.0 > >> release. > > > > Commit hash, please. > > I guess it's commit 23dece19da4 "file-posix: Make auto-read-only > dynamic". Yes. > >> This change cannot be detected through the usual mechanisms > >> like schema introspection. Add a new feature to query-qemu-features to > >> allow libvirt to detect the presence of the new behaviour. > >> > >> Signed-off-by: Kevin Wolf <kwolf@redhat.com> > >> --- > >> qapi/misc.json | 7 ++++++- > >> qmp.c | 1 + > >> 2 files changed, 7 insertions(+), 1 deletion(-) > >> > >> diff --git a/qapi/misc.json b/qapi/misc.json > >> index d892f37633..df23c54a65 100644 > >> --- a/qapi/misc.json > >> +++ b/qapi/misc.json > >> @@ -3058,10 +3058,15 @@ > >> # Information about support for QEMU features that isn't available through > >> # schema introspection. > >> # > >> +# @file-posix-dynamic-auto-read-only: > >> +# true if auto-read-only=on means that the image file is dynamically reopened > >> +# read-only or read-write depending on whether any writers are attached to > >> +# the node. > >> +# > > > > The name @file-posix-dynamic-auto-read-only suggests the semantic change > > of auto-read-only=on explained in the doc comment applies only to some > > BlockDrivers (as a non-variant member of BlockdevOptions, auto-read-only > > applies to all). Which ones exactly? > > Kevin answered this on IRC. In my words (and possibly with my > mistakes): > > @auto-read-only is advisory, as documented: > > # @auto-read-only: if true and @read-only is false, QEMU may automatically > # decide not to open the image read-write as requested, but > # fall back to read-only instead (and switch between the modes > # later), e.g. depending on whether the image file is writable > # or whether a writing user is attached to the node > # (default: false, since 3.1) > > Note the "QEMU may". > > The file-posix drivers always honor it. These are "file", > "host_device", "host_cdrom" on a POSIX host, but not on a Windows host. I actually noticed that host_cdrom doesn't implement the permission system callbacks (they would be the same as for the other two drivers, but they aren't hooked up in host_cdrom). First I though this might mean that I broke host_cdrom, but actually such backends should always be read-only, so it might be okay. Does anyone have a physical CD drive available to test it? > No other driver does. This is actually not true. I already mentioned on IRC that some read-only format drivers support it. Specifically, these are: bochs, cloop, dmg But I also gave you wrong information regarding protocol drivers, sorry about that. I grepped for the wrong thing and missed that there are more protocol drivers that support auto-read-only (with the old semantics, fallback in .bdrv_open): curl, gluster, iscsi, nbd, rbd, vvfat > The semantic change we're trying to convey is the following. Before > commit 23dece19da4, these drivers did not make use of "(and switch > between the modes later)". Since then, they do: they switch from > read-only to read/write only when the first writer appears, and switch > back to read-only when the last writer disappears. > > > The "posix" in @file-posix-dynamic-auto-read-only feels weird. To make > sense of it, you need to know on what kind of host QEMU runs. If we > ever implement it for Windows hosts, we'd get do add > @file-windows-posix-dynamic-auto-read-only. > > What about instead adding @file-dynamic-auto-read-only with a suitable > compile-time conditional? I think a management tool ought to know what kind of host it's running its VM on, but I'm fine with file-dynamic-auto-read-only. Kevin
diff --git a/qapi/misc.json b/qapi/misc.json index d892f37633..df23c54a65 100644 --- a/qapi/misc.json +++ b/qapi/misc.json @@ -3058,10 +3058,15 @@ # Information about support for QEMU features that isn't available through # schema introspection. # +# @file-posix-dynamic-auto-read-only: +# true if auto-read-only=on means that the image file is dynamically reopened +# read-only or read-write depending on whether any writers are attached to +# the node. +# # Since: 4.0 ## { 'struct': 'QemuFeatures', - 'data': { } } + 'data': { 'file-posix-dynamic-auto-read-only': 'bool' } } ## # @query-qemu-features: diff --git a/qmp.c b/qmp.c index 0aad533eca..2a887c1e7d 100644 --- a/qmp.c +++ b/qmp.c @@ -723,6 +723,7 @@ QemuFeatures *qmp_query_qemu_features(Error **errp) QemuFeatures *caps = g_new(QemuFeatures, 1); *caps = (QemuFeatures) { + .file_posix_dynamic_auto_read_only = true, }; return caps;
auto-read-only=on changed its behaviour in file-posix for the 4.0 release. This change cannot be detected through the usual mechanisms like schema introspection. Add a new feature to query-qemu-features to allow libvirt to detect the presence of the new behaviour. Signed-off-by: Kevin Wolf <kwolf@redhat.com> --- qapi/misc.json | 7 ++++++- qmp.c | 1 + 2 files changed, 7 insertions(+), 1 deletion(-)