4:40 a.m.
Get default emulator based on guest's arch, and replace it in domain's
definition after domainPostParseDataAlloc's failure, then alloc again.
This will solve the migration problem because of qemu emulator location error,
especially, from host with to host without qemu-kvm.
This commit will also allow user to create a domain with wrong emulator
location, and correct it to the default one.
zhangjl02 (3):
qemu_domain: introduce qemuDomainPostParseDataDefEmulator
domain_conf: introduce virDomainPostParseDataDefEmulator type
domain_conf: set default emulator into def if it fails to alloc
src/conf/domain_conf.c | 10 +++++++++-
src/conf/domain_conf.h | 2 ++
src/qemu/qemu_domain.c | 18 ++++++++++++++++++
3 files changed, 29 insertions(+), 1 deletion(-)
--
2.35.1.windows.2
4:40 a.m.
New subject: [PATCH 1/3] qemu_domain: introduce qemuDomainPostParseDataDefEmulator
From: zhangjl02 <zhangjl02(a)inspur.com>
qemuDomainPostParseDataDefEmulator will try to get default emulator based on
guest's arch from capabilities, and replace the emulator in definition.
Signed-off-by: zhangjl02 <zhangjl02(a)inspur.com>
---
src/qemu/qemu_domain.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 7974cdb00b..98a4070226 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -5972,6 +5972,23 @@ qemuDomainPostParseDataAlloc(const virDomainDef *def,
}
+static int
+qemuDomainPostParseDataDefEmulator(virDomainDef *def)
+{
+ char *emulator = NULL;
+ struct stat sb;
+ virArch hostArch = virArchFromHost();
+ emulator = virQEMUCapsGetDefaultEmulator(hostArch, def->os.arch);
+ if (stat(emulator, &sb) < 0) {
+ virReportSystemError(errno, _("Cannot check QEMU binary %s"),
+ emulator);
+ return 0;
+ }
+ def->emulator = emulator;
+ return 1;
+}
+
+
static void
qemuDomainPostParseDataFree(void *parseOpaque)
{
@@ -5984,6 +6001,7 @@ qemuDomainPostParseDataFree(void *parseOpaque)
virDomainDefParserConfig virQEMUDriverDomainDefParserConfig = {
.domainPostParseBasicCallback = qemuDomainDefPostParseBasic,
.domainPostParseDataAlloc = qemuDomainPostParseDataAlloc,
+ .domainPostParseDataDefEmulator = qemuDomainPostParseDataDefEmulator,
.domainPostParseDataFree = qemuDomainPostParseDataFree,
.devicesPostParseCallback = qemuDomainDeviceDefPostParse,
.domainPostParseCallback = qemuDomainDefPostParse,
--
2.35.1.windows.2
4:40 a.m.
New subject: [PATCH 2/3] domain_conf: introduce virDomainPostParseDataDefEmulator type
From: zhangjl02 <zhangjl02(a)inspur.com>
Add virDomainPostParseDataDefEmulator typedef. Add a definition callback into
_virDomainDefParserConfig.
Signed-off-by: zhangjl02 <zhangjl02(a)inspur.com>
---
src/conf/domain_conf.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 88a411d00c..86d627136a 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -3130,6 +3130,7 @@ typedef int (*virDomainDefPostParseDataAlloc)(const virDomainDef
*def,
unsigned int parseFlags,
void *opaque,
void **parseOpaque);
+typedef int (*virDomainPostParseDataDefEmulator)(virDomainDef *def);
typedef void (*virDomainDefPostParseDataFree)(void *parseOpaque);
/* Called in appropriate places where the domain conf parser can return failure
@@ -3150,6 +3151,7 @@ struct _virDomainDefParserConfig {
/* driver domain definition callbacks */
virDomainDefPostParseBasicCallback domainPostParseBasicCallback;
virDomainDefPostParseDataAlloc domainPostParseDataAlloc;
+ virDomainPostParseDataDefEmulator domainPostParseDataDefEmulator;
virDomainDefPostParseCallback domainPostParseCallback;
virDomainDeviceDefPostParseCallback devicesPostParseCallback;
virDomainDefAssignAddressesCallback assignAddressesCallback;
--
2.35.1.windows.2
4:40 a.m.
New subject: [PATCH 3/3] domain_conf: set default emulator into def if it fails to alloc
From: zhangjl02 <zhangjl02(a)inspur.com>
When emulator is not found on host, domainPostParseDataAlloc will return 1,
and the domain will fail to start. Call domainPostParseDataDefEmulator to
replace emulator with the default one of guest's arch, and try to alloc again
after domainPostParseDataAlloc's failure. This will increase error tolerance,
if emulator defined in xml is not found on host.
Signed-off-by: zhangjl02 <zhangjl02(a)inspur.com>
---
src/conf/domain_conf.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index bd2884088c..485f66357c 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -6266,7 +6266,15 @@ virDomainDefPostParse(virDomainDef *def,
ret = xmlopt->config.domainPostParseDataAlloc(def, parseFlags,
xmlopt->config.priv,
&data.parseOpaque);
-
+ if (ret == 1){
+ int to_default = 0;
+ to_default = xmlopt->config.domainPostParseDataDefEmulator(def);
+ if (to_default) {
+ ret = xmlopt->config.domainPostParseDataAlloc(def, parseFlags,
+ xmlopt->config.priv,
+ &data.parseOpaque);
+ }
+ }
if (virDomainDefPostParseCheckFailure(def, parseFlags, ret) < 0)
goto cleanup;
localParseOpaque = true;
--
2.35.1.windows.2
2:43 a.m.
New subject: [PATCH 3/3] domain_conf: set default emulator into def if it fails to alloc
On Sat, May 07, 2022 at 17:40:16 +0800, zhangjl02 wrote:
From: zhangjl02 <zhangjl02(a)inspur.com>
When emulator is not found on host, domainPostParseDataAlloc will return 1,
and the domain will fail to start. Call domainPostParseDataDefEmulator to
replace emulator with the default one of guest's arch, and try to alloc again
after domainPostParseDataAlloc's failure. This will increase error tolerance,
if emulator defined in xml is not found on host.
What you describe here is definitely not desired. When the user
specifies an emulator path in the XML we must not change it even if the
emulator is not present and we could theoretically use a different one.
This could mask problems and make users use a different binary without
even knowing about it.
If the user wishes to use the default they can certainly omit the
emulator.
3:12 a.m.
On Sat, May 07, 2022 at 05:40:13PM +0800, zhangjl02 wrote:
Get default emulator based on guest's arch, and replace it in
domain's
definition after domainPostParseDataAlloc's failure, then alloc again.
This will solve the migration problem because of qemu emulator location error,
especially, from host with to host without qemu-kvm.
When you're migrating between hosts it is possible to provide libvirt an
updated XML doc at the time you initiate the migration. This allows you
to change any aspect that doesn't impact guest ABI, so you can provide
an updated emulator binary path at time of migration.
With regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
3:22 a.m.
On Mon, May 09, 2022 at 09:12:51 +0100, Daniel P. Berrangé wrote:
On Sat, May 07, 2022 at 05:40:13PM +0800, zhangjl02 wrote:
> Get default emulator based on guest's arch, and replace it in domain's
> definition after domainPostParseDataAlloc's failure, then alloc again.
> This will solve the migration problem because of qemu emulator location error,
> especially, from host with to host without qemu-kvm.
[please primarily put justification of why you are doing something into
the patches themselves. Apart from making it more obvious to reviewers
it also records the justification in git once patches are commited]
When you're migrating between hosts it is possible to provide
libvirt an
updated XML doc at the time you initiate the migration. This allows you
to change any aspect that doesn't impact guest ABI, so you can provide
an updated emulator binary path at time of migration.
Actually there might be a problem with this. I've discussed this
recently with Jirka.
Specifically the ABI stability check is done on the source of the
migration. This means that the source has to actually parse and
interpret the destination XML too if it's provided by the user.
Now if your source host doesn't have the qemu binary or doesn't have it
in the path you have it on the destination this will fail.
I mentioned to Jirka that I think this is sub-optimal:
1) see problem above
2) the post-parse callbacks might fill in different defaults e.g. if the
destination qemu has different capabilities
3) if it were done on destination, the source portion of the XML can be
parsed without post-parse callbacks as it comes actually from a live
libvirt instance
So with the above if they have problem of qemu not being where they
expect, using of the destination XML will not help.
They might be able to use the hook script to filter it on the
destination though:
https://www.libvirt.org/hooks.html#qemu-guest-migration
3:41 a.m.
On Mon, May 09, 2022 at 10:22:56AM +0200, Peter Krempa wrote:
On Mon, May 09, 2022 at 09:12:51 +0100, Daniel P. Berrangé wrote:
> On Sat, May 07, 2022 at 05:40:13PM +0800, zhangjl02 wrote:
> > Get default emulator based on guest's arch, and replace it in domain's
> > definition after domainPostParseDataAlloc's failure, then alloc again.
> > This will solve the migration problem because of qemu emulator location error,
> > especially, from host with to host without qemu-kvm.
[please primarily put justification of why you are doing something into
the patches themselves. Apart from making it more obvious to reviewers
it also records the justification in git once patches are commited]
> When you're migrating between hosts it is possible to provide libvirt an
> updated XML doc at the time you initiate the migration. This allows you
> to change any aspect that doesn't impact guest ABI, so you can provide
> an updated emulator binary path at time of migration.
Actually there might be a problem with this. I've discussed this
recently with Jirka.
Specifically the ABI stability check is done on the source of the
migration. This means that the source has to actually parse and
interpret the destination XML too if it's provided by the user.
Now if your source host doesn't have the qemu binary or doesn't have it
in the path you have it on the destination this will fail.
I mentioned to Jirka that I think this is sub-optimal:
1) see problem above
2) the post-parse callbacks might fill in different defaults e.g. if the
destination qemu has different capabilities
3) if it were done on destination, the source portion of the XML can be
parsed without post-parse callbacks as it comes actually from a live
libvirt instance
Right so we need to pass the XML to the dest, have its details
expanded, then sent back to the src for ABI checking. Or alternatively
just send the current live XML from src to dest, and let the dest do
the ABI checking in the Prepare step.
So with the above if they have problem of qemu not being where they
expect, using of the destination XML will not help.
Hmm, yes, annoying.
They might be able to use the hook script to filter it on the
destination though:
https://www.libvirt.org/hooks.html#qemu-guest-migration
With regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
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7 comments
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zhangjl02