[PATCH v3 4/6] qemu: tpm: Pass --migration option to swtpm if supported and needed

[Michal Prívozník]

On 10/21/22 13:36, Stefan Berger wrote:
> 
> 
> On 10/21/22 06:55, Michal Prívozník wrote:
>> On 10/18/22 19:04, Stefan Berger wrote:
>>> Pass the --migration option to swtpm if swptm supports it (starting
>>> with v0.8) and if the TPM's state is written on shared storage. If this
>>> is the case apply the 'release-lock-outgoing' parameter with this
>>> option and apply the 'incoming' parameter for incoming migration so that
>>> swtpm releases the file lock on the source side when the state is
>>> migrated
>>> and locks the file on the destination side when the state is received.
>>>
>>> If a started swtpm instance is running with the necessary options of
>>> migrating with share storage then remember this with a flag in the
>>> virDomainTPMPrivateDef.
>>>
>>> Report an error if swtpm does not support the --migration option and an
>>> incoming migration across shared storage is requested.
>>>
>>> Signed-off-by: Stefan Berger <stefanb at linux.ibm.com>
>>> ---
>>>   src/qemu/qemu_migration.c |  8 +++++
>>>   src/qemu/qemu_tpm.c       | 66 ++++++++++++++++++++++++++++++++++++++-
>>>   src/qemu/qemu_tpm.h       |  6 ++++
>>>   3 files changed, 79 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
>>> index 33105cf07b..5b4f4615ee 100644
>>> --- a/src/qemu/qemu_migration.c
>>> +++ b/src/qemu/qemu_migration.c
>>> @@ -38,6 +38,7 @@
>>>   #include "qemu_security.h"
>>>   #include "qemu_slirp.h"
>>>   #include "qemu_block.h"
>>> +#include "qemu_tpm.h"
>>>     #include "domain_audit.h"
>>>   #include "virlog.h"
>>> @@ -2789,6 +2790,13 @@ qemuMigrationSrcBegin(virConnectPtr conn,
>>>           goto cleanup;
>>>       }
>>>   +    if (qemuTPMHasSharedStorage(vm->def) &&
>>> +        !qemuTPMCanMigrateSharedStorage(vm->def)) {
>>
>> This works, but only because qemuValidateDomainDefTPMs() denies two
>> emulated TPMs. I think we can call just qemuTPMCanMigrateSharedStorage()
>> since it already iterates over all TPMs and checks each one individually.
> 
> I am only starting swtpm with the necessary command line options for
> shared storage migration if a) shared storage is detected at the time of
> the start of the VM and b) if swtpm supports shared storage migration at
> all. If it doesn't support it I let you start the VM but won't let you
> migrate.
> 
> 
> qemuTPMCanMigrateSharedStorage() checks whether the running swtpm
> instance can do b). It doesn't check the swtpm executable that you may
> have upgraded or downgraded in the meantime. That's why I need the
> private data.
> 
> So the check above tests whether there is shared storage detected for
> the TPM_EMULATOR (swtpm; only one allowed) and if so whether the
> *running swtpm instance* supports shared storage migration. I think it
> is correct this way.

Ah, good point. So let me fix the other small nits I've raised and merge
these.

Michal