[libvirt] [PATCH 2/2] qemu: Validate the domain after marking the current domain as transient

[Peter Krempa]

On Thu, Feb 23, 2017 at 17:22:44 +0100, Marc Hartmayer wrote:
> On Thu, Feb 23, 2017 at 03:33 PM +0100, Michal Privoznik <mprivozn at redhat.com> wrote:
> > On 02/23/2017 10:44 AM, Marc Hartmayer wrote:
> >> Validate the domain that actually will be started. It's semantically
> >> more clear and also it can detect failures that may have happened in
> >> virDomainObjSetDefTransient().
> >>
> >> Signed-off-by: Marc Hartmayer <mhartmay at linux.vnet.ibm.com>
> >> Reviewed-by: Bjoern Walk <bwalk at linux.vnet.ibm.com>
> >> Reviewed-by: Boris Fiuczynski <fiuczy at linux.vnet.ibm.com>
> >> ---
> >>  src/qemu/qemu_process.c | 6 +++---
> >>  1 file changed, 3 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
> >> index a57d136..bd3a8b8 100644
> >> --- a/src/qemu/qemu_process.c
> >> +++ b/src/qemu/qemu_process.c
> >> @@ -4746,9 +4746,6 @@ qemuProcessInit(virQEMUDriverPtr driver,
> >>                                                        vm->def->os.machine)))
> >>          goto cleanup;
> >>
> >> -    if (qemuProcessStartValidate(driver, vm, priv->qemuCaps, caps, flags) < 0)
> >> -        goto cleanup;
> >> -
> >>      /* Do this upfront, so any part of the startup process can add
> >>       * runtime state to vm->def that won't be persisted. This let's us
> >>       * report implicit runtime defaults in the XML, like vnc listen/socket
> >> @@ -4757,6 +4754,9 @@ qemuProcessInit(virQEMUDriverPtr driver,
> >>      if (virDomainObjSetDefTransient(caps, driver->xmlopt, vm) < 0)
> >>          goto cleanup;
> >>
> >> +    if (qemuProcessStartValidate(driver, vm, priv->qemuCaps, caps, flags) < 0)
> >> +        goto cleanup;
> >> +
> >
> > This needs to be goto stop for the reasons described in the previous e-mail.
> >
> >>      if (flags & VIR_QEMU_PROCESS_START_PRETEND) {
> >>          if (qemuDomainSetPrivatePaths(driver, vm) < 0)
> >>              goto cleanup;
> >>
> >
> > Honestly, I like what we have now better. I mean, SetDefTransient() is
> > very unlikely to fail. It's just doing a copy of domain definition (in a
> > very stupid way, but lets save that for a different discussion).
> > Basically, it will fail on OOM only (which you will not get on a Linux
> > system, unless you really try).
> 
> It's semantically more clear (at least for me) and for example it
> enables us to change some parts of the transient domain before
> validation (affect the transient domain only, not the persistent).

That does not make much sense. If you are changing the definition the
code doing so should make sure that it does not create an invalid
configuration rather than depending on the validation code.
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