Re: [PATCH v2 ppc-for-5.0 2/2] ppc/spapr: Support reboot of secure pseries guest

[David Gibson <david@gibson.dropbear.id.au>]

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65;5803;1cOn Fri, Dec 13, 2019 at 09:34:38AM +0530, Bharata B Rao wrote:
> On Thu, Dec 12, 2019 at 01:27:23PM +0100, Greg Kurz wrote:
> > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > index f11422fc41..25e1a3446e 100644
> > > --- a/hw/ppc/spapr.c
> > > +++ b/hw/ppc/spapr.c
> > > @@ -1597,6 +1597,21 @@ static void spapr_machine_reset(MachineState *machine)
> > >      void *fdt;
> > >      int rc;
> > >  
> > > +    /*
> > > +     * KVM_PPC_SVM_OFF ioctl can fail for secure guests, check and
> > > +     * exit in that case. However check for -ENOTTY explicitly
> > > +     * to ensure that we don't terminate normal guests that are
> > > +     * running on kernels which don't support this ioctl.
> > > +     *
> > > +     * Also, this ioctl returns 0 for normal guests on kernels where
> > > +     * this ioctl is supported.
> > > +     */
> > > +    rc = kvmppc_svm_off();
> > > +    if (rc && rc != -ENOTTY) {
> > 
> > This ioctl can also return -EINVAL if the ultravisor actually failed to move
> > the guest back to non-secure mode or -EBUSY if a vCPU is still running. I
> > agree that the former deserve the VM to be terminated. What about the latter ?
> > Can this happen and if yes, why ? Should we try again as suggested by Alexey ?
> > Could this reveal a bug in QEMU, in which case we should maybe abort ?
> 
> We are in machine reset path, so all vcpus are already paused. So we don't
> expect any vcpus to be running to handle -EBUSY here. Neither do I see any
> sane recovery path from here.

Right.  Because this path should only happen in the case of qemu (or
kernel) error, abort() would also be appropriate.  However, it's not
worth making that a separate case from the other fatal errors.

> 
> As Alexey mentioned earlier, may be we can just stop the VM?
> Do vm_stop() with RUN_STATE_PAUSED or some such reason?
> 
> Regards,
> Bharata.
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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