Re: [PATCH v1 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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On Tue, Dec 10, 2019 at 03:03:01PM +1100, Alexey Kardashevskiy wrote:
> 
> 
> On 10/12/2019 14:50, Bharata B Rao wrote:
> > On Tue, Dec 10, 2019 at 02:28:51PM +1100, David Gibson wrote:
> >> On Mon, Dec 09, 2019 at 12:30:12PM +0530, Bharata B Rao wrote:
> >>> A pseries guest can be run as a secure guest on Ultravisor-enabled
> >>> POWER platforms. When such a secure guest is reset, we need to
> >>> release/reset a few resources both on ultravisor and hypervisor side.
> >>> This is achieved by invoking this new ioctl KVM_PPC_SVM_OFF from the
> >>> machine reset path.
> >>>
> >>> As part of this ioctl, the secure guest is essentially transitioned
> >>> back to normal mode so that it can reboot like a regular guest and
> >>> become secure again.
> >>>
> >>> This ioctl has no effect when invoked for a normal guest.
> >>>
> >>> Signed-off-by: Bharata B Rao <bharata@linux.ibm.com>
> >>> ---
> >>>  hw/ppc/spapr.c       | 1 +
> >>>  target/ppc/kvm.c     | 7 +++++++
> >>>  target/ppc/kvm_ppc.h | 6 ++++++
> >>>  3 files changed, 14 insertions(+)
> >>>
> >>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> >>> index f11422fc41..4c7ad3400d 100644
> >>> --- a/hw/ppc/spapr.c
> >>> +++ b/hw/ppc/spapr.c
> >>> @@ -1597,6 +1597,7 @@ static void spapr_machine_reset(MachineState *machine)
> >>>      void *fdt;
> >>>      int rc;
> >>>  
> >>> +    kvmppc_svm_off();
> >>
> >> If you're going to have this return an error value, you should really
> >> check it here.
> > 
> > I could, by spapr_machine_reset() and the callers don't propagate the
> > errors up. So may be I could print a warning instead when ioctl fails?
> 
> An error here means you cannot restart the machine and should probably
> suspend, or try until it is not EBUSY (==all threads have stopped?).

Right, if this fails, something has gone badly wrong.  You should
absolutely print a message, and in fact it might be appropriate to
quit outright.  IIUC the way PEF resets work, a failure here means you
won't be able to boot after the reset, since the guest memory will
still be inaccessible to the host.

-- 
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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