On Thu, Jul 04, 2019 at 10:12:04AM +0200, Greg Kurz wrote: > On Thu, 4 Jul 2019 10:23:57 +1000 > David Gibson <da...@gibson.dropbear.id.au> wrote: > > > On Wed, Jul 03, 2019 at 07:50:12PM +0200, Greg Kurz wrote: > > > ics_set_kvm_state_one() is called either during reset, in which case > > > both 'saved priority' and 'current priority' are equal to 0xff, or > > > during migration. In the latter case, 'saved priority' may differ > > > from 'current priority' only if the interrupt had been masked with > > > the ibm,int-off RTAS call. Instead of aborting QEMU, print out an > > > error and exit. > > > > What's the rationale for this? Doesn't hitting this indicate an error > > in the qemu code, for which an abort is the usual response? > > > > This error can be hit by the destination during migration if the > incoming stream is corrupted. Aborting in this case would mislead > the user into suspecting a bug in the destination QEMU, which isn't > the case.
Rather than a bug in the source qemu? I guess so.
> Appart from that, when the in-kernel XICS is in use, only two functions
> manipulate the ICS state: ics_set_kvm_state_one() and ics_get_kvm_state().
> The code is trivial enough that I don't see a great value in the assert
> in the first place... BTW, it comes from the commit:
>
> commit 11ad93f68195f68cc94d988f2aa50b4d190ee52a
> Author: David Gibson <da...@gibson.dropbear.id.au>
> Date: Thu Sep 26 16:18:44 2013 +1000
>
> xics-kvm: Support for in-kernel XICS interrupt controller
>
> Maybe you remember some context that justified the assert at the
> time ?
It was probably mostly about documenting the invariants that are
supposed to apply here.
>
> > >
> > > Based-on: <156217454083.559957.7359208229523652842.st...@bahia.lan>
> > > Signed-off-by: Greg Kurz <gr...@kaod.org>
> > > ---
> > >
> > > This isn't a bugfix, hence targetting 4.2, but it depends on an actual
> > > fix for 4.1, as mentionned in the Based-on tag.
> > > ---
> > > hw/intc/xics_kvm.c | 17 +++++++++++++++--
> > > 1 file changed, 15 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/hw/intc/xics_kvm.c b/hw/intc/xics_kvm.c
> > > index 2df1f3e92c7e..f8758b928250 100644
> > > --- a/hw/intc/xics_kvm.c
> > > +++ b/hw/intc/xics_kvm.c
> > > @@ -255,8 +255,21 @@ int ics_set_kvm_state_one(ICSState *ics, int srcno,
> > > Error **errp)
> > > state = irq->server;
> > > state |= (uint64_t)(irq->saved_priority & KVM_XICS_PRIORITY_MASK)
> > > << KVM_XICS_PRIORITY_SHIFT;
> > > - if (irq->priority != irq->saved_priority) {
> > > - assert(irq->priority == 0xff);
> > > +
> > > + /*
> > > + * An interrupt can be masked either because the ICS is resetting, in
> > > + * which case we expect 'current priority' and 'saved priority' to be
> > > + * equal to 0xff, or because the guest has called the ibm,int-off
> > > RTAS
> > > + * call, in which case we we have recorded the priority the interrupt
> > > + * had before it was masked in 'saved priority'. If the interrupt
> > > isn't
> > > + * masked, 'saved priority' and 'current priority' are equal (see
> > > + * ics_get_kvm_state()). Make sure we restore a sane state, otherwise
> > > + * fail migration.
> > > + */
> > > + if (irq->priority != irq->saved_priority && irq->priority != 0xff) {
> > > + error_setg(errp, "Corrupted state detected for interrupt source
> > > %d",
> > > + srcno);
> > > + return -EINVAL;
> > > }
> > >
> > > if (irq->priority == 0xff) {
> > >
> >
>
--
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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