Re: [Qemu-devel] [Qemu-ppc] [PULL 41/44] spapr: change default interrupt mode to 'dual'

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

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On Wed, Jul 10, 2019 at 06:26:09PM +0200, Laurent Vivier wrote:
> On 29/05/2019 08:50, David Gibson wrote:
> > From: Cédric Le Goater <clg@kaod.org>
> > 
> > Now that XIVE support is complete (QEMU emulated and KVM devices),
> > change the pseries machine to advertise both interrupt modes: XICS
> > (P7/P8) and XIVE (P9).
> > 
> > The machine default interrupt modes depends on the version. Current
> > settings are:
> > 
> >     pseries   default interrupt mode
> > 
> >     4.1       dual
> >     4.0       xics
> >     3.1       xics
> >     3.0       legacy xics (different IRQ number space layout)
> > 
> > Signed-off-by: Cédric Le Goater <clg@kaod.org>
> > Message-Id: <20190522074016.10521-3-clg@kaod.org>
> > Reviewed-by: Greg Kurz <groug@kaod.org>
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  hw/ppc/spapr.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index 39e698e9b0..4fd16b43f0 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -4352,7 +4352,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
> >      smc->default_caps.caps[SPAPR_CAP_LARGE_DECREMENTER] = SPAPR_CAP_ON;
> >      smc->default_caps.caps[SPAPR_CAP_CCF_ASSIST] = SPAPR_CAP_OFF;
> >      spapr_caps_add_properties(smc, &error_abort);
> > -    smc->irq = &spapr_irq_xics;
> > +    smc->irq = &spapr_irq_dual;
> >      smc->dr_phb_enabled = true;
> >  }
> >  
> > @@ -4430,6 +4430,7 @@ static void spapr_machine_4_0_class_options(MachineClass *mc)
> >      spapr_machine_4_1_class_options(mc);
> >      compat_props_add(mc->compat_props, hw_compat_4_0, hw_compat_4_0_len);
> >      smc->phb_placement = phb_placement_4_0;
> > +    smc->irq = &spapr_irq_xics;
> >  }
> >  
> >  DEFINE_SPAPR_MACHINE(4_0, "4.0", false);
> > 
> 
> This patch breaks the '-no-reboot' parameter (I think the "dual" mode
> breaks the -no-reboot parameter)
> 
> After grub loads the kernel and starts it, the kernel aborts:
> 
> OF stdout device is: /vdevice/vty@71000000
> Preparing to boot Linux version 4.18.0-112.el8.ppc64le
> (mockbuild@ppc-061.build.eng.bos.redhat.com) (gcc version 8.3.1 20190507
> (Red Hat 8.3.1-4) (GCC)) #1 SMP Fri Jul 5 11:21:28 UTC 2019
> Detected machine type: 0000000000000101
> command line: BOOT_IMAGE=/vmlinuz-4.18.0-112.el8.ppc64le
> root=/dev/mapper/rhel_ibm--p8--kvm--03--guest--02-root ro
> crashkernel=auto rd.lvm.lv=rhel_ibm-p8-kvm-03-guest-02/root
> rd.lvm.lv=rhel_ibm-p8-kvm-03-guest-02/swap
> Max number of cores passed to firmware: 256 (NR_CPUS = 2048)
> Calling ibm,client-architecture-support...[lvivier@localhost ~]$
> 
> I bisected to this patch, and then after I understood the problem is
> with the -no-reboot parameter as the machine is reset by the CAS
> negotiation... and the -no-reboot prevents this reset.
> 
> I don't know if it's a real problem or not.

Ah, bother.  I didn't think of the interaction between the CAS reboot
and -no-reboot.  I guess that's more reason to work out a way to do
the xics/xive switch without a full reset.  People were already not
thrilled with the extra reboots here.

-- 
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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