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

[Laurent Vivier]

On 29/05/2019 08:50, David Gibson wrote:
> From: Cédric Le Goater <address@hidden>
> 
> 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 <address@hidden>
> Message-Id: <address@hidden>
> Reviewed-by: Greg Kurz <address@hidden>
> Signed-off-by: David Gibson <address@hidden>
> ---
>  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
(address@hidden) (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.

Thanks,
Laurent