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


From: Cédric Le Goater
Subject: Re: [Qemu-devel] [Qemu-ppc] [PULL 41/44] spapr: change default interrupt mode to 'dual'
Date: Mon, 15 Jul 2019 12:19:03 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2

On 11/07/2019 03:26, David Gibson wrote:
> 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 <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.
> 
> 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.

QEMU builds a device tree depending on the interrupt mode negotiated 
at CAS time. Can we dynamically add/remove nodes ?

C.



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