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Re: [PATCH v3 0/8] Generalize start-powered-off property from ARM

From: Philippe Mathieu-Daudé
Subject: Re: [PATCH v3 0/8] Generalize start-powered-off property from ARM
Date: Mon, 17 Aug 2020 07:24:43 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0

On 8/17/20 6:47 AM, David Gibson wrote:
> On Wed, Jul 22, 2020 at 11:56:49PM -0300, Thiago Jung Bauermann wrote:
>> The ARM code has a start-powered-off property in ARMCPU, which is a
>> subclass of CPUState. This property causes arm_cpu_reset() to set
>> CPUState::halted to 1, signalling that the CPU should start in a halted
>> state. Other architectures also have code which aim to achieve the same
>> effect, but without using a property.
>> The ppc/spapr version has a bug where QEMU does a KVM_RUN on the vcpu
>> before cs->halted is set to 1, causing the vcpu to run while it's still in
>> an unitialized state (more details in patch 3).
>> Peter Maydell mentioned the ARM start-powered-off property and
>> Eduardo Habkost suggested making it generic, so this patch series does
>> that, for all cases which I was able to find via grep in the code.
>> The only problem is that I was only able to test these changes on a ppc64le
>> pseries KVM guest, so except for patches 2 and 3, all others are only
>> build-tested. Also, my grasp of QOM lifecycle is basically non-existant so
>> please be aware of that when reviewing this series.
>> The last patch may be wrong, as pointed out by Eduardo, so I marked it as
>> RFC. It may make sense to drop it.
>> Applies cleanly on yesterday's master.
> This series appears to break the Travis build for a MIPS target:
> Unexpected error in qdev_prop_set_after_realize() at 
> /home/travis/build/dgibson/qemu/hw/core/qdev-properties.c:30:
> qemu-system-mips64el: Attempt to set property 'start-powered-off' on 
> anonymous device (type 'I6400-mips64-cpu') after it was realized
> Broken pipe
> /home/travis/build/dgibson/qemu/tests/qtest/libqtest.c:175: kill_qemu() 
> detected QEMU death from signal 6 (Aborted) (core dumped)
> Aborted (core dumped)
> ERROR qom-test - too few tests run (expected 8, got 0)
> /home/travis/build/dgibson/qemu/tests/Makefile.include:650: recipe for target 
> 'check-qtest-mips64el' failed

Good catch. hw/mips/cps.c, hw/ppc/e500.c and hw/sparc/sun4m.c are
incorrectly setting the property after the cpu is realized because
the cpu is created with cpu_create(). We need to create them with
object_initialize_child() and realize them manually with qdev_realize().

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