Re: [PATCH v2 0/3] KVM: PPC: BookE: Fix boot hang on preemptible kernels

[Christian Zigotzky <chzigotzky@xenosoft.de>]

On 10/11/26 06:32, Shrikanth Hegde wrote:
> Christian Zigotzky had reported that preemptible kernels don't boot on
> his FSL Cyrus+ board. The board freezes on running either full/lazy
> preemption and has been an issue for a while now (years!).
>
> https://lore.kernel.org/all/b897b0fd-90f2-4215-bcd4-3714e497d773@xenosoft.de/#t
>
> After 7.0, there is only preempt=full/lazy which removed the
> preempt=none/voluntary workaround used to mask the issue. There was
> challenge is getting the console logs which made the fixes difficult since
> one couldn't know where the issue is.
>
> Thanks to Michal for helping in getting the logs. That pointed at few
> places where the issue could be. This series is an attempt at fixing
> those.
>
> Christian, I haven't taken the tested-by tag since patches have
> changed quite a bit.
> Please help in *testing* the patches again.
>
> v1->v2:
> - Re-order to avoid preempt count dance (Narayana Murty N)
> - Do only hard_irq_disable on PPC64 to avoid second warning. On PPC32
>    use local_irq_disable to acheive the same. (Ritesh Harjani)
>
> v1: https://lore.kernel.org/all/20260928110411.844582-1-sshegde@linux.ibm.com/
>
> New API ppc_hard_irq_disable could potentially be used in other places.
> There is similar pattern of doing both local and hard irq disable and
> likely not all callsites need both. But it is a larger effort and due to
> my time limit, it will be taken up subsequently.
>
> Shrikanth Hegde (3):
>    powerpc/irq: Add ppc_hard_irq_disable()
>    KVM: PPC: BookE: Load FP and Altivec before enabling the interrupts
>    KVM: PPC: Use ppc_hard_irq_disable before guest entry
>
>   arch/powerpc/include/asm/hw_irq.h | 17 +++++++++++++++++
>   arch/powerpc/kvm/booke.c          |  7 +++++--
>   arch/powerpc/kvm/powerpc.c        | 14 +++-----------
>   3 files changed, 25 insertions(+), 13 deletions(-)
>

I patched the RC2 of kernel 7.4 with these three new patches and 
compiled it again [1]. The patched RC2 preempt kernel works with KVM HV 
without any problems.

Tested-by: Christian Zigotzky <chzigotzky@xenosoft.de>

Thanks a lot for your help! :-)

[1] https://github.com/chzigotzky/kernels/releases/tag/v7.4.0-rc2-2

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