Re: 答复: [PATCH v1 1/2] system/cpus: Fix pause_all_vcpus() under concurrent environment

[David Hildenbrand <david@redhat.com>]

On 19.03.24 15:23, Peter Maydell wrote:
> On Tue, 19 Mar 2024 at 09:24, David Hildenbrand <david@redhat.com> wrote:
>> I spotted new pause_all_vcpus() / resume_all_vcpus() calls in hw/intc/arm_gicv3_kvm.c and
>> thought they would be the problematic bit.
>>
>> Yeah, that's going to be problematic. Further note that a lot of code does not expect
>> that the BQL is suddenly dropped.
> 
> Agreed; we already have one nasty set of bugs in the framebuffer
> devices because a function drops the BQL briefly:
> https://lore.kernel.org/qemu-devel/CAFEAcA9odnPo2LPip295Uztri7JfoVnQbkJ=Wn+k8dQneB_ynQ@mail.gmail.com/T/#u
> so let's avoid introducing any more of a similar kind.
> 
> Side note, the pause_all_vcpus()/resume_all_vcpus() calls in
> hw/i386/vapic.c are probably a bit suspect for similar reasons.

Exactly my thoughts. But there, it was less clear "why" it is even 
required. It's only performed for KVM.

Do we also just want to stop KVM threads from executing instructions?, 
so blocking KVM ioctls might be a reasonable "replacement"? Really not sure.

-- 
Cheers,

David / dhildenb