Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1676670

Re: [PATCH v6 3/4] KVM: async_pf: Force a nested vmexit if the injected #PF is async_pf

Show all headers | View raw

On 28/06/2017 15:38, Radim Krčmář wrote:
>> Radim, Wanpeng,
>>
>> the patch is nice now but I'm still not 100% sure about the live
>> migration part.  Why do we need to pass nested_apf to userspace, but not
>> nested_apf_token?
>
> We do not need it for migration, but unavailable nested_apf_token
> already breaks checkpoint & restore from userspace ... I think the
> cleanest way would be to add a new paravirtual event for nested_apf.
> (Or just keep delaying the apf.)

Indeed.  With Jim's plans to migrate nested virt data, I was wondering
if nested_apf and nested_apf_token would be better placed in that ioctl,
rather than GET/SET_VCPU_EVENTS.

Nested-virt migration is broken anyway until we have Jim's patches, so
there's little point in migrating nested_apf only.  Do you agree?

> Migration does a "async-pf-broadcast" while setting the async-pf MSR on
> destination, which resumes all async-pf waiters.
> Userspace actually has to drop the async-pf event on migration, because
> the destination has invalid nested_apf_token.  (It's a horrible design.)

Yes, this was my question essentially.  I would still migrate
nested_apf_token (as part of nested virt state), and then clear it in
KVM when doing the async-pf broadcast.

Paolo

> nested_apf is not #PF: if we didn't pass nested_apf, then the exception
> would be injected as #PF to L2 after migration.  (Local KVM could
> remember that the #PF is nested_apf and do some ugly hacks.)

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v6 0/4] KVM: async_pf: Fix async pf exception injection Wanpeng Li <kernellwp@gmail.com> - 2017-06-28 14:30 +0200
  [PATCH v6 3/4] KVM: async_pf: Force a nested vmexit if the injected #PF is async_pf Wanpeng Li <kernellwp@gmail.com> - 2017-06-28 14:30 +0200
    Re: [PATCH v6 3/4] KVM: async_pf: Force a nested vmexit if the  injected #PF is async_pf Paolo Bonzini <pbonzini@redhat.com> - 2017-06-28 15:00 +0200
      Re: [PATCH v6 3/4] KVM: async_pf: Force a nested vmexit if the  injected #PF is async_pf Radim Krčmář <rkrcmar@redhat.com> - 2017-06-28 15:40 +0200
        Re: [PATCH v6 3/4] KVM: async_pf: Force a nested vmexit if the  injected #PF is async_pf Paolo Bonzini <pbonzini@redhat.com> - 2017-06-28 15:50 +0200
          Re: [PATCH v6 3/4] KVM: async_pf: Force a nested vmexit if the  injected #PF is async_pf Wanpeng Li <kernellwp@gmail.com> - 2017-06-28 16:10 +0200
            Re: [PATCH v6 3/4] KVM: async_pf: Force a nested vmexit if the  injected #PF is async_pf Wanpeng Li <kernellwp@gmail.com> - 2017-06-28 16:20 +0200
              Re: [PATCH v6 3/4] KVM: async_pf: Force a nested vmexit if the  injected #PF is async_pf Wanpeng Li <kernellwp@gmail.com> - 2017-06-28 16:30 +0200
              Re: [PATCH v6 3/4] KVM: async_pf: Force a nested vmexit if the  injected #PF is async_pf Paolo Bonzini <pbonzini@redhat.com> - 2017-06-28 16:30 +0200
            Re: [PATCH v6 3/4] KVM: async_pf: Force a nested vmexit if the  injected #PF is async_pf Paolo Bonzini <pbonzini@redhat.com> - 2017-06-28 16:20 +0200
  [PATCH v6 1/4] KVM: x86: Simple kvm_x86_ops->queue_exception parameter Wanpeng Li <kernellwp@gmail.com> - 2017-06-28 14:30 +0200

csiph-web