Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do

From	Paolo Bonzini <pbonzini@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do
Date	2016-02-08 17:50 +0100
Message-ID	<qZXaF-7Ql-7@gated-at.bofh.it> (permalink)
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On 08/02/2016 17:33, Bruce Rogers wrote:
>>> >> 
>>> >> KVM_MP_STATE_INIT_RECEIVED is what Intel calls the "wait for SIPI"
>>> >> state.  The BSP never gets a SIPI, it goes straight to 0xFFFFFFF0
>>> >> instead.  Can you explain the problem more in detail?
>> > 
>> > I suspect this is about sending INIT-SIPI from another CPU, directed to
>> > the BSP, isn't it? We may have to differentiate between CPU (including
>> > system) reset and that IPI case.
> That is correct. In looking over the KVM code which deals with BSP, this was
> the only place which seemed wrong to me wrt special casing for BSP outside the
> context of initial system initialization / reset. As far as I understand the
> BSP shouldn't be treated differently in this case.

See 8.4.2 of the SDM:

If the MP protocol has completed and a BSP is chosen, subsequent INITs
(either to a specific processor or system wide) do not cause the MP
protocol to be repeated. Instead, each logical processor examines its
BSP flag (in the IA32_APIC_BASE MSR) to determine whether it should
execute the BIOS boot-strap code (if it is the BSP) or enter a
wait-for-SIPI state (if it is an AP).

So it is correct to treat the BSP differently here, I think.

Paolo

Thread

[PATCH 1/2] KVM: x86: fix ordering of cr0 initialization code in vmx_cpu_reset Bruce Rogers <brogers@suse.com> - 2016-02-04 00:20 +0100
  [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do Bruce Rogers <brogers@suse.com> - 2016-02-04 00:20 +0100
    Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do Paolo Bonzini <pbonzini@redhat.com> - 2016-02-08 16:20 +0100
      Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do Jan Kiszka <jan.kiszka@web.de> - 2016-02-08 16:30 +0100
        Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like  APs do "Bruce Rogers" <brogers@suse.com> - 2016-02-08 17:40 +0100
          Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do Paolo Bonzini <pbonzini@redhat.com> - 2016-02-08 17:50 +0100
            Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like  APs do "Bruce Rogers" <brogers@suse.com> - 2016-02-08 18:30 +0100
              Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do Paolo Bonzini <pbonzini@redhat.com> - 2016-02-08 18:50 +0100
            Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like  APs do "Bruce Rogers" <brogers@suse.com> - 2016-02-08 18:40 +0100
              Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do Jan Kiszka <jan.kiszka@web.de> - 2016-02-08 19:00 +0100
  Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization code in vmx_cpu_reset Nadav Amit <nadav.amit@gmail.com> - 2016-02-04 00:20 +0100
    Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization  code in vmx_cpu_reset "Bruce Rogers" <brogers@suse.com> - 2016-02-04 00:40 +0100
  Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization code in  vmx_cpu_reset Paolo Bonzini <pbonzini@redhat.com> - 2016-02-08 16:10 +0100
    Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization  code in vmx_cpu_reset "Bruce Rogers" <brogers@suse.com> - 2016-02-08 17:30 +0100
      Re: [PATCH 1/2] KVM: x86: fix ordering of cr0 initialization code in  vmx_cpu_reset Paolo Bonzini <pbonzini@redhat.com> - 2016-02-08 17:50 +0100

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