Re: [Qemu-devel] [PATCH 3/3] apic: always update the in-kernel status after loading

[Jan Kiszka <jan.kiszka@web.de>]

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On 2012-10-30 15:16, Paolo Bonzini wrote:
> Il 30/10/2012 13:38, Avi Kivity ha scritto:
>> On 10/30/2012 02:16 PM, Paolo Bonzini wrote:
>>> The LAPIC is loaded separately from the rest of the VCPU state.  Thus,
>>> when restoring the CPU the dummy post-reset state is passed to the
>>> in-kernel APIC.
>>>
>>> This can cause MSI injection to fail if attempted during the restore of
>>> another device, because the LAPIC believes it's not enabled.
>>>
>>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>> ---
>>>  hw/apic_common.c |    1 +
>>>  1 files changed, 1 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/hw/apic_common.c b/hw/apic_common.c
>>> index f373ba8..1ef52b2 100644
>>> --- a/hw/apic_common.c
>>> +++ b/hw/apic_common.c
>>> @@ -362,6 +362,7 @@ static int apic_dispatch_post_load(void *opaque, int version_id)
>>>      if (info->post_load) {
>>>          info->post_load(s);
>>>      }
>>> +    cpu_put_apic_state(DEVICE(s));
>>>      return 0;
>>>  }
>>
>> Aren't we still dependent on the order of processing?  If the APIC is
>> restored after the device, won't we get the same problem?
> 
> Strictly speaking yes, but CPUs and APICs are always the first devices
> to be saved.

Hmm, thinking about this again: Why is the MSI event injected at all
during restore, specifically while the device models are in transitional
state. Can you explain this? Does the same pattern then also apply on
INTx injection?

Jan



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