Re: [RFC] fix VMX TSC synchronicity

Avi Kivity
2008-05-06T13:55:19Z

Avi Kivity wrote:
> [Resurrecting post from the dead]
>
>
> Marcelo Tosatti wrote:
>> Forcing clustered APIC mode works only on SMP, and there were high CPU
>> consumption on Windows SMP guests due to C3 state being reported (fixed
>> in kvm-30 something).
>>
>> So perhaps:
>> - Faking clustered APIC on SMP - Faking C3 on UP
>>
>> And turning of the TSC bit (for 32-bit guests).
>>
>> Is the way to go?
>> Avi, do you understand why C3 was causing the Windows SMP problems ?
>>
>>
>
> It's probably inb()ing on the port in a loop. It's not SMP causing
> the problems, but the ACPI HAL. I'll check this.
>

Yes, it's reading 0xb010 and 0xb014, which ought to place the cpu in
sleep mode, but don't.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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