Re: [PATCH] kvm-vmx: add module parameter to avoid trapping HLT instructions (v3)

[Anthony Liguori <anthony@codemonkey.ws>]

On 12/03/2010 05:32 PM, Joerg Roedel wrote:
> On Fri, Dec 03, 2010 at 04:39:22PM -0600, Anthony Liguori wrote:
>    
>> +	if (yield_on_hlt)
>> +		min |= CPU_BASED_HLT_EXITING;
>>      
> This approach won't work out on AMD because in HLT the CPU may enter
> C1e. In C1e the local apic timer interupt is not delivered anymore and
> when this is the current timer in use the cpu may miss timer ticks or
> never comes out of HLT again. The guest has no chance to work around
> this as the Linux idle routine does.
>    

And this doesn't break old software on bare metal?

Regards,

Anthony Liguori

> If you really wan't active idling of a guest, it should idle in the
> hypervisor where it can work around such problems.
>
> 	Joerg
>
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