Re: vmcall time

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

Omar Khan wrote:
> Anthony Liguori <anthony@...> writes:
>
>   
>> I've got a patch that should appear in virtbench soon that actually 
>> measures vmcall latency.
>>
>> http://ozlabs.org/~rusty/virtbench
>>
>>     
>
> Thanks Anthony. I have a newbie question though. In the vmcall function in the
> patch:
>
> +static int vmcall(unsigned int cmd)
> +{
> +	signal(SIGILL, illegal_instruction);
> +	asm volatile(".byte 0x0F,0x01,0xC1,0xC3\n" ::"a"(cmd));
> +	signal(SIGILL, SIG_DFL);
> +
> +	return 0;
> +}
>
> Why do you have the ret opcode '0xC3' with the vmcall? 
>   

Because I lazily copied from KVM instead of looking them up.  I figured 
0xC3 was a NOP.  Will fix.

> Thanks
>
> Omar 
>
>
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