Re: [Qemu-devel] [PATCH 0/2 v3] kvm: notify host when guest panicked

[Wen Congyang <wency@cn.fujitsu.com>]

At 03/22/2012 03:12 AM, Anthony Liguori Wrote:
> On 03/15/2012 06:46 AM, Avi Kivity wrote:
>> On 03/15/2012 01:25 PM, Jan Kiszka wrote:
>>>>>
>>>> There was such vm exit (KVM_EXIT_HYPERCALL), but it was deemed to be a
>>>> bad idea.
>>>
>>> BTW, this would help a lot in emulating hypercalls of other hypervisors
>>> (or of KVM's VAPIC in the absence of in-kernel irqchip - I had to jump
>>> through hoops therefore) in user space. Not all those hypercall handlers
>>> actually have to reside in the KVM module.
>>>
>>
>> That is true.  On the other hand the hypercall ABI might go to pieces if
>> there was no central implementation.
> 
> Just declare that outl 0x505 is a megaultracall and s/vmcall/outb/g and
> call it a day.

Why use 0x505? Is it a reserved port, and it will not be used by any device?

How can I get all reserved port?

Thanks
Wen Congyang

> 
> The performance difference between vmcall and outl is so tiny compared
> to the cost of dropping to userspace that it really doesn't matter which
> instruction is used.
> 
> Regards,
> 
> Anthony Liguori
> 
>>
> 
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