Re: Re: [Xen-devel] question about system call mechanism in xen

["Zang Hongyong" <zanghongyong@xxxxxxxxxx>]

======= 2008-03-17 22:57:46 您在来信中写道：=======

>>>> "Zang Hongyong" <zanghongyong@xxxxxxxxxx> 17.03.08 15:02 >>>
>>hi,
>>  I'm interested in system call mechanism in Xen. My understanding (guess) as 
>> follows.
>>   1)When user application makes a system call, a "int 80" will occur. 
>>   2)Then trap to Ring 0 (Which is hypervisor's location). 
>>   3)Then hypervisor redirect it to Guest OS's kernel to do system call 
>> operation.
>>   4)Then back to Ring 0
>>   5)back to user appliction
>>
>>  Is that true?
>
>If everything is 32-bit, "int 80" will be used, but it'll be directed directly
>to the guest kernel in ring 1 (i.e. the hypervisor isn't involved).
Many thanks
yet the words "directed directly" equals "fast trap" which appears in "Xen and 
the Art of Virtualization". 
Right? 
"Fast trap" is implemented in this way that systemcall's item in IDT of 
hypervisor points to Guest's kernel operation.
Right?


>If the hypervisor is 64-bit, things behave differently based upon what
>kind of kernel/app you're running and whether it's a AMD or Intel CPUs
>the system is equipped with.
>
>>  Where can I get documents about this question in detail?
>
>Source code is probably the only reference.
>
>Jan
>
>
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　　　　　　　　致
礼！
 
                                 
　　　　　　　　Zang Hongyong
　　　　　　　　zanghongyong@xxxxxxxxxx
　　　　　　　　　　2008-03-18

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