Re:Re: [Xen-devel] reserved bit in ShadowPT

["Wu Bingzheng" <wubingzheng@xxxxxxx>]

Thanks very much!

在2009-09-01，"Tim Deegan" <Tim.Deegan@xxxxxxxxxx> 写道：
>At 04:29 +0100 on 01 Sep (1251779345), Wu Bingzheng wrote:
>> Hi,
>> 
>> Dose Shadow Page Table use reserved-bit (PFEC_reserved_bit) in Xen 3.3.0?
>
>Yes.  It uses reserved bits in ptes to indicate entries that are known
>to be either emulated-MMIO or not-present in the guest pagetables.  Then
>in the fault handler it can use PFEC_reserved_bit to branch onto a fast
>path for those cases without taking any locks or walking the guest
>pagetables.
>
>> In my test many page fault set reserved-bit. But I can't understand its function, after reading SPT's page-fault handler.
>
>Have a look at the definition of SH_L1E_MAGIC in arch/x86/mm/shadow/types.h
>
>Cheers,
>
>Tim.
>
>
>-- 
>Tim Deegan <Tim.Deegan@xxxxxxxxxx>
>Principal Software Engineer, Citrix Systems (R&D) Ltd.
>[Company #02300071, SL9 0DZ, UK.]
>
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