Hi, Dose Shadow Page Table use reserved-bit (PFEC_reserved_bit) in Xen 3.3.0? In my test many page fault set reserved-bit. But I can't understand its function, after reading SPT's page-fault handler. Thanks, Wu _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
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@citrix.com> Principal Software Engineer, Citrix Systems (R&D) Ltd. [Company #02300071, SL9 0DZ, UK.] _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Thanks very much! 在2009-09-01，"Tim Deegan" <Tim.Deegan@citrix.com> 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@citrix.com> >Principal Software Engineer, Citrix Systems (R&D) Ltd. >[Company #02300071, SL9 0DZ, UK.] > >_______________________________________________ >Xen-devel mailing list >Xen-devel@lists.xensource.com >http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel