Re: Re: "Barry Silverman": Setting GDT entries for Thread Local Storage

[Zachary Amsden <zamsden@cisco.com>]

Keir Fraser wrote:

>>I am trying to port the Fedora version of Linux to xeno-linux. It involves
>>porting the NPTL Library (New Posix Thread Library), and TLS (Thread Local
>>Storage) kernel changes which Redhat backported from 2.6 into 2.4.
>>
>>    
>>
>...
>This shoudl all work straightforwardly, unless TLS tries to install
>segments that are "full size" (i.e. 4GB). I know that one of the
>recent glibc threading solutions tries to do this --- it won't work
>with Xen because we clip segments so that they do not overlap with
>Xen's reserved area in the top 64MB of the virtual address space.
>  
>
I don't want to throw a monkeywrench in your plans, but another 
potential trouble spot is the x86 vsyscall interface in 2.6.  The 
vsyscall region sits at the top of the virtual address space, and could 
conflict with the Xen mapping.  You may have to consider remapping Xen 
to another memory region, but I'm not sure where there may be other 
trouble areas with Windows domains (map?).  At some point in the 
forseeable future, it might no longer be possible to locate Xen at an OS 
neutral location, so perhaps it is worth considering the remapping 
problem now.

Zachary Amsden
zamsden@cisco.com


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