Xen devel - Feb 2006 - A question about TLS libraries in case of Xen integration in Linux

The current Xen hypervisor (v3.0.1) doesn''t support TLS library.
In case of an hypothetical integration of Xen in Linux and also in 
distributions
such as RHEL5, SuSE, etc... this restriction becomes unacceptable.

So my question is:
There is a plan to support TLS library in the future or there is a plan
to integrate a Xen compatible TLS library in Linux ?

Philippe Berthault.


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On Tue, 21 Feb 2006, Philippe Berthault wrote:
> The current Xen hypervisor (v3.0.1) doesn''t support TLS library.
Are you sure?  ISTR it just flipping the segment on every fault,
and incurring a slowdown.
> There is a plan to support TLS library in the future or there is a plan
> to integrate a Xen compatible TLS library in Linux ?
Fedora Core 4 and 5 have such a glibc variant.  Other distributions
may have it too.

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Sorry if this was already replied to by someone...
> > The current Xen hypervisor (v3.0.1) doesn''t support TLS
library.
>
> Are you sure?  ISTR it just flipping the segment on every fault,
> and incurring a slowdown.
Yep.
> > There is a plan to support TLS library in the future or there is a
plan
> > to integrate a Xen compatible TLS library in Linux ?
>
> Fedora Core 4 and 5 have such a glibc variant.  Other distributions
> may have it too.
Fedora''s glibc switches off the TLS negative segment accesses (and uses
conventional accesses) when running on Xen.  SuSE''s glibc variant just 
doesn''t implement TLS accesses using negative segment offsets on any
system,
so it also supports Xen just fine. [the SuSE guys don''t think using
negative
segment offsets gives a significant performance increase for them, so they 
chose to avoid the inconvenience entirely]

On 64-bit systems, the TLS implementations used by Linux are a non-issue 
anyhow.

Cheers,
Mark

-- 
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Mark: To answer a question with a question: What use is a skateboard?
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