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xen-devel
Re: [Xen-devel] wget and Zope crashes on post-2.0.6 -testing
Hi all
Keir Fraser wrote:
When set it causes a fault whenever the FPU is accessed. We use it to
lazily initialise the FPU for the currently running process. At
context-switch time we look at the process we are descheduling and, if
it hasn;t used the FPU in its time slice, we don;t save FPU state and we
don;t set the TS bit (because we assume it must be already set).
The last point is where we can fall down: if the TS bit in fact *isn;t*
set, then we are screwed for all time. The kernel will never realise a
process is using the FPU because we will never take the TS fault,
because the TS bit is clear. Thus state doesn;t get saved/restored
during context switch and the TS bit never gets set. So its a self
perpetuating state once you're in it.
I have an end user question rather than a developers Q.
Say I have an xen machine with several domains, some with kernels
that have the FPU bug fix and some without. Can a domain with
the buggy kernel upset a domain with a bug free kernel?
Or does this just affect processes within one domain?
I might want to be a bit more hasty in upgrading all the kernels
if a buggy kernel/domain can upset a good kernel/domain.
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