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Re: [Xen-devel] context switch

On 28 Mar 2006, at 18:40, Keir Fraser wrote:

Why is it expensive? The updates to zero only happen if the previous selector value was non-zero, which is usually not the case for 64-bit apps.

Things should work okay even without the zeroing, by the way. It just avoids an unnecessary failsafe callback into the guest kernel. I fixed the failsafe handler for x86/64 earlier today.

We should probably just rely on the failsafe_handler actually (assuming it now works :-) ).

That 'slow path' will be taken so infrequently it's not worth having a special prepare_arch_switch() for Xen. It's really a hangover from the initial port from i386.

 -- Keir

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