Re: [Xen-devel] Is exposing shared_info to user-land secure?

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Keir Fraser wrote:
> I think it might be okay. One issue is that how to let the user-space
> process know what vcpu it is running on, so it can use the correct timestamp
> info in a way that is safe against preemption. Bear in mind that the user
> address space may be shared by multiple concurrent threads on different
> VCPUs! If you assume consistent-tsc across all CPUs then the task is easier,
> but I don't think we'll want to bake that assumption into guest kernels and
> their interface to user processes.
>   
x86-64 already exports the current cpu and nodeid in the limit of a gdt 
entry, so you can fetch it from userspace with lsl.
   J

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