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

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.


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