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by crest
3475 days ago
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The x86 instruction set wasn't designed with hardware virtualisation in mind. Some of its instructions are defined to leak state from higher privileged levels into lower privileged levels. As hypervisor Xen must preserve these semantics. One way to achieve this is to trap all possible leaks and emulate the leak in the hypervisor. This is what Xen tried and failed to implement correctly. An other possible solution to similar problems is to complicate the CPU even further and have it virtualise the corner cases in hardware or microcode. |
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