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Re: [Xen-devel] Paravirtualization of the "HLT" instruction (for example) on x386

On 24 Jan 2006, at 12:24, Ian Brown wrote:

you mean that GPFs that occurred in ring 1 will be handled at the first
place by the guest ? (or ,what seems to me more unlikely, first by ring0
and then somehow "passed" to the guest)

That is what happens. The processor does not discriminate between GPFs -- they must all be delivered to the same initial handler. That handler is the one in Xen in ring 0. Xen then virtualises the GPF to the OS in ring 1 if Xen does not want to handle it itself. It does this by creating a suitable exception frame on the guest stack and jumping at the guest's registered GPF handler.

 -- Keir

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