On 8 Oct 2005, at 23:39, Jonathan M. McCune wrote:
> We''re curious about page fault handling in Xen-devel. In
particular,
> during kernel boot-up, the kernel tests if the CPU "honours the WP
> bit". This causes a page fault with error code 3 (expected behavior).
> Does Xen still make a copy of the execution stack frame on the guest
> OS stack, as specified in the original "Xen and the Art of
> Virtualization" paper? There is a footnote here that suggests that
> using a pre-agreed shared memory location might be a better option.
> Has this change been implemented?
>
> After the WP-test page fault is taken, what is supposed to happen from
> Xen''s perspective on the return from the page fault handler? In
> normal linux, the exception handler changes its own return address
> (i.e., modifies the EIP register) to be the "fixup" address.
Does
> this still happen with XenoLinux, or does the hypervisor get involved?
Everything works as on native, pretty much, except that the page-fault
stack frame is extended by one word to contain the faulting linear
address (because the guest cannot directly access %cr2).
-- Keir
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