[Bug 288237] bhyve does not boot Rocky Linux 10 from ISO

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=288237

--- Comment #13 from Zhenlei Huang <zlei@FreeBSD.org> ---
(In reply to Konstantin Belousov from comment #12)
> No, if the guest issues undefined instruction, it must be reflected as the
> corresponding exception (#UD) back to the guest.  It is up to the guest code
> to handle it or not.

> Typically the loaders are very naive in handling CPU exceptions, most often
> they do not even install exception handlers.  This is even more true for UEFI
> boot envs, where UEFI started having dedicated debugger protocol.

> In other words, if loader issued an instruction that is not supported by the
> CPU (and bhyve does not emulate unsupported instructions), the result is
> typically hang or silent reboot.

Can I conclude that, only when VM-Exit events occurs, then the VMM can take
over the CPU ( so it is exiting a virtual execution mode ) ?

I did a quick look at Intel’s Software Developer Manual outlines 64 “Basic Exit
Reasons”, it appears an undefined instruction do not cause VM-Exit.

So if the guest ( either the loader or kernel ) do not handle the event of
undefined instruction ( print to console or hand it over to VMM explicitly, say
via vmexit ), the VMM is hopeless to have a chance to log the `undefined
instruction` event ?

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