Re: [PATCH v3 05/15] arm64: kvm: Build hyp-entry.S separately for VHE/nVHE

David Brazdil
2020-06-22T10:20:51Z

Hi Marc,

> > - void *dst = lm_alias(__bp_harden_hyp_vecs + slot * SZ_2K);
> > + char *vec = has_vhe() ? __bp_harden_hyp_vecs
> > + : kvm_nvhe_sym(__bp_harden_hyp_vecs);
>
> If we get this construct often, then something that abstracts
> the uggliness of the symbol duality would be nice...

Agreed, I do hope that this will end up being limited to finding the address of
the hyp-init vector once EL2 becomes self-contained. Even this vector selection
can be done in EL2 where the symbol duality does not exist.
If we were to hide it, there is a trade off between code "elegance" and clarity
of what's happening under the hood. I was thinking we could extract this
`has_vhe() ? foo : __kvm_nvhe_foo` as a `#define foo` but I do worry that
anybody debugging this code would be cursing my name. It would also not work
with other macros that take symbol names, notably kvm_ksym_ref. But that can be
rewritten to accept a pointer instead. The more verbose but less magic approach
is to have a bunch of different helpers for various situations, eg.
__pa_symbol_nvhe. What would be your preference?

-David