Re: [RFC 0/4] dynamically allocate arch specific system vectors

H. Peter Anvin
2008-09-11T20:08:46Z

Dean Nelson wrote:
>
> We (SGI) need somewhere around eight vectors.
>
> There are two kernel modules, sgi-gru and sgi-xp (in drivers/misc), that
> each need two vectors. And there's the broadcast assist unit (BAU) that is
> involved in tlb shootdown on uv, which currently uses statically reserved
> vector 0xf8 (UV_BAU_MESSAGE -- see uv_bau_init()). I know of a debugger that
> also uses 0xf8 because it was previously available until UV_BAU_MESSAGE came
> along. The BAU would be happy with a dynamically allocated system vector.
> We have a couple of other things in the works that also need vectors.
>
> All of these eight or so vectors are only meaningful on SGI uv systems.
>

Are these kernel-internal vectors, or exposed to userspace (i.e. the INT
instruction works in userspace)? From what I'm gathering, I think this
is the former.

There are the occational user who wants fixed user-space addressible
vectors, effectively as secondary system call entry vectors (lguest is
the only in-kernel user that I know of); those need to be static and
non-conflicting, which is kind of difficult. It seems to me that
anything else probably should be possible to be dynamic.

-hpa