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

From: H. Peter Anvin
Date: Thu Sep 11 2008 - 16:08:46 EST


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
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