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

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Message-ID: <48C979D3.5000308@zytor.com>
Date:	Thu, 11 Sep 2008 13:04:35 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Dean Nelson <dcn@....com>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alan Mayer <ajm@....com>, Ingo Molnar <mingo@...e.hu>,
	jeremy@...p.org, rusty@...tcorp.com.au, suresh.b.siddha@...el.com,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Yinghai Lu <Yinghai.lu@....com>
Subject: Re: [RFC 0/4] dynamically allocate arch specific system vectors

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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