Subject: Re: Subject: [PATCH 1/2] x86: get back 15 vectors

From: "H. Peter Anvin" <[email-masked]>
Date: Mon, 04 Jan 2010 11:48:12 -0800

[Adding Suresh to the Cc: list]

On 01/04/2010 11:35 AM, Yinghai Lu wrote:
> 
> so we can use [0x10, 0x1f]
> 
> sth like this?
> 

No!!!

[0x10, 0x1f] is reserved for exceptions.  We can probably get away with
stealing *one* vector... presumably at the end (0x1f).  However, we can
absolutely not use the whole block: 0x10-0x13 is occupied by exceptions
we already have OS support for (#MF, #AC, #MC, and #XM), and it's pretty
much guaranteed we'll have more coming.  However, growth is quite slow
and since this is a kernel-internal vector (not accessible to user
space) it is not creating an API.

In other words, we could change FIRST_EXTERNAL_VECTOR to 0x1f, and use
it for IRQ_MOVE_CLEANUP_VECTOR.  Then use 0x20..0x2f for the legacy vectors.

	-hpa