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

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Date:	Mon, 04 Jan 2010 16:05:44 -0800
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Yinghai Lu <yinghai@...nel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Jesse Brandeburg <jesse.brandeburg@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	NetDEV list <netdev@...r.kernel.org>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>
Subject: Re: Subject: [PATCH 1/2] x86: get back 15 vectors

On Mon, 2010-01-04 at 11:50 -0800, H. Peter Anvin wrote:
> On 01/04/2010 11:45 AM, Suresh Siddha wrote:
> > On Mon, 2010-01-04 at 11:35 -0800, Yinghai Lu wrote:
> >> sth like this?
> >>
> >> Subject: [PATCH 1/2] x86: get back 16 vectors
> >>
> >> -v2: according to hpa that we could start from 0x10
> >>      according to Eric, we should hold 16 vectors for IRQ MOVE
> >>
> >> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> >>
> > 
> > Yinghai we have to change IRQ_MOVE_CLEANUP_VECTOR to 0x1f or so. From
> > the cpu perspective this vector is documented as illegal, so we need to
> > check if this change will work on the cpu's we have today to get some
> > confidence.
> > 
> 
> It's documented as reserved, not illegal.  The ability for the APIC to
> generate vectors starting at 0x10 is documented, as is the ability for
> the CPU to receive any vector number as an interrupt -- in fact, the
> legacy BIOS relies on being able to receive interrupts starting at
> vector 0x08.  It causes problems galore, but only at the software level.

I have checked out couple of platforms (including 32-bit atom) and 0x1f
vector logic seems to be working.

Hopefully we won't have other hardware or software issues (vmm
restrictions etc) with this logic.

thanks,
suresh

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