linux-kernel - Re: [PATCH 3/3] x86, extable: Handle early exceptions

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Message-ID: <20120419173802.GI3221@aftab.osrc.amd.com>
Date:	Thu, 19 Apr 2012 19:38:02 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 3/3] x86, extable: Handle early exceptions

On Thu, Apr 19, 2012 at 10:27:09AM -0700, Linus Torvalds wrote:
> On Thu, Apr 19, 2012 at 10:02 AM, H. Peter Anvin <hpa@...or.com> wrote:
> >
> > ... and I would be *even happier* with an O(1) hash (which pretty much
> > *have* to be constructed at compile time.)
> 
> Taking relocations into account might be interesting for hashing. I
> guess you could hash the relative offsets, though.
> 
> But yeah, a hash might be the way to go, and once you generate the
> tables at compile-time, why not go all the way? It doesn't need to be
> some complex perfect hash, it should be fairly straightforward to just
> size the hash right and use some simple linear probing model for
> collissions or whatever.

Yeah, simplicity is the key here. I don't think we're getting that many
early boot exceptions due to rdmsr or whatever to warrant adding a bunch
of code.

OTOH, if we can share early and normal exception handling lookup code, then a
perfect hash would make sense as those exceptions would pile up.

-- 
Regards/Gruss,
Boris.

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