Re: [PATCH] x86-64: espfix for 64-bit mode *PROTOTYPE*

Borislav Petkov
2014-04-22T14:47:10Z

On Tue, Apr 22, 2014 at 01:23:12PM +0200, Borislav Petkov wrote:
> I wonder if it would be workable to use a bit in the espfix PGD to
> denote that it has been initialized already... I hear, near NX there's
> some room :-)

Ok, I realized this won't work when I hit send... Oh well.

Anyway, another dumb idea: have we considered making this lazy? I.e.,
preallocate pages to fit the stack of NR_CPUS after smp init is done but
not setup the percpu espfix stack. Only do that in espfix_fix_stack the
first time we land there and haven't been setup yet on this cpu.

This should cover the 1% out there who still use 16-bit segments and the
rest simply doesn't use it and get to save themselves the PT-walk in
start_secondary().

Hmmm...

--
Regards/Gruss,
Boris.

Sent from a fat crate under my desk. Formatting is fine.
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