Date: Tue, 22 Apr 2014 16:46:59 +0200
From: Borislav Petkov <bp@alien8.de>
To: Andrew Lutomirski <amluto@gmail.com>, "H. Peter Anvin" <hpa@zytor.com>
Cc: "H. Peter Anvin" <hpa@linux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        Alexander van Heukelum <heukelum@fastmail.fm>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Arjan van de Ven <arjan.van.de.ven@intel.com>,
        Brian Gerst <brgerst@gmail.com>,
        Alexandre Julliard <julliard@winehq.com>,
        Andi Kleen <andi@firstfloor.org>, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] x86-64: espfix for 64-bit mode *PROTOTYPE*
Message-ID: <20140422144659.GF15882@pd.tnic>
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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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