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

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Message-ID: <53571A7D.8050702@zytor.com>
Date:	Tue, 22 Apr 2014 18:42:21 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andrew Lutomirski <amluto@...il.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Alexander van Heukelum <heukelum@...tmail.fm>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Borislav Petkov <bp@...en8.de>,
	Arjan van de Ven <arjan.van.de.ven@...el.com>,
	Brian Gerst <brgerst@...il.com>,
	Alexandre Julliard <julliard@...ehq.com>,
	Andi Kleen <andi@...stfloor.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86-64: espfix for 64-bit mode *PROTOTYPE*

On 04/22/2014 06:23 PM, Andrew Lutomirski wrote:
> 
> What's the to_dmesg thing for?
> 

It's for debugging... the espfix page tables generate so many duplicate
entries that trying to output it via a seqfile runs out of memory.  I
suspect we need to do something like skip the espfix range or some other
hack.

> It looks sane, although I haven't checked the detailed register manipulation.
> 
> Users of big systems may complain when every single CPU lines up for
> that mutex.  Maybe no one cares.

Right now the whole smpboot sequence is fully serialized... that needs
to be fixed.

Konrad - I really could use some help figuring out what needs to be done
for this not to break Xen.

	-hpa

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