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

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Date:	Tue, 22 Apr 2014 16:40:51 -0700
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Andi Kleen <andi@...stfloor.org>, "H. Peter Anvin" <hpa@...or.com>
CC:	Brian Gerst <brgerst@...il.com>,
	Andrew Lutomirski <amluto@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.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>,
	Arjan van de Ven <arjan.van.de.ven@...el.com>,
	Alexandre Julliard <julliard@...ehq.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86-64: espfix for 64-bit mode *PROTOTYPE*

On 04/22/2014 04:39 PM, Andi Kleen wrote:
>> That simply will not work if you can take a #GP due to the "safe" MSR
>> functions from NMI and #MC context, which would be my main concern.
> 
> At some point the IST entry functions subtracted 1K while the
> handler ran to handle simple nesting cases.
> 
> Not sure that code is still there.

Doesn't help if you take an NMI on the first instruction of the #GP handler.

	-hpa


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